Programs & Examples On #Ruby

Ruby is a multi-platform open-source, dynamic object-oriented interpreted language, created by Yukihiro Matsumoto (Matz) in 1995. The [ruby] tag is for questions related to the Ruby language, including its syntax and its libraries. Ruby on Rails questions should be tagged with [ruby-on-rails].

How do I get the name of a Ruby class?

You want to call .name on the object's class:

result.class.name

"for" vs "each" in Ruby

(1..4).each { |i| 


  a = 9 if i==3

  puts a 


}
#nil
#nil
#9
#nil

for i in 1..4

  a = 9 if i==3

  puts a

end
#nil
#nil
#9
#9

In 'for' loop, local variable is still lives after each loop. In 'each' loop, local variable refreshes after each loop.

Pass variables to Ruby script via command line

You should try console_runner gem. This gem makes your pure Ruby code executable from command-line. All you need is to add YARD annotations to your code:

# @runnable This tool can talk to you. Run it when you are lonely.
#   Written in Ruby.  
class MyClass

    def initialize
      @hello_msg = 'Hello' 
      @bye_msg = 'Good Bye' 
    end

    # @runnable Say 'Hello' to you.
    # @param [String] name Your name
    # @param [Hash] options options
    # @option options [Boolean] :second_meet Have you met before?
    # @option options [String] :prefix Your custom prefix
    def say_hello(name, options = {})
      second_meet = nil
      second_meet = 'Nice to see you again!' if options['second_meet']
      prefix = options['prefix']
      message = @hello_msg + ', '
      message += "#{prefix} " if prefix
      message += "#{name}. "
      message += second_meet if second_meet
      puts message
    end

end

Then run it from console:

$ c_run /projects/example/my_class.rb  say_hello -n John --second-meet --prefix Mr. 
-> Hello, Mr. John. Nice to see you again!

Ruby send JSON request

It's 2020 - nobody should be using Net::HTTP any more and all answers seem to be saying so, use a more high level gem such as Faraday - Github


That said, what I like to do is a wrapper around the HTTP api call,something that's called like

rv = Transporter::FaradayHttp[url, options]

because this allows me to fake HTTP calls without additional dependencies, ie:

  if InfoSig.env?(:test) && !(url.to_s =~ /localhost/)
    response_body = FakerForTests[url: url, options: options]

  else
    conn = Faraday::Connection.new url, connection_options

Where the faker looks something like this

I know there are HTTP mocking/stubbing frameworks, but at least when I researched last time they didn't allow me to validate requests efficiently and they were just for HTTP, not for example for raw TCP exchanges, this system allows me to have a unified framework for all API communication.


Assuming you just want to quick&dirty convert a hash to json, send the json to a remote host to test an API and parse response to ruby this is probably fastest way without involving additional gems:

JSON.load `curl -H 'Content-Type:application/json' -H 'Accept:application/json' -X POST localhost:3000/simple_api -d '#{message.to_json}'`

Hopefully this goes without saying, but don't use this in production.

Parsing a JSON string in Ruby

Don't see any answers here that mention parsing directly to an object other than a Hash, but it is possible using the poorly-documented object_class option(see https://ruby-doc.org/stdlib-2.7.1/libdoc/json/rdoc/JSON.html):

JSON.parse('{"foo":{"bar": 2}}', object_class: OpenStruct).foo.bar
=> 2

The better way to read that option is "The ruby class that a json object turns into", which explains why it defaults to Hash. Likewise, there is an array_class option for json arrays.

Does Ruby have a string.startswith("abc") built in method?

It's called String#start_with?, not String#startswith: In Ruby, the names of boolean-ish methods end with ? and the words in method names are separated with an _. Not sure where the s went, personally, I'd prefer String#starts_with? over the actual String#start_with?

How to delete specific characters from a string in Ruby?

For those coming across this and looking for performance, it looks like #delete and #tr are about the same in speed and 2-4x faster than gsub.

text = "Here is a string with / some forwa/rd slashes"
tr = Benchmark.measure { 10000.times { text.tr('/', '') } }
# tr.total => 0.01
delete = Benchmark.measure { 10000.times { text.delete('/') } }
# delete.total => 0.01
gsub = Benchmark.measure { 10000.times { text.gsub('/', '') } }
# gsub.total => 0.02 - 0.04

How do I display Ruby on Rails form validation error messages one at a time?

I resolved it like this:

<% @user.errors.each do |attr, msg| %>
  <li>
    <%= @user.errors.full_messages_for(attr).first if @user.errors[attr].first == msg %>
  </li>
<% end %>

This way you are using the locales for the error messages.

Checking if a variable is not nil and not zero in ruby

unless discount.nil? || discount == 0
  # ...
end

'sudo gem install' or 'gem install' and gem locations

Better yet, put --user-install in your ~/.gemrc file so you don't have to type it every time

gem: --user-install

Append key/value pair to hash with << in Ruby

There is merge!.

h = {}
h.merge!(key: "bar")
# => {:key=>"bar"}

rails bundle clean

Honestly, I had problems with bundler circular dependencies and the best way to go is rm -rf .bundle. Save yourselves the headache and just use the hammer.

No increment operator (++) in Ruby?

From a posting by Matz:

(1) ++ and -- are NOT reserved operator in Ruby.

(2) C's increment/decrement operators are in fact hidden assignment. They affect variables, not objects. You cannot accomplish assignment via method. Ruby uses +=/-= operator instead.

(3) self cannot be a target of assignment. In addition, altering the value of integer 1 might cause severe confusion throughout the program.

                      matz.

How to drop columns using Rails migration

Clear & Simple Instructions for Rails 5 & 6

  • WARNING: You will lose data if you remove a column from your database. To proceed, see below:
  • Warning: the below instructions are for trivial migrations. For complex migrations with e.g. millions and millions of rows, you will have to account for the possibility of failures, you will also have to think about how to optimise your migrations so that they run swiftly, and the possibility that users will use your app while the migration process is occurring. If you have multiple databases, or if anything is remotely complicated, then don't blame me if anything goes wrong!

1. Create a migration

Run the following command in your terminal:

rails generate migration remove_fieldname_from_tablename fieldname:fieldtype

Note: the table name should be in plural form as per rails convention.

Example:

In my case I want to remove the accepted column (a boolean value) from the quotes table:

rails g migration RemoveAcceptedFromQuotes accepted:boolean

See the documentation re: a convention when adding/removing fields to a table:

There is a special syntactic shortcut to generate migrations that add fields to a table.

rails generate migration add_fieldname_to_tablename fieldname:fieldtype

2. Check the migration

# db/migrate/20190122035000_remove_accepted_from_quotes.rb
class RemoveAcceptedFromQuotes < ActiveRecord::Migration[5.2]
  # with rails 5.2 you don't need to add a separate "up" and "down" method.
  def change
    remove_column :quotes, :accepted, :boolean
  end
end

3. Run the migration

rake db:migrate or rails db:migrate (they're both the same)

....And then you're off to the races!

How to change Hash values?

Try this function:

h = {"a" => "b", "c" => "d"}
h.each{|i,j| j.upcase!} # now contains {"a" => "B", "c" => "D"}.

PG::ConnectionBad - could not connect to server: Connection refused

For MacOS I use this:

brew info postgres

And in output in the most end, I see:

...
To have launchd start postgresql now and restart at login:
  brew services start postgresql
Or, if you don't want/need a background service you can just run:
  pg_ctl -D /usr/local/var/postgres start

So I just use this command pg_ctl -D /usr/local/var/postgres start and psql begin work.

Create Directory if it doesn't exist with Ruby

How about just Dir.mkdir('dir') rescue nil ?

How to list all methods for an object in Ruby?

The following will list the methods that the User class has that the base Object class does not have...

>> User.methods - Object.methods
=> ["field_types", "maximum", "create!", "active_connections", "to_dropdown",
    "content_columns", "su_pw?", "default_timezone", "encode_quoted_value", 
    "reloadable?", "update", "reset_sequence_name", "default_timezone=", 
    "validate_find_options", "find_on_conditions_without_deprecation", 
    "validates_size_of", "execute_simple_calculation", "attr_protected", 
    "reflections", "table_name_prefix", ...

Note that methods is a method for Classes and for Class instances.

Here's the methods that my User class has that are not in the ActiveRecord base class:

>> User.methods - ActiveRecord::Base.methods
=> ["field_types", "su_pw?", "set_login_attr", "create_user_and_conf_user", 
    "original_table_name", "field_type", "authenticate", "set_default_order",
    "id_name?", "id_name_column", "original_locking_column", "default_order",
    "subclass_associations",  ... 
# I ran the statements in the console.

Note that the methods created as a result of the (many) has_many relationships defined in the User class are not in the results of the methods call.

Added Note that :has_many does not add methods directly. Instead, the ActiveRecord machinery uses the Ruby method_missing and responds_to techniques to handle method calls on the fly. As a result, the methods are not listed in the methods method result.

How to convert a unix timestamp (seconds since epoch) to Ruby DateTime?

One command to convert date time to Unix format and then to string

    DateTime.strptime(Time.now.utc.to_i.to_s,'%s').strftime("%d %m %y")

    Time.now.utc.to_i #Converts time from Unix format
    DateTime.strptime(Time.now.utc.to_i.to_s,'%s') #Converts date and time from unix format to DateTime

finally strftime is used to format date

Example:

    irb(main):034:0> DateTime.strptime("1410321600",'%s').strftime("%d %m %y")
    "10 09 14"

Gem Command not found

The following command may help you

sudo apt-get install ruby

ruby 1.9: invalid byte sequence in UTF-8

In Ruby 1.9.3 it is possible to use String.encode to "ignore" the invalid UTF-8 sequences. Here is a snippet that will work both in 1.8 (iconv) and 1.9 (String#encode) :

require 'iconv' unless String.method_defined?(:encode)
if String.method_defined?(:encode)
  file_contents.encode!('UTF-8', 'UTF-8', :invalid => :replace)
else
  ic = Iconv.new('UTF-8', 'UTF-8//IGNORE')
  file_contents = ic.iconv(file_contents)
end

or if you have really troublesome input you can do a double conversion from UTF-8 to UTF-16 and back to UTF-8:

require 'iconv' unless String.method_defined?(:encode)
if String.method_defined?(:encode)
  file_contents.encode!('UTF-16', 'UTF-8', :invalid => :replace, :replace => '')
  file_contents.encode!('UTF-8', 'UTF-16')
else
  ic = Iconv.new('UTF-8', 'UTF-8//IGNORE')
  file_contents = ic.iconv(file_contents)
end

How to select option in drop down using Capybara

Unfortunately, the most popular answer did not work for me entirely. I had to add .select_option to end of the statement

select("option_name_here", from: "organizationSelect").select_option

without the select_option, no select was being performed

How to update Ruby Version 2.0.0 to the latest version in Mac OSX Yosemite?

Simplest way is definitely to enter the following command in the terminal:

sudo gem update --system

You can add the flag --no-document if you do not want to download the documentation. Here is sample output after running the command:

sudo gem update --system
Password:
Updating rubygems-update
Fetching: rubygems-update-2.6.8.gem (100%)
Successfully installed rubygems-update-2.6.8
Parsing documentation for rubygems-update-2.6.8
Installing ri documentation for rubygems-update-2.6.8
Installing darkfish documentation for rubygems-update-2.6.8
Installing RubyGems 2.6.8
RubyGems 2.6.8 installed
Parsing documentation for rubygems-2.6.8
Installing ri documentation for rubygems-2.6.8

------------------------------------------------------------------------------

RubyGems installed the following executables:
    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/gem

Ruby Interactive (ri) documentation was installed. ri is kind of like man 
pages for ruby libraries. You may access it like this:
  ri Classname
  ri Classname.class_method
  ri Classname#instance_method

Can't install gems on OS X "El Capitan"

I don't like to install stuff with sudo. once you start with sudo you can't stop..

try giving permissions to the Gems directory.

sudo chown -R $(whoami) /Library/Ruby/Gems/2.0.0

How to upgrade rubygems

Or:

gem update `gem outdated | cut -d ' ' -f 1`

Rails formatting date

Try this:

created_at.strftime('%FT%T')

It's a time formatting function which provides you a way to present the string representation of the date. (http://ruby-doc.org/core-2.2.1/Time.html#method-i-strftime).

From APIdock:

%Y%m%d           => 20071119                  Calendar date (basic)
%F               => 2007-11-19                Calendar date (extended)
%Y-%m            => 2007-11                   Calendar date, reduced accuracy, specific month
%Y               => 2007                      Calendar date, reduced accuracy, specific year
%C               => 20                        Calendar date, reduced accuracy, specific century
%Y%j             => 2007323                   Ordinal date (basic)
%Y-%j            => 2007-323                  Ordinal date (extended)
%GW%V%u          => 2007W471                  Week date (basic)
%G-W%V-%u        => 2007-W47-1                Week date (extended)
%GW%V            => 2007W47                   Week date, reduced accuracy, specific week (basic)
%G-W%V           => 2007-W47                  Week date, reduced accuracy, specific week (extended)
%H%M%S           => 083748                    Local time (basic)
%T               => 08:37:48                  Local time (extended)
%H%M             => 0837                      Local time, reduced accuracy, specific minute (basic)
%H:%M            => 08:37                     Local time, reduced accuracy, specific minute (extended)
%H               => 08                        Local time, reduced accuracy, specific hour
%H%M%S,%L        => 083748,000                Local time with decimal fraction, comma as decimal sign (basic)
%T,%L            => 08:37:48,000              Local time with decimal fraction, comma as decimal sign (extended)
%H%M%S.%L        => 083748.000                Local time with decimal fraction, full stop as decimal sign (basic)
%T.%L            => 08:37:48.000              Local time with decimal fraction, full stop as decimal sign (extended)
%H%M%S%z         => 083748-0600               Local time and the difference from UTC (basic)
%T%:z            => 08:37:48-06:00            Local time and the difference from UTC (extended)
%Y%m%dT%H%M%S%z  => 20071119T083748-0600      Date and time of day for calendar date (basic)
%FT%T%:z         => 2007-11-19T08:37:48-06:00 Date and time of day for calendar date (extended)
%Y%jT%H%M%S%z    => 2007323T083748-0600       Date and time of day for ordinal date (basic)
%Y-%jT%T%:z      => 2007-323T08:37:48-06:00   Date and time of day for ordinal date (extended)
%GW%V%uT%H%M%S%z => 2007W471T083748-0600      Date and time of day for week date (basic)
%G-W%V-%uT%T%:z  => 2007-W47-1T08:37:48-06:00 Date and time of day for week date (extended)
%Y%m%dT%H%M      => 20071119T0837             Calendar date and local time (basic)
%FT%R            => 2007-11-19T08:37          Calendar date and local time (extended)
%Y%jT%H%MZ       => 2007323T0837Z             Ordinal date and UTC of day (basic)
%Y-%jT%RZ        => 2007-323T08:37Z           Ordinal date and UTC of day (extended)
%GW%V%uT%H%M%z   => 2007W471T0837-0600        Week date and local time and difference from UTC (basic)
%G-W%V-%uT%R%:z  => 2007-W47-1T08:37-06:00    Week date and local time and difference from UTC (extended)

How do I encode/decode HTML entities in Ruby?

<% str="<h1> Test </h1>" %>

result: &lt; h1 &gt; Test &lt; /h1 &gt;

<%= CGI.unescapeHTML(str).html_safe %>

Rails 4: before_filter vs. before_action

before_filter/before_action: means anything to be executed before any action executes.

Both are same. they are just alias for each other as their behavior is same.

Format the date using Ruby on Rails

Here's my go at answering this,

so first you will need to convert the timestamp to an actual Ruby Date/Time. If you receive it just as a string or int from facebook, you will need to do something like this:

my_date = Time.at(timestamp_from_facebook.to_i)

OK, so now assuming you already have your date object...

to_formatted_s is a handy Ruby function that turns dates into formatted strings.

Here are some examples of its usage:

time = Time.now                     # => Thu Jan 18 06:10:17 CST 2007    

time.to_formatted_s(:time)          # => "06:10"
time.to_s(:time)                    # => "06:10"    

time.to_formatted_s(:db)            # => "2007-01-18 06:10:17"
time.to_formatted_s(:number)        # => "20070118061017"
time.to_formatted_s(:short)         # => "18 Jan 06:10"
time.to_formatted_s(:long)          # => "January 18, 2007 06:10"
time.to_formatted_s(:long_ordinal)  # => "January 18th, 2007 06:10"
time.to_formatted_s(:rfc822)        # => "Thu, 18 Jan 2007 06:10:17 -0600"

As you can see: :db, :number, :short ... are custom date formats.

To add your own custom format, you can create this file: config/initializers/time_formats.rb and add your own formats there, for example here's one:

Date::DATE_FORMATS[:month_day_comma_year] = "%B %e, %Y" # January 28, 2015

Where :month_day_comma_year is your format's name (you can change this to anything you want), and where %B %e, %Y is unix date format.

Here's a quick cheatsheet on unix date syntax, so you can quickly setup your custom format:

From http://linux.die.net/man/3/strftime    

  %a - The abbreviated weekday name (``Sun'')
  %A - The  full  weekday  name (``Sunday'')
  %b - The abbreviated month name (``Jan'')
  %B - The  full  month  name (``January'')
  %c - The preferred local date and time representation
  %d - Day of the month (01..31)
  %e - Day of the month without leading 0 (1..31) 
  %g - Year in YY (00-99)
  %H - Hour of the day, 24-hour clock (00..23)
  %I - Hour of the day, 12-hour clock (01..12)
  %j - Day of the year (001..366)
  %m - Month of the year (01..12)
  %M - Minute of the hour (00..59)
  %p - Meridian indicator (``AM''  or  ``PM'')
  %S - Second of the minute (00..60)
  %U - Week  number  of the current year,
          starting with the first Sunday as the first
          day of the first week (00..53)
  %W - Week  number  of the current year,
          starting with the first Monday as the first
          day of the first week (00..53)
  %w - Day of the week (Sunday is 0, 0..6)
  %x - Preferred representation for the date alone, no time
  %X - Preferred representation for the time alone, no date
  %y - Year without a century (00..99)
  %Y - Year with century
  %Z - Time zone name
  %% - Literal ``%'' character    

   t = Time.now
   t.strftime("Printed on %m/%d/%Y")   #=> "Printed on 04/09/2003"
   t.strftime("at %I:%M%p")            #=> "at 08:56AM"

Hope this helped you. I've also made a github gist of this little guide, in case anyone prefers.

What is Ruby's double-colon `::`?

Ruby on rails uses :: for namespace resolution.

class User < ActiveRecord::Base

  VIDEOS_COUNT = 10
  Languages = { "English" => "en", "Spanish" => "es", "Mandarin Chinese" => "cn"}

end

To use it :

User::VIDEOS_COUNT
User::Languages
User::Languages.values_at("Spanish") => "en"

Also, other usage is : When using nested routes

OmniauthCallbacksController is defined under users.

And routed as:

devise_for :users, controllers: {omniauth_callbacks: "users/omniauth_callbacks"}


class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController

end

Ruby: kind_of? vs. instance_of? vs. is_a?

I also wouldn't call two many (is_a? and kind_of? are aliases of the same method), but if you want to see more possibilities, turn your attention to #class method:

A = Class.new
B = Class.new A

a, b = A.new, B.new
b.class < A # true - means that b.class is a subclass of A
a.class < B # false - means that a.class is not a subclass of A
# Another possibility: Use #ancestors
b.class.ancestors.include? A # true - means that b.class has A among its ancestors
a.class.ancestors.include? B # false - means that B is not an ancestor of a.class

Ruby array to string conversion

I'll join the fun with:

['12','34','35','231'].join(', ')

EDIT:

"'#{['12','34','35','231'].join("', '")}'"

Some string interpolation to add the first and last single quote :P

What is the "right" way to iterate through an array in Ruby?

Trying to do the same thing consistently with arrays and hashes might just be a code smell, but, at the risk of my being branded as a codorous half-monkey-patcher, if you're looking for consistent behaviour, would this do the trick?:

class Hash
    def each_pairwise
        self.each { | x, y |
            yield [x, y]
        }
    end
end

class Array
    def each_pairwise
        self.each_with_index { | x, y |
            yield [y, x]
        }
    end
end

["a","b","c"].each_pairwise { |x,y|
    puts "#{x} => #{y}"
}

{"a" => "Aardvark","b" => "Bogle","c" => "Catastrophe"}.each_pairwise { |x,y|
    puts "#{x} => #{y}"
}

Ruby: Calling class method from instance

Using self.class.blah is NOT the same as using ClassName.blah when it comes to inheritance.

class Truck
  def self.default_make
    "mac"
  end

  def make1
    self.class.default_make
  end

  def make2
    Truck.default_make
  end
end


class BigTruck < Truck
  def self.default_make
    "bigmac"
  end
end

ruby-1.9.3-p0 :021 > b=BigTruck.new
 => #<BigTruck:0x0000000307f348> 
ruby-1.9.3-p0 :022 > b.make1
 => "bigmac" 
ruby-1.9.3-p0 :023 > b.make2
 => "mac" 

Add image to layout in ruby on rails

It's working for me:

<%= image_tag( root_url + "images/rss.jpg", size: "50x50", :alt => "rss feed") -%>

What does the question mark operator mean in Ruby?

It may be worth pointing out that ?s are only allowed in method names, not variables. In the process of learning Ruby, I assumed that ? designated a boolean return type so I tried adding them to flag variables, leading to errors. This led to me erroneously believing for a while that there was some special syntax involving ?s.

Relevant: Why can't a variable name end with `?` while a method name can?

How to add to an existing hash in Ruby

hash = { a: 'a', b: 'b' }
 => {:a=>"a", :b=>"b"}
hash.merge({ c: 'c', d: 'd' })
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"} 

Returns the merged value.

hash
 => {:a=>"a", :b=>"b"} 

But doesn't modify the caller object

hash = hash.merge({ c: 'c', d: 'd' })
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"} 
hash
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"} 

Reassignment does the trick.

Removing elements from array Ruby

You may do:

a= [1,1,1,2,2,3]
delete_list = [1,3]
delete_list.each do |del|
    a.delete_at(a.index(del))
end

result : [1, 1, 2, 2]

Installing RubyGems in Windows

I use scoop as command-liner installer for Windows... scoop rocks!
The quick answer (use PowerShell):

PS C:\Users\myuser> scoop install ruby

Longer answer:

Just searching for ruby:

PS C:\Users\myuser> scoop search ruby
'main' bucket:
    jruby (9.2.7.0)
    ruby (2.6.3-1)

'versions' bucket:
    ruby19 (1.9.3-p551)
    ruby24 (2.4.6-1)
    ruby25 (2.5.5-1)

Check the installation info :

PS C:\Users\myuser> scoop info ruby
Name: ruby
Version: 2.6.3-1
Website: https://rubyinstaller.org
Manifest:
  C:\Users\myuser\scoop\buckets\main\bucket\ruby.json
Installed: No
Environment: (simulated)
  GEM_HOME=C:\Users\myuser\scoop\apps\ruby\current\gems
  GEM_PATH=C:\Users\myuser\scoop\apps\ruby\current\gems
  PATH=%PATH%;C:\Users\myuser\scoop\apps\ruby\current\bin
  PATH=%PATH%;C:\Users\myuser\scoop\apps\ruby\current\gems\bin

Output from installation:

PS C:\Users\myuser> scoop install ruby
Updating Scoop...
Updating 'extras' bucket...
Installing 'ruby' (2.6.3-1) [64bit]
rubyinstaller-2.6.3-1-x64.7z (10.3 MB) [============================= ... ===========] 100%
Checking hash of rubyinstaller-2.6.3-1-x64.7z ... ok.
Extracting rubyinstaller-2.6.3-1-x64.7z ... done.
Linking ~\scoop\apps\ruby\current => ~\scoop\apps\ruby\2.6.3-1
Persisting gems
Running post-install script...
Fetching rake-12.3.3.gem
Successfully installed rake-12.3.3
Parsing documentation for rake-12.3.3
Installing ri documentation for rake-12.3.3
Done installing documentation for rake after 1 seconds
1 gem installed
'ruby' (2.6.3-1) was installed successfully!
Notes
-----
Install MSYS2 via 'scoop install msys2' and then run 'ridk install' to install the toolchain!
'ruby' suggests installing 'msys2'.
PS C:\Users\myuser>

Find value in an array

Like this?

a = [ "a", "b", "c", "d", "e" ]
a[2] +  a[0] + a[1]    #=> "cab"
a[6]                   #=> nil
a[1, 2]                #=> [ "b", "c" ]
a[1..3]                #=> [ "b", "c", "d" ]
a[4..7]                #=> [ "e" ]
a[6..10]               #=> nil
a[-3, 3]               #=> [ "c", "d", "e" ]
# special cases
a[5]                   #=> nil
a[5, 1]                #=> []
a[5..10]               #=> []

or like this?

a = [ "a", "b", "c" ]
a.index("b")   #=> 1
a.index("z")   #=> nil

See the manual.

What is the best method of handling currency/money?

Just a little update and a cohesion of all the answers for some aspiring juniors/beginners in RoR development that will surely come here for some explanations.

Working with money

Use :decimal to store money in the DB, as @molf suggested (and what my company uses as a golden standard when working with money).

# precision is the total number of digits
# scale is the number of digits to the right of the decimal point
add_column :items, :price, :decimal, precision: 8, scale: 2

Few points:

  • :decimal is going to be used as BigDecimal which solves a lot of issues.

  • precision and scale should be adjusted, depending on what you are representing

    • If you work with receiving and sending payments, precision: 8 and scale: 2 gives you 999,999.99 as the highest amount, which is fine in 90% of cases.

    • If you need to represent the value of a property or a rare car, you should use a higher precision.

    • If you work with coordinates (longitude and latitude), you will surely need a higher scale.

How to generate a migration

To generate the migration with the above content, run in terminal:

bin/rails g migration AddPriceToItems price:decimal{8-2}

or

bin/rails g migration AddPriceToItems 'price:decimal{5,2}'

as explained in this blog post.

Currency formatting

KISS the extra libraries goodbye and use built-in helpers. Use number_to_currency as @molf and @facundofarias suggested.

To play with number_to_currency helper in Rails console, send a call to the ActiveSupport's NumberHelper class in order to access the helper.

For example:

ActiveSupport::NumberHelper.number_to_currency(2_500_000.61, unit: '€', precision: 2, separator: ',', delimiter: '', format: "%n%u")

gives the following output

2500000,61€

Check the other options of number_to_currency helper.

Where to put it

You can put it in an application helper and use it inside views for any amount.

module ApplicationHelper    
  def format_currency(amount)
    number_to_currency(amount, unit: '€', precision: 2, separator: ',', delimiter: '', format: "%n%u")
  end
end

Or you can put it in the Item model as an instance method, and call it where you need to format the price (in views or helpers).

class Item < ActiveRecord::Base
  def format_price
    number_to_currency(price, unit: '€', precision: 2, separator: ',', delimiter: '', format: "%n%u")
  end
end

And, an example how I use the number_to_currency inside a contrroler (notice the negative_format option, used to represent refunds)

def refund_information
  amount_formatted = 
    ActionController::Base.helpers.number_to_currency(@refund.amount, negative_format: '(%u%n)')
  {
    # ...
    amount_formatted: amount_formatted,
    # ...
  }
end

TypeError: no implicit conversion of Symbol into Integer

myHash.each{|item|..} is returning you array object for item iterative variable like the following :--

[:company_name, "MyCompany"]
[:street, "Mainstreet"]
[:postcode, "1234"]
[:city, "MyCity"]
[:free_seats, "3"]

You should do this:--

def format
  output = Hash.new
  myHash.each do |k, v|
    output[k] = cleanup(v)
  end
  output
end

What is the difference between <%, <%=, <%# and -%> in ERB in Rails?

  • <% %> : Executes the ruby code
  • <%= %> : Prints into Erb file. Or browser
  • <% -%> : Avoids line break after expression.
  • <%# %> : ERB comment

Iterate through every file in one directory

The find library is designed for this task specifically: https://ruby-doc.org/stdlib-2.5.1/libdoc/find/rdoc/Find.html

require 'find'
Find.find(path) do |file|
  # process
end

This is a standard ruby library, so it should be available

Syntax for a for loop in ruby

['foo', 'bar', 'baz'].each_with_index {|j, i| puts "#{i} #{j}"}

How do I convert a String object into a Hash object?

For different string, you can do it without using dangerous eval method:

hash_as_string = "{\"0\"=>{\"answer\"=>\"1\", \"value\"=>\"No\"}, \"1\"=>{\"answer\"=>\"2\", \"value\"=>\"Yes\"}, \"2\"=>{\"answer\"=>\"3\", \"value\"=>\"No\"}, \"3\"=>{\"answer\"=>\"4\", \"value\"=>\"1\"}, \"4\"=>{\"value\"=>\"2\"}, \"5\"=>{\"value\"=>\"3\"}, \"6\"=>{\"value\"=>\"4\"}}"
JSON.parse hash_as_string.gsub('=>', ':')

Rails Object to hash

Swanand's answer is great.

if you are using FactoryGirl, you can use its build method to generate the attribute hash without the key id. e.g.

build(:post).attributes

Uploading a file in Rails

There is a nice gem especially for uploading files : carrierwave. If the wiki does not help , there is a nice RailsCast about the best way to use it . Summarizing , there is a field type file in Rails forms , which invokes the file upload dialog. You can use it , but the 'magic' is done by carrierwave gem .

I don't know what do you mean with "how to write to a file" , but I hope this is a nice start.

EOFError: end of file reached issue with Net::HTTP

If the URL is using https instead of http, you need to add the following line:

parsed_url = URI.parse(url)
http = Net::HTTP.new(parsed_url.host, parsed_url.port)
http.use_ssl = true

Note the additional http.use_ssl = true.

And the more appropriate code which would handle both http and https will be similar to the following one.

url = URI.parse(domain)
req = Net::HTTP::Post.new(url.request_uri)
req.set_form_data({'name'=>'Sur Max', 'email'=>'[email protected]'})
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = (url.scheme == "https")
response = http.request(req)

See more in my blog: EOFError: end of file reached issue when post a form with Net::HTTP.

Determining type of an object in ruby

variable_name.class

Here variable name is "a" a.class

SSL Error When installing rubygems, Unable to pull data from 'https://rubygems.org/

If you want to use the non-SSL source, try removing the HTTPS source first, and then adding the HTTP one:

sudo gem sources -r https://rubygems.org
sudo gem sources -a http://rubygems.org  

UPDATE:

As mpapis states, this should be used only as a temporary workaround. There could be some security concerns if you're accessing RubyGems through the non-SSL source.

Once the workaround is not needed anymore, you should restore the SSL-source:

sudo gem sources -r http://rubygems.org
sudo gem sources -a https://rubygems.org

How do I get ruby to print a full backtrace instead of a truncated one?

I was getting these errors when trying to load my test environment (via rake test or autotest) and the IRB suggestions didn't help. I ended up wrapping my entire test/test_helper.rb in a begin/rescue block and that fixed things up.

begin
  class ActiveSupport::TestCase
    #awesome stuff
  end
rescue => e
  puts e.backtrace
end

How to redirect to a 404 in Rails?

You could also use the render file:

render file: "#{Rails.root}/public/404.html", layout: false, status: 404

Where you can choose to use the layout or not.

Another option is to use the Exceptions to control it:

raise ActiveRecord::RecordNotFound, "Record not found."

Checking if a variable is an integer

If you want to know whether an object is an Integer or something which can meaningfully be converted to an Integer (NOT including things like "hello", which to_i will convert to 0):

result = Integer(obj) rescue false

Rails DateTime.now without Time

What about Date.today.to_time?

How to implement Enums in Ruby?

Try the inum. https://github.com/alfa-jpn/inum

class Color < Inum::Base
  define :RED
  define :GREEN
  define :BLUE
end
Color::RED 
Color.parse('blue') # => Color::BLUE
Color.parse(2)      # => Color::GREEN

see more https://github.com/alfa-jpn/inum#usage

Failed to build gem native extension (installing Compass)

Try this, then try to install compass again

apt-get install ruby-dev

Check whether a variable is a string in Ruby

You can do:

foo.instance_of?(String)

And the more general:

foo.kind_of?(String)

Ruby on Rails: how to render a string as HTML?

If you're on rails which utilizes Erubis — the coolest way to do it is

<%== @str >

Note the double equal sign. See related question on SO for more info.

How to call shell commands from Ruby

My favourite is Open3

  require "open3"

  Open3.popen3('nroff -man') { |stdin, stdout, stderr| ... }

How to get UTC timestamp in Ruby?

The default formatting is not very useful, in my opinion. I prefer ISO8601 as it's sortable, relatively compact and widely recognized:

>> require 'time'
=> true
>> Time.now.utc.iso8601
=> "2011-07-28T23:14:04Z"

Dynamic constant assignment

Because constants in Ruby aren't meant to be changed, Ruby discourages you from assigning to them in parts of code which might get executed more than once, such as inside methods.

Under normal circumstances, you should define the constant inside the class itself:

class MyClass
  MY_CONSTANT = "foo"
end

MyClass::MY_CONSTANT #=> "foo"

If for some reason though you really do need to define a constant inside a method (perhaps for some type of metaprogramming), you can use const_set:

class MyClass
  def my_method
    self.class.const_set(:MY_CONSTANT, "foo")
  end
end

MyClass::MY_CONSTANT
#=> NameError: uninitialized constant MyClass::MY_CONSTANT

MyClass.new.my_method
MyClass::MY_CONSTANT #=> "foo"

Again though, const_set isn't something you should really have to resort to under normal circumstances. If you're not sure whether you really want to be assigning to constants this way, you may want to consider one of the following alternatives:

Class variables

Class variables behave like constants in many ways. They are properties on a class, and they are accessible in subclasses of the class they are defined on.

The difference is that class variables are meant to be modifiable, and can therefore be assigned to inside methods with no issue.

class MyClass
  def self.my_class_variable
    @@my_class_variable
  end
  def my_method
    @@my_class_variable = "foo"
  end
end
class SubClass < MyClass
end

MyClass.my_class_variable
#=> NameError: uninitialized class variable @@my_class_variable in MyClass
SubClass.my_class_variable
#=> NameError: uninitialized class variable @@my_class_variable in MyClass

MyClass.new.my_method
MyClass.my_class_variable #=> "foo"
SubClass.my_class_variable #=> "foo"

Class attributes

Class attributes are a sort of "instance variable on a class". They behave a bit like class variables, except that their values are not shared with subclasses.

class MyClass
  class << self
    attr_accessor :my_class_attribute
  end
  def my_method
    self.class.my_class_attribute = "blah"
  end
end
class SubClass < MyClass
end

MyClass.my_class_attribute #=> nil
SubClass.my_class_attribute #=> nil

MyClass.new.my_method
MyClass.my_class_attribute #=> "blah"
SubClass.my_class_attribute #=> nil

SubClass.new.my_method
SubClass.my_class_attribute #=> "blah"

Instance variables

And just for completeness I should probably mention: if you need to assign a value which can only be determined after your class has been instantiated, there's a good chance you might actually be looking for a plain old instance variable.

class MyClass
  attr_accessor :instance_variable
  def my_method
    @instance_variable = "blah"
  end
end

my_object = MyClass.new
my_object.instance_variable #=> nil
my_object.my_method
my_object.instance_variable #=> "blah"

MyClass.new.instance_variable #=> nil

How to check if a Ruby object is a Boolean

There is no Boolean class in Ruby, the only way to check is to do what you're doing (comparing the object against true and false or the class of the object against TrueClass and FalseClass). Can't think of why you would need this functionality though, can you explain? :)

If you really need this functionality however, you can hack it in:

module Boolean; end
class TrueClass; include Boolean; end
class FalseClass; include Boolean; end

true.is_a?(Boolean) #=> true
false.is_a?(Boolean) #=> true

Which Ruby version am I really running?

On your terminal, try running:

which -a ruby

This will output all the installed Ruby versions (via RVM, or otherwise) on your system in your PATH. If 1.8.7 is your system Ruby version, you can uninstall the system Ruby using:

sudo apt-get purge ruby

Once you have made sure you have Ruby installed via RVM alone, in your login shell you can type:

rvm --default use 2.0.0

You don't need to do this if you have only one Ruby version installed.

If you still face issues with any system Ruby files, try running:

dpkg-query -l '*ruby*'

This will output a bunch of Ruby-related files and packages which are, or were, installed on your system at the system level. Check the status of each to find if any of them is native and is causing issues.

gem install: Failed to build gem native extension (can't find header files)

You need following packages instaled:

  • ruby-dev

  • gcc

  • libffi-dev

  • make

Here's the command for debian distro:

 sudo apt install gcc ruby-dev rubygems libgmp-dev libgmp3-dev make 

How do I dump an object's fields to the console?

p object

Ruby doc for p.

p(*args) public

For each object, directly writes obj.inspect followed by a newline to the program’s standard output.

How to Uninstall RVM?

It’s easy; just do the following:

rvm implode

or

rm -rf ~/.rvm

And don’t forget to remove the script calls in the following files:

  • ~/.bashrc
  • ~/.bash_profile
  • ~/.profile

And maybe others depending on whatever shell you’re using.

Is There a Better Way of Checking Nil or Length == 0 of a String in Ruby?

variable.blank? will do it. It returns true if the string is empty or if the string is nil.

getaddrinfo: nodename nor servname provided, or not known

To avoid this problem, we can bind to 127.0.0.1 instead of localhost:

bin/rails server -b 127.0.0.1

Ruby: Easiest Way to Filter Hash Keys?

This is a one line to solve the complete original question:

params.select { |k,_| k[/choice/]}.values.join('\t')

But most the solutions above are solving a case where you need to know the keys ahead of time, using slice or simple regexp.

Here is another approach that works for simple and more complex use cases, that is swappable at runtime

data = {}
matcher = ->(key,value) { COMPLEX LOGIC HERE }
data.select(&matcher)

Now not only this allows for more complex logic on matching the keys or the values, but it is also easier to test, and you can swap the matching logic at runtime.

Ex to solve the original issue:

def some_method(hash, matcher) 
  hash.select(&matcher).values.join('\t')
end

params = { :irrelevant => "A String",
           :choice1 => "Oh look, another one",
           :choice2 => "Even more strings",
           :choice3 => "But wait",
           :irrelevant2 => "The last string" }

some_method(params, ->(k,_) { k[/choice/]}) # => "Oh look, another one\\tEven more strings\\tBut wait"
some_method(params, ->(_,v) { v[/string/]}) # => "Even more strings\\tThe last string"

How do I specify local .gem files in my Gemfile?

Seems bundler can't use .gem files out of the box. Pointing the :path to a directory containing .gem files doesn't work. Some people suggested to setup a local gem server (geminabox, stickler) for that purpose.

However, what I found to be much simpler is to use a local gem "server" from file system: Just put your .gem files in a local directory, then use "gem generate_index" to make it a Gem repository

mkdir repo
mkdir repo/gems
cp *.gem repo/gems
cd repo
gem generate_index

Finally point bundler to this location by adding the following line to your Gemfile

source "file://path/to/repo"

If you update the gems in the repository, make sure to regenerate the index.

unable to install pg gem

I had to do this on CentOS 5.8. Running bundle install kept causing issues since I couldn't force it to use a particular PG version.

I can't yum erase postgresql postgresql-devel either, because of dependency issues (it would remove php, http etc)

The solution? Mess $PATH temporarily to give preference to the update pgsql instead of the default one:

export PATH=/usr/pgsql-9.2/bin:$PATH
bundle install

Basically, with the above commands, it will look at /usr/pgsql-9.2/bin/pg_config before the one in /usr/bin/pg_config

How to install a specific version of a ruby gem?

Linux

To install different version of ruby, check the latest version of package using apt as below:

$ apt-cache madison ruby
      ruby |    1:1.9.3 | http://ftp.uk.debian.org/debian/ wheezy/main amd64 Packages
      ruby |        4.5 | http://ftp.uk.debian.org/debian/ squeeze/main amd64 Packages

Then install it:

$ sudo apt-get install ruby=1:1.9.3

To check what's the current version, run:

$ gem --version # Check for the current user.
$ sudo gem --version # Check globally.

If the version is still old, you may try to switch the version to new by using ruby version manager (rvm) by:

rvm 1.9.3

Note: You may prefix it by sudo if rvm was installed globally. Or run /usr/local/rvm/scripts/rvm if your command rvm is not in your global PATH. If rvm installation process failed, see the troubleshooting section.


Troubleshooting:

  • If you still have the old version, you may try to install rvm (ruby version manager) via:

    sudo apt-get install curl # Install curl first
    curl -sSL https://get.rvm.io | bash -s stable --ruby # Install only for the user.
    #or:# curl -sSL https://get.rvm.io | sudo bash -s stable --ruby # Install globally. 
    

    then if installed locally (only for current user), load rvm via:

    source /usr/local/rvm/scripts/rvm; rvm 1.9.3
    

    if globally (for all users), then:

    sudo bash -c "source /usr/local/rvm/scripts/rvm; rvm 1.9.3"
    
  • if you still having problem with the new ruby version, try to install it by rvm via:

    source /usr/local/rvm/scripts/rvm && rvm install ruby-1.9.3 # Locally.
    sudo bash -c "source /usr/local/rvm/scripts/rvm && rvm install ruby-1.9.3" # Globally.
    
  • if you'd like to install some gems globally and you have rvm already installed, you may try:

    rvmsudo gem install [gemname]
    

    instead of:

      gem install [gemname] # or:
      sudo gem install [gemname]
    

Note: It's prefered to NOT use sudo to work with RVM gems. When you do sudo you are running commands as root, another user in another shell and hence all of the setup that RVM has done for you is ignored while the command runs under sudo (such things as GEM_HOME, etc...). So to reiterate, as soon as you 'sudo' you are running as the root system user which will clear out your environment as well as any files it creates are not able to be modified by your user and will result in strange things happening.

Breaking up long strings on multiple lines in Ruby without stripping newlines

I modified Zack's answer since I wanted spaces and interpolation but not newlines and used:

%W[
  It's a nice day "#{name}"
  for a walk!
].join(' ')

where name = 'fred' this produces It's a nice day "fred" for a walk!

How can I remove the string "\n" from within a Ruby string?

When you want to remove a string, rather than replace it you can use String#delete (or its mutator equivalent String#delete!), e.g.:

x = "foo\nfoo"
x.delete!("\n")

x now equals "foofoo"

In this specific case String#delete is more readable than gsub since you are not actually replacing the string with anything.

Rails update_attributes without save?

You can use assign_attributes or attributes= (they're the same)

Update methods cheat sheet (for Rails 6):

  • update = assign_attributes + save
  • attributes= = alias of assign_attributes
  • update_attributes = deprecated, alias of update

Source:
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/persistence.rb
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/attribute_assignment.rb

Another cheat sheet:
http://www.davidverhasselt.com/set-attributes-in-activerecord/#cheat-sheet

What does the "map" method do in Ruby?

The map method takes an enumerable object and a block, and runs the block for each element, outputting each returned value from the block (the original object is unchanged unless you use map!):

[1, 2, 3].map { |n| n * n } #=> [1, 4, 9]

Array and Range are enumerable types. map with a block returns an Array. map! mutates the original array.

Where is this helpful, and what is the difference between map! and each? Here is an example:

names = ['danil', 'edmund']

# here we map one array to another, convert each element by some rule
names.map! {|name| name.capitalize } # now names contains ['Danil', 'Edmund']

names.each { |name| puts name + ' is a programmer' } # here we just do something with each element

The output:

Danil is a programmer
Edmund is a programmer

What is the easiest way to push an element to the beginning of the array?

You can also use array concatenation:

a = [2, 3]
[1] + a
=> [1, 2, 3]

This creates a new array and doesn't modify the original.

Create a new Ruby on Rails application using MySQL instead of SQLite

$ rails --help 

is always your best friend

usage:

$ rails new APP_PATH[options]

also note that options should be given after the application name

rails and mysql

$ rails new project_name -d mysql

rails and postgresql

$ rails new project_name -d postgresql

rbenv not changing ruby version

Linux / Ubuntu Users Step 1:

$ rbenv versions
  system
  2.6.0
* 2.7.0 (set by /home/User/Documents/sample-app/.ruby-version) #Yours will be different
  2.7.2

Step 2:

$ nano /home/User/Documents/sample-app/.ruby-version

Step 3:

$ ruby -v
ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-linux]

What is the best way to convert an array to a hash in Ruby

Edit: Saw the responses posted while I was writing, Hash[a.flatten] seems the way to go. Must have missed that bit in the documentation when I was thinking through the response. Thought the solutions that I've written can be used as alternatives if required.

The second form is simpler:

a = [[:apple, 1], [:banana, 2]]
h = a.inject({}) { |r, i| r[i.first] = i.last; r }

a = array, h = hash, r = return-value hash (the one we accumulate in), i = item in the array

The neatest way that I can think of doing the first form is something like this:

a = [:apple, 1, :banana, 2]
h = {}
a.each_slice(2) { |i| h[i.first] = i.last }

Fastest way to check if a string matches a regexp in ruby?

Depending on how complicated your regular expression is, you could possibly just use simple string slicing. I'm not sure about the practicality of this for your application or whether or not it would actually offer any speed improvements.

'testsentence'['stsen']
=> 'stsen' # evaluates to true
'testsentence'['koala']
=> nil # evaluates to false

Ruby combining an array into one string

Use the Array#join method (the argument to join is what to insert between the strings - in this case a space):

@arr.join(" ")

Why use Ruby's attr_accessor, attr_reader and attr_writer?

Not all attributes of an object are meant to be directly set from outside the class. Having writers for all your instance variables is generally a sign of weak encapsulation and a warning that you're introducing too much coupling between your classes.

As a practical example: I wrote a design program where you put items inside containers. The item had attr_reader :container, but it didn't make sense to offer a writer, since the only time the item's container should change is when it's placed in a new one, which also requires positioning information.

Is there a "do ... while" loop in Ruby?

ppl = []
while (input=gets.chomp)
 if !input.empty?
  ppl << input
 else
 p ppl; puts "Goodbye"; break
 end
end

How to convert a string or integer to binary in Ruby?

I am almost a decade late but if someone still come here and want to find the code without using inbuilt function like to_S then I might be helpful.

find the binary

def find_binary(number)
  binary = []  
  until(number == 0)
    binary << number%2
    number = number/2
  end
  puts binary.reverse.join
end

How to initialize an array in one step using Ruby?

You can simply do this with %w notation in ruby arrays.

array = %w(1 2 3)

It will add the array values 1,2,3 to the arrayand print out the output as ["1", "2", "3"]

Replace words in a string - Ruby

If you're dealing with natural language text and need to replace a word, not just part of a string, you have to add a pinch of regular expressions to your gsub as a plain text substitution can lead to disastrous results:

'mislocated cat, vindicating'.gsub('cat', 'dog')
=> "mislodoged dog, vindidoging"

Regular expressions have word boundaries, such as \b which matches start or end of a word. Thus,

'mislocated cat, vindicating'.gsub(/\bcat\b/, 'dog')
=> "mislocated dog, vindicating"

In Ruby, unlike some other languages like Javascript, word boundaries are UTF-8-compatible, so you can use it for languages with non-Latin or extended Latin alphabets:

'???? ? ??????, ??? ??????'.gsub(/\b????\b/, '?????')
=> "????? ? ??????, ??? ??????"

Ruby - test for array

Also consider using Array(). From the Ruby Community Style Guide:

Use Array() instead of explicit Array check or [*var], when dealing with a variable you want to treat as an Array, but you're not certain it's an array.

# bad
paths = [paths] unless paths.is_a? Array
paths.each { |path| do_something(path) }

# bad (always creates a new Array instance)
[*paths].each { |path| do_something(path) }

# good (and a bit more readable)
Array(paths).each { |path| do_something(path) }

Difference between attr_accessor and attr_accessible

Many people on this thread and on google explain very well that attr_accessible specifies a whitelist of attributes that are allowed to be updated in bulk (all the attributes of an object model together at the same time) This is mainly (and only) to protect your application from "Mass assignment" pirate exploit.

This is explained here on the official Rails doc : Mass Assignment

attr_accessor is a ruby code to (quickly) create setter and getter methods in a Class. That's all.

Now, what is missing as an explanation is that when you create somehow a link between a (Rails) model with a database table, you NEVER, NEVER, NEVER need attr_accessor in your model to create setters and getters in order to be able to modify your table's records.

This is because your model inherits all methods from the ActiveRecord::Base Class, which already defines basic CRUD accessors (Create, Read, Update, Delete) for you. This is explained on the offical doc here Rails Model and here Overwriting default accessor (scroll down to the chapter "Overwrite default accessor")

Say for instance that: we have a database table called "users" that contains three columns "firstname", "lastname" and "role" :

SQL instructions :

CREATE TABLE users (
  firstname string,
  lastname string
  role string
);

I assumed that you set the option config.active_record.whitelist_attributes = true in your config/environment/production.rb to protect your application from Mass assignment exploit. This is explained here : Mass Assignment

Your Rails model will perfectly work with the Model here below :

class User < ActiveRecord::Base

end

However you will need to update each attribute of user separately in your controller for your form's View to work :

def update
    @user = User.find_by_id(params[:id])
    @user.firstname = params[:user][:firstname]
    @user.lastname = params[:user][:lastname]

    if @user.save
        # Use of I18 internationalization t method for the flash message
        flash[:success] = t('activerecord.successful.messages.updated', :model => User.model_name.human)
    end

    respond_with(@user)
end

Now to ease your life, you don't want to make a complicated controller for your User model. So you will use the attr_accessible special method in your Class model :

class User < ActiveRecord::Base

  attr_accessible :firstname, :lastname

end

So you can use the "highway" (mass assignment) to update :

def update
    @user = User.find_by_id(params[:id])

    if @user.update_attributes(params[:user])
        # Use of I18 internationlization t method for the flash message
        flash[:success] = t('activerecord.successful.messages.updated', :model => User.model_name.human)
    end

    respond_with(@user)
end

You didn't add the "role" attributes to the attr_accessible list because you don't let your users set their role by themselves (like admin). You do this yourself on another special admin View.

Though your user view doesn't show a "role" field, a pirate could easily send a HTTP POST request that include "role" in the params hash. The missing "role" attribute on the attr_accessible is to protect your application from that.

You can still modify your user.role attribute on its own like below, but not with all attributes together.

@user.role = DEFAULT_ROLE

Why the hell would you use the attr_accessor?

Well, this would be in the case that your user-form shows a field that doesn't exist in your users table as a column.

For instance, say your user view shows a "please-tell-the-admin-that-I'm-in-here" field. You don't want to store this info in your table. You just want that Rails send you an e-mail warning you that one "crazy" ;-) user has subscribed.

To be able to make use of this info you need to store it temporarily somewhere. What more easy than recover it in a user.peekaboo attribute ?

So you add this field to your model :

class User < ActiveRecord::Base

  attr_accessible :firstname, :lastname
  attr_accessor :peekaboo

end

So you will be able to make an educated use of the user.peekaboo attribute somewhere in your controller to send an e-mail or do whatever you want.

ActiveRecord will not save the "peekaboo" attribute in your table when you do a user.save because she don't see any column matching this name in her model.

Best way to pretty print a hash

Another solution which works better for me than pp or awesome_print:

require 'pry' # must install the gem... but you ALWAYS want pry installed anyways
Pry::ColorPrinter.pp(obj)

How do I get unique elements in this array?

Have you looked at this page?

http://www.mongodb.org/display/DOCS/Aggregation#Aggregation-Distinct

That might save you some time?

eg db.addresses.distinct("zip-code");

Uninstall old versions of Ruby gems

You might need to set GEM_HOME for the cleanup to work. You can check what paths exist for gemfiles by running:

gem env

Take note of the GEM PATHS section.

In my case, for example, with gems installed in my user home:

export GEM_HOME="~/.gem/ruby/2.4.0"
gem cleanup

String "true" and "false" to boolean

ActiveRecord provides a clean way of doing this.

def is_true?(string)
  ActiveRecord::ConnectionAdapters::Column::TRUE_VALUES.include?(string)
end

ActiveRecord::ConnectionAdapters::Column::TRUE_VALUES has all of the obvious representations of True values as strings.

How to get a substring of text?

If you want a string, then the other answers are fine, but if what you're looking for is the first few letters as characters you can access them as a list:

your_text.chars.take(30)

How to sum array of numbers in Ruby?

ruby 1.8.7 way is the following:

array.inject(0, &:+) 

Ruby 2.0.0p0 IRB warning: "DL is deprecated, please use Fiddle"

I ran into this myself when I wanted to make a thor command under Windows.

To avoid having that message output everytime I ran my thor application I temporarily muted warnings while loading thor:

begin
  original_verbose = $VERBOSE
  $VERBOSE = nil
  require "thor"
ensure
  $VERBOSE = original_verbose
end

That saved me from having to edit third party source files.

Best way to convert strings to symbols in hash

Even more terse:

Hash[my_hash.map{|(k,v)| [k.to_sym,v]}]

How to check for file existence

Check out Pathname and in particular Pathname#exist?.

File and its FileTest module are perhaps simpler/more direct, but I find Pathname a nicer interface in general.

ssh: connect to host github.com port 22: Connection timed out

Changing the repo url from ssh to https is not very meaningful to me. As I prefer ssh over https because of some sort of extra benefits which I don't want to discard. Above answers are pretty good and accurate. If you face this problem in GitLab, please go to their official documentation page and change your config file like that.

Host gitlab.com
  Hostname altssh.gitlab.com
  User git
  Port 443
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/gitlab

Why do we need to use flatMap?

flatMap transform the items emitted by an Observable into new Observables, then flattens the emissions from those into a single Observable.

Check out the scenario below where get("posts") returns an Observable that is "flattened" by flatMap.

myObservable.map(e => get("posts")).subscribe(o => console.log(o));
// this would log Observable objects to console.  

myObservable.flatMap(e => get("posts")).subscribe(o => console.log(o));
// this would log posts to console.

Adding and reading from a Config file

  1. Add an Application Configuration File item to your project (Right -Click Project > Add item). This will create a file called app.config in your project.

  2. Edit the file by adding entries like <add key="keyname" value="someValue" /> within the <appSettings> tag.

  3. Add a reference to the System.Configuration dll, and reference the items in the config using code like ConfigurationManager.AppSettings["keyname"].

Python dictionary: Get list of values for list of keys

Try this:

mydict = {'one': 1, 'two': 2, 'three': 3}
mykeys = ['three', 'one'] # if there are many keys, use a set

[mydict[k] for k in mykeys]
=> [3, 1]

XOR operation with two strings in java

Assuming (!) the strings are of equal length, why not convert the strings to byte arrays and then XOR the bytes. The resultant byte arrays may be of different lengths too depending on your encoding (e.g. UTF8 will expand to different byte lengths for different characters).

You should be careful to specify the character encoding to ensure consistent/reliable string/byte conversion.

Turn a number into star rating display using jQuery and CSS

DEMO

You can do it with 2 images only. 1 blank stars, 1 filled stars.

Overlay filled image on the top of the other one. and convert rating number into percentage and use it as width of fillter image.

enter image description here

.containerdiv {
  border: 0;
  float: left;
  position: relative;
  width: 300px;
} 
.cornerimage {
  border: 0;
  position: absolute;
  top: 0;
  left: 0;
  overflow: hidden;
 } 
 img{
   max-width: 300px;
 }

QR Code encoding and decoding using zxing

So, for future reference for anybody who doesn't want to spend two days searching the internet to figure this out, when you encode byte arrays into QR Codes, you have to use the ISO-8859-1character set, not UTF-8.

Python 2.7.10 error "from urllib.request import urlopen" no module named request

Try using urllib2:

https://docs.python.org/2/library/urllib2.html

This line should work to replace urlopen:

from urllib2 import urlopen

Tested in Python 2.7 on Macbook Pro

Try posting a link to the git in question.

How to validate a form with multiple checkboxes to have atleast one checked

How about this:

$(document).ready(function() {
    $('#subscribeForm').submit(function() {
        var $fields = $(this).find('input[name="list"]:checked');
        if (!$fields.length) {
            alert('You must check at least one box!');
            return false; // The form will *not* submit
        }
    });
});

Is a Python list guaranteed to have its elements stay in the order they are inserted in?

You are confusing 'sets' and 'lists'. A set does not guarantee order, but lists do.

Sets are declared using curly brackets: {}. In contrast, lists are declared using square brackets: [].

mySet = {a, b, c, c}

Does not guarantee order, but list does:

myList = [a, b, c]

Common MySQL fields and their appropriate data types

I am doing about the same thing, and here's what I did.

I used separate tables for name, address, email, and numbers, each with a NameID column that is a foreign key on everything except the Name table, on which it is the primary clustered key. I used MainName and FirstName instead of LastName and FirstName to allow for business entries as well as personal entries, but you may not have a need for that.

The NameID column gets to be a smallint in all the tables because I'm fairly certain I won't make more than 32000 entries. Almost everything else is varchar(n) ranging from 20 to 200, depending on what you wanna store (Birthdays, comments, emails, really long names). That is really dependent on what kind of stuff you're storing.

The Numbers table is where I deviate from that. I set it up to have five columns labeled NameID, Phone#, CountryCode, Extension, and PhoneType. I already discussed NameID. Phone# is varchar(12) with a check constraint looking something like this: CHECK (Phone# like '[0-9][0-9][0-9]-[0-9][0-9][0-9]-[0-9][0-9][0-9][0-9]'). This ensures that only what I want makes it into the database and the data stays very consistent. The extension and country codes I called nullable smallints, but those could be varchar if you wanted to. PhoneType is varchar(20) and is not nullable.

Hope this helps!

How to change file encoding in NetBeans?

Yes, you can change the encoding of a specific file (or see what it has) with this Encoding Support plugin. With this plugin you will be able to handle the different encodings of your files without problems.

Now it is in version 1.4.0 for NetBeans 8.2 and I use it in Windows 10 several time ago.

The operation is very simple, in the status line you can see the encoding of the open file, and from there you can define its new encoding.

Encoding Support running on Windows 10

CSS Always On Top

Assuming that your markup looks like:

<div id="header" style="position: fixed;"></div>
<div id="content" style="position: relative;"></div>

Now both elements are positioned; in which case, the element at the bottom (in source order) will cover element above it (in source order).

Add a z-index on header; 1 should be sufficient.

Eclipse: Enable autocomplete / content assist

For anyone having this problem with newer versions of Eclipse, head over to Window->Preferences->Java->Editor->Content assist->Advanced and mark Java Proposals and Chain Template Proposals as active.

Integrity constraint violation: 1452 Cannot add or update a child row:

I had the same error, the problem was that I was trying to add role_id foreign to the users table, but role_id did not have a default value, so the DB did not allow me to insert the column because I already had some users and it didn't know how to add the column to them. Since I was in development I just used migrate:fresh, but if I was on production, I would probably set a default value to the role_id and not make it not constrained until I had the corresponding role on the DB.

Explaining Python's '__enter__' and '__exit__'

In addition to the above answers to exemplify invocation order, a simple run example

class myclass:
    def __init__(self):
        print("__init__")

    def __enter__(self): 
        print("__enter__")

    def __exit__(self, type, value, traceback):
        print("__exit__")

    def __del__(self):
        print("__del__")

with myclass(): 
    print("body")

Produces the output:

__init__
__enter__
body
__exit__
__del__

A reminder: when using the syntax with myclass() as mc, variable mc gets the value returned by __enter__(), in the above case None! For such use, need to define return value, such as:

def __enter__(self): 
    print('__enter__')
    return self

Initial size for the ArrayList

I faced with the similar issue, and just knowing the arrayList is a resizable-array implementation of the List interface, I also expect you can add element to any point, but at least have the option to define the initial size. Anyway, you can create an array first and convert that to a list like:

  int index = 5;
  int size = 10;

  Integer[] array = new Integer[size];
  array[index] = value;
  ...
  List<Integer> list = Arrays.asList(array);

or

  List<Integer> list = Arrays.asList(new Integer[size]);
  list.set(index, value);

Checking on a thread / remove from list

you need to call thread.isAlive()to find out if the thread is still running

Can anyone explain python's relative imports?

If you are going to call relative.py directly and i.e. if you really want to import from a top level module you have to explicitly add it to the sys.path list.
Here is how it should work:

# Add this line to the beginning of relative.py file
import sys
sys.path.append('..')

# Now you can do imports from one directory top cause it is in the sys.path
import parent

# And even like this:
from parent import Parent

If you think the above can cause some kind of inconsistency you can use this instead:

sys.path.append(sys.path[0] + "/..")

sys.path[0] refers to the path that the entry point was ran from.

How to ignore conflicts in rpm installs

The --force option will reinstall already installed packages or overwrite already installed files from other packages. You don't want this normally.

If you tell rpm to install all RPMs from some directory, then it does exactly this. rpm will not ignore RPMs listed for installation. You must manually remove the unneeded RPMs from the list (or directory). It will always overwrite the files with the "latest RPM installed" whichever order you do it in.

You can remove the old RPM and rpm will resolve the dependency with the newer version of the installed RPM. But this will only work, if none of the to be installed RPMs depends exactly on the old version.

If you really need different versions of the same RPM, then the RPM must be relocatable. You can then tell rpm to install the specific RPM to a different directory. If the files are not conflicting, then you can just install different versions with rpm -i (zypper in can not install different versions of the same RPM). I am packaging for example ruby gems as relocatable RPMs at work. So I can have different versions of the same gem installed.

I don't know on which files your RPMs are conflicting, but if all of them are "just" man pages, then you probably can simply overwrite the new ones with the old ones with rpm -i --replacefiles. The only problem with this would be, that it could confuse somebody who is reading the old man page and thinks it is for the actual version. Another problem would be the rpm --verify command. It will complain for the new package if the old one has overwritten some files.

Is this possibly a duplicate of https://serverfault.com/questions/522525/rpm-ignore-conflicts?

How do I create a MessageBox in C#?

This is some of the things you can put into a message box. Enjoy
MessageBox.Show("Enter the text for the message box",
"Enter the name of the message box",
(Enter the button names e.g. MessageBoxButtons.YesNo),
(Enter the icon e.g. MessageBoxIcon.Question),
(Enter the default button e.g. MessageBoxDefaultButton.Button1)

More information can be found here

How can I remove a pytz timezone from a datetime object?

To remove a timezone (tzinfo) from a datetime object:

# dt_tz is a datetime.datetime object
dt = dt_tz.replace(tzinfo=None)

If you are using a library like arrow, then you can remove timezone by simply converting an arrow object to to a datetime object, then doing the same thing as the example above.

# <Arrow [2014-10-09T10:56:09.347444-07:00]>
arrowObj = arrow.get('2014-10-09T10:56:09.347444-07:00')

# datetime.datetime(2014, 10, 9, 10, 56, 9, 347444, tzinfo=tzoffset(None, -25200))
tmpDatetime = arrowObj.datetime

# datetime.datetime(2014, 10, 9, 10, 56, 9, 347444)
tmpDatetime = tmpDatetime.replace(tzinfo=None)

Why would you do this? One example is that mysql does not support timezones with its DATETIME type. So using ORM's like sqlalchemy will simply remove the timezone when you give it a datetime.datetime object to insert into the database. The solution is to convert your datetime.datetime object to UTC (so everything in your database is UTC since it can't specify timezone) then either insert it into the database (where the timezone is removed anyway) or remove it yourself. Also note that you cannot compare datetime.datetime objects where one is timezone aware and another is timezone naive.

##############################################################################
# MySQL example! where MySQL doesn't support timezones with its DATETIME type!
##############################################################################

arrowObj = arrow.get('2014-10-09T10:56:09.347444-07:00')

arrowDt = arrowObj.to("utc").datetime

# inserts datetime.datetime(2014, 10, 9, 17, 56, 9, 347444, tzinfo=tzutc())
insertIntoMysqlDatabase(arrowDt)

# returns datetime.datetime(2014, 10, 9, 17, 56, 9, 347444)
dbDatetimeNoTz = getFromMysqlDatabase()

# cannot compare timzeone aware and timezone naive
dbDatetimeNoTz == arrowDt # False, or TypeError on python versions before 3.3

# compare datetimes that are both aware or both naive work however
dbDatetimeNoTz == arrowDt.replace(tzinfo=None) # True

How to vertically center <div> inside the parent element with CSS?

divs can't be vertically aligned that way, you can however use margins or position:relative to modify its location.

SQL Server Profiler - How to filter trace to only display events from one database?

Create a new template and check DBname. Use that template for your tracefile.

How can I save an image with PIL?

You should be able to simply let PIL get the filetype from extension, i.e. use:

j.save("C:/Users/User/Desktop/mesh_trans.bmp")

How can I remove the string "\n" from within a Ruby string?

When you want to remove a string, rather than replace it you can use String#delete (or its mutator equivalent String#delete!), e.g.:

x = "foo\nfoo"
x.delete!("\n")

x now equals "foofoo"

In this specific case String#delete is more readable than gsub since you are not actually replacing the string with anything.

malloc an array of struct pointers

array is a slightly misleading name. For a dynamically allocated array of pointers, malloc will return a pointer to a block of memory. You need to use Chess* and not Chess[] to hold the pointer to your array.

Chess *array = malloc(size * sizeof(Chess));
array[i] = NULL;

and perhaps later:

/* create new struct chess */
array[i] = malloc(sizeof(struct chess));

/* set up its members */
array[i]->size = 0;
/* etc. */

Check if value exists in enum in TypeScript

According to sandersn the best way to do this would be:

Object.values(MESSAGE_TYPE).includes(type as MESSAGE_TYPE)

SQL Server Pivot Table with multiple column aggregates

I used your own pivot as a nested query and came to this result:

SELECT
  [sub].[chardate],
  SUM(ISNULL([Australia], 0)) AS [Transactions Australia],
  SUM(CASE WHEN [Australia] IS NOT NULL THEN [TotalAmount] ELSE 0 END) AS [Amount Australia],
  SUM(ISNULL([Austria], 0)) AS [Transactions Austria],
  SUM(CASE WHEN [Austria] IS NOT NULL THEN [TotalAmount] ELSE 0 END) AS [Amount Austria]
FROM
(
  select * 
  from  mytransactions
  pivot (sum (totalcount) for country in ([Australia], [Austria])) as pvt
) AS [sub]
GROUP BY
  [sub].[chardate],
  [sub].[numericmonth]
ORDER BY 
  [sub].[numericmonth] ASC

Here is the Fiddle.

Why does git say "Pull is not possible because you have unmerged files"?

If you dont want to merge the changes and still want to update your local then run:

git reset --hard HEAD  

This will reset your local with HEAD and then pull your remote using git pull.

If you've already committed your merge locally (but haven't pushed to remote yet), and want to revert it as well:

git reset --hard HEAD~1 

PackagesNotFoundError: The following packages are not available from current channels:

If your base conda environment is active...

  • in which case "(base)" will most probably show at the start or your terminal command prompt.

... and pip is installed in your base environment ...

  • which it is: $ conda list | grep pip

... then install the not-found package simply by $ pip install <packagename>

java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader

Some old gradle tools cannot copy .so files into build folder by somehow, manually copying these files into build folder as below can solve the problem:

build/intermediates/rs/{build config}/{support architecture}/

build config: beta/production/sit/uat

support architecture: armeabi/armeabi-v7a/mips/x86

Select row and element in awk

To print the columns with a specific string, you use the // search pattern. For example, if you are looking for second columns that contains abc:

awk '$2 ~ /abc/'

... and if you want to print only a particular column:

awk '$2 ~ /abc/ { print $3 }'

... and for a particular line number:

awk '$2 ~ /abc/ && FNR == 5 { print $3 }'

Detect Browser Language in PHP

Unfortunately, none of the answers to this question takes into account some valid HTTP_ACCEPT_LANGUAGE such as:

  • q=0.8,en-US;q=0.5,en;q=0.3: having the q priority value at first place.
  • ZH-CN: old browsers that capitalise (wrongly) the whole langcode.
  • *: that basically say "serve whatever language you have".

After a comprehensive test with thousands of different Accept-Languages in my server, I ended up having this language detection method:

define('SUPPORTED_LANGUAGES', ['en', 'es']);

function detect_language() {
    foreach (preg_split('/[;,]/', $_SERVER['HTTP_ACCEPT_LANGUAGE']) as $sub) {
        if (substr($sub, 0, 2) == 'q=') continue;
        if (strpos($sub, '-') !== false) $sub = explode('-', $sub)[0];
        if (in_array(strtolower($sub), SUPPORTED_LANGUAGES)) return $sub;
    }
    return 'en';
}

Making a list of evenly spaced numbers in a certain range in python

Numpy's r_ convenience function can also create evenly spaced lists with syntax np.r_[start:stop:steps]. If steps is a real number (ending on j), then the end point is included, equivalent to np.linspace(start, stop, step, endpoint=1), otherwise not.

>>> np.r_[-1:1:6j, [0]*3, 5, 6]
array([-1. , -0.6, -0.2,  0.2,  0.6,  1.])

You can also directly concatente other arrays and also scalars:

>>> np.r_[-1:1:6j, [0]*3, 5, 6]
array([-1. , -0.6, -0.2,  0.2,  0.6,  1. ,  0. ,  0. ,  0. ,  5. ,  6. ])

Swift apply .uppercaseString to only the first letter of a string

extension String {
    var lowercased:String {
        var result = Array<Character>(self.characters);
        if let first = result.first { result[0] = Character(String(first).uppercaseString) }
        return String(result)
    }
}

Fit cell width to content

There are many ways to do this!

correct me if I'm wrong but the question is looking for this kind of result.

<table style="white-space:nowrap;width:100%;">
<tr>
<td class="block" style="width:50%">this should stretch</td>
<td class="block" style="width:50%">this should stretch</td>
<td class="block" style="width:auto">this should be the content width</td>
</tr>
</table>

The first 2 fields will "share" the remaining page (NOTE: if you add more text to either 50% fields it will take more space), and the last field will dominate the table constantly.

If you are happy to let text wrap you can move white-space:nowrap; to the style of the 3rd field
will be the only way to start a new line in that field.

alternatively, you can set a length on the last field ie. width:150px, and leave percentage's on the first 2 fields.

Hope this helps!

How can I convert uppercase letters to lowercase in Notepad++

I had to transfer texts from an Excel file to an xliff file. We had some texts that were originally in uppercase but those translators didn't use uppercase so I used notepad++ as intermediate to do the conversion.

Since I had the mouse in one hand (to mark in Excel and activate the different windows) I disliked the predefined shortcut (Ctrl+Shift+U) as "U" is too far away for my left hand. I first switched it to Ctrl+Shift+X which worked.

Then I realized, that you can create macros easily, so I recorded one doing:

  • mark all
  • paste from clipboard
  • convert to upppercase
  • copy to clipboard

That macro got assigned that very shortcut (Ctrl+Shift+X) and made my life easy :)

How can I find all the subsets of a set, with exactly n elements?

Using the canonical function to get the powerset from the the itertools recipe page:

from itertools import chain, combinations

def powerset(iterable):
    """
    powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)
    """
    xs = list(iterable)
    # note we return an iterator rather than a list
    return chain.from_iterable(combinations(xs,n) for n in range(len(xs)+1))

Used like:

>>> list(powerset("abc"))
[(), ('a',), ('b',), ('c',), ('a', 'b'), ('a', 'c'), ('b', 'c'), ('a', 'b', 'c')]

>>> list(powerset(set([1,2,3])))
[(), (1,), (2,), (3,), (1, 2), (1, 3), (2, 3), (1, 2, 3)]

map to sets if you want so you can use union, intersection, etc...:

>>> map(set, powerset(set([1,2,3])))
[set([]), set([1]), set([2]), set([3]), set([1, 2]), set([1, 3]), set([2, 3]), set([1, 2, 3])]

>>> reduce(lambda x,y: x.union(y), map(set, powerset(set([1,2,3]))))
set([1, 2, 3])

Bundler: Command not found

You can also create a symlink:

ln -s /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/bin/bundle /usr/bin/bundle

HTML5 and frameborder

As per the other posting here, the best solution is to use the CSS entry of

style="border:0;"

How to add buttons at top of map fragment API v2 layout

extending de Almeida's answer I am editing code little bit here. since previous code was hiding gps location icon I did following way which worked better.

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"

>

<RadioGroup 
    android:id="@+id/radio_group_list_selector"
    android:layout_width="match_parent"
    android:layout_height="48dp"
    android:orientation="horizontal" 
    android:background="#80000000"
    android:padding="4dp" >

    <RadioButton
        android:id="@+id/radioPopular"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:text="@string/Popular"
        android:gravity="center_horizontal|center_vertical"
        android:layout_weight="1"
        android:button="@null"
        android:background="@drawable/shape_radiobutton"
        android:textColor="@drawable/textcolor_radiobutton" />
    <View
        android:id="@+id/VerticalLine"
        android:layout_width="1dip"
        android:layout_height="match_parent"
        android:background="#aaa" />

    <RadioButton
        android:id="@+id/radioAZ"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:gravity="center_horizontal|center_vertical"
        android:text="@string/AZ"
        android:layout_weight="1"
        android:button="@null"
        android:background="@drawable/shape_radiobutton2"
        android:textColor="@drawable/textcolor_radiobutton" />

    <View
        android:id="@+id/VerticalLine"
        android:layout_width="1dip"
        android:layout_height="match_parent"
        android:background="#aaa" />

    <RadioButton
        android:id="@+id/radioCategory"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:gravity="center_horizontal|center_vertical"
        android:text="@string/Category"
        android:layout_weight="1"
        android:button="@null"
        android:background="@drawable/shape_radiobutton2"
        android:textColor="@drawable/textcolor_radiobutton" />
    <View
        android:id="@+id/VerticalLine"
        android:layout_width="1dip"
        android:layout_height="match_parent"
        android:background="#aaa" />

    <RadioButton
        android:id="@+id/radioNearBy"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:gravity="center_horizontal|center_vertical"
        android:text="@string/NearBy"
        android:layout_weight="1"
        android:button="@null"
        android:background="@drawable/shape_radiobutton3"
        android:textColor="@drawable/textcolor_radiobutton" />
</RadioGroup>

<fragment
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment"
    android:scrollbars="vertical" />

What is the difference between Cygwin and MinGW?

Cygwin is designed to provide a more-or-less complete POSIX environment for Windows, including an extensive set of tools designed to provide a full-fledged Linux-like platform. In comparison, MinGW and MSYS provide a lightweight, minimalist POSIX-like layer, with only the more essential tools like gcc and bash available. Because of MinGW's more minimalist approach, it does not provide the degree of POSIX API coverage Cygwin offers, and therefore cannot build certain programs which can otherwise be compiled on Cygwin.

In terms of the code generated by the two, the Cygwin toolchain relies on dynamic linking to a large runtime library, cygwin1.dll, while the MinGW toolchain compiles code to binaries that link dynamically to the Windows native C library msvcrt.dll as well as statically to parts of glibc. Cygwin executables are therefore more compact but require a separate redistributable DLL, while MinGW binaries can be shipped standalone but tend to be larger.

The fact that Cygwin-based programs require a separate DLL to run also leads to licensing restrictions. The Cygwin runtime library is licensed under GPLv3 with a linking exception for applications with OSI-compliant licenses, so developers wishing to build a closed-source application around Cygwin must acquire a commercial license from Red Hat. On the other hand, MinGW code can be used in both open-source and closed-source applications, as the headers and libraries are permissively licensed.

What is the difference between a database and a data warehouse?

A data warehouse is a TYPE of database.

In addition to what folks have already said, data warehouses tend to be OLAP, with indexes, etc. tuned for reading, not writing, and the data is de-normalized / transformed into forms that are easier to read & analyze.

Some folks have said "databases" are the same as OLTP -- this isn't true. OLTP, again, is a TYPE of database.

Other types of "databases": Text files, XML, Excel, CSV..., Flat Files :-)

Using Gradle to build a jar with dependencies

Update: In newer Gradle versions (4+) the compile qualifier is deprecated in favour of the new api and implementation configurations. If you use these, the following should work for you:

// Include dependent libraries in archive.
mainClassName = "com.company.application.Main"

jar {
  manifest { 
    attributes "Main-Class": "$mainClassName"
  }  

  from {
    configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) }
  }
}

For older gradle versions, or if you still use the "compile" qualifier for your dependencies, this should work:

// Include dependent libraries in archive.
mainClassName = "com.company.application.Main"

jar {
  manifest { 
    attributes "Main-Class": "$mainClassName"
  }  

  from {
    configurations.compile.collect { it.isDirectory() ? it : zipTree(it) }
  }
}

Note that mainClassName must appear BEFORE jar {.

ListBox with ItemTemplate (and ScrollBar!)

Thnaks for answer. I tried it myself too to an Empty Project and - lo behold allmighty creator of heaven and seven seas - it worked. I originally had ListBox inside which was inside of root . For some reason ListBox doesn't like being inside of StackPanel, at all! =)

-pom-

How to run an awk commands in Windows?

Actually, I do like mark instruction but little differently. I've added C:\Program Files (x86)\GnuWin32\bin\ to the Path variable, and try to run it with type awk using cmd.

Hope it works.

Can attributes be added dynamically in C#?

I don't believe so. Even if I'm wrong, the best you can hope for is adding them to an entire Type, never an instance of a Type.

What is the easiest way to get the current day of the week in Android?

Calendar.getInstance().get(Calendar.DAY_OF_WEEK)

or

new GregorianCalendar().get(Calendar.DAY_OF_WEEK);

Just the same as in Java, nothing particular to Android.

Using Apache httpclient for https

This is what worked for me:

    KeyStore keyStore  = KeyStore.getInstance("PKCS12");
    FileInputStream instream = new FileInputStream(new File("client-p12-keystore.p12"));
    try {
        keyStore.load(instream, "password".toCharArray());
    } finally {
        instream.close();
    }

    // Trust own CA and all self-signed certs
    SSLContext sslcontext = SSLContexts.custom()
        .loadKeyMaterial(keyStore, "password".toCharArray())
        //.loadTrustMaterial(trustStore, new TrustSelfSignedStrategy())
        .build();
    // Allow TLSv1 protocol only
    SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
        sslcontext,
        new String[] { "TLSv1" },
        null,
        SSLConnectionSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER); //TODO
    CloseableHttpClient httpclient = HttpClients.custom()
        .setHostnameVerifier(SSLConnectionSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER) //TODO
        .setSSLSocketFactory(sslsf)
        .build();
    try {

        HttpGet httpget = new HttpGet("https://localhost:8443/secure/index");

        System.out.println("executing request" + httpget.getRequestLine());

        CloseableHttpResponse response = httpclient.execute(httpget);
        try {
            HttpEntity entity = response.getEntity();

            System.out.println("----------------------------------------");
            System.out.println(response.getStatusLine());
            if (entity != null) {
                System.out.println("Response content length: " + entity.getContentLength());
            }
            EntityUtils.consume(entity);
        } finally {
            response.close();
        }
    } finally {
        httpclient.close();
    }
}

This code is a modified version of http://hc.apache.org/httpcomponents-client-4.3.x/httpclient/examples/org/apache/http/examples/client/ClientCustomSSL.java

No input file specified

In my case, there were an error in the php.ini open_basedir variable.

use regular expression in if-condition in bash

@OP,

Is glob pettern not only used for file names?

No, "glob" pattern is not only used for file names. you an use it to compare strings as well. In your examples, you can use case/esac to look for strings patterns.

 gg=svm-grid-ch 
 # looking for the word "grid" in the string $gg
 case "$gg" in
    *grid* ) echo "found";;
 esac

 # [[ $gg =~ ^....grid* ]]
 case "$gg" in ????grid*) echo "found";; esac 

 # [[ $gg =~ s...grid* ]]
 case "$gg" in s???grid*) echo "found";; esac

In bash, when to use glob pattern and when to use regular expression? Thanks!

Regex are more versatile and "convenient" than "glob patterns", however unless you are doing complex tasks that "globbing/extended globbing" cannot provide easily, then there's no need to use regex. Regex are not supported for version of bash <3.2 (as dennis mentioned), but you can still use extended globbing (by setting extglob ). for extended globbing, see here and some simple examples here.

Update for OP: Example to find files that start with 2 characters (the dots "." means 1 char) followed by "g" using regex

eg output

$ shopt -s dotglob
$ ls -1 *
abg
degree
..g

$ for file in *; do [[ $file =~ "..g" ]] && echo $file ; done
abg
degree
..g

In the above, the files are matched because their names contain 2 characters followed by "g". (ie ..g).

The equivalent with globbing will be something like this: (look at reference for meaning of ? and * )

$ for file in ??g*; do echo $file; done
abg
degree
..g

Using WGET to run a cronjob PHP

you can just use this code to hit the script using cron job using cpanel:

wget https://www.example.co.uk/unique-code

html cellpadding the left side of a cell

This is what css is for... HTML doesn't allow for unequal padding. When you say that you don't want to use style sheets, does this mean you're OK with inline css?

<table>
    <tr>
        <td style="padding: 5px 10px 5px 5px;">Content</td>
        <td style="padding: 5px 10px 5px 5px;">Content</td>
    </tr>
</table>

You could also use JS to do this if you're desperate not to use stylesheets for some reason.

Limit length of characters in a regular expression?

(^(\d{2})|^(\d{4})|^(\d{5}))$

This expression takes the number of length 2,4 and 5. Valid Inputs are 12 1234 12345

Display unescaped HTML in Vue.js

You can use the directive v-html to show it. like this:

<td v-html="desc"></td>

YouTube: How to present embed video with sound muted

Try this

<iframe width="420" height="315" src="http://www.youtube.com/embed/
HeQ39bLsoTI?autoplay=1&cc_load_policy=1" volume="0" frameborder="0"
allowfullscreen></iframe>

don't forget to write volume="0"

Set width of a "Position: fixed" div relative to parent div

Use this CSS:

#container {
    width: 400px;
    border: 1px solid red;
}

#fixed {
    position: fixed;
    width: inherit;
    border: 1px solid green;
}

The #fixed element will inherit it's parent width, so it will be 100% of that.

The type initializer for 'MyClass' threw an exception

Similar to what Muhammad Iqbal stated.. I was in a VB.NET (may also be C#) project where I did remove a key-value pair from the App.config which was referenced by a variable global to the Sub Main() of Module Main. Therefore, the exception (and break) occurs in Module Main before the Sub Main(). If only I had a break-point on the Dim, but we don't usually break on global variables. Perhaps a good reason not to declare globals referencing App.config? In other words, this...

An unhandled exception of type 'System.TypeInitializationException' occurred in Unknown Module. The type initializer for 'Namespace.Main' threw an exception.

Is caused by...

App.config

<connectionStrings>
    <!--<add name="ConnectionString1" connectionString="..." />-->

Main module

Module Main
    Dim cnnString As String = ConfigurationManager.ConnectionStrings("ConnectionString1")  '<-- BREAK HERE (EXCEPTION)

    Sub Main()

        // main code

    End Main
End Module

Global environment variables in a shell script

Run your script with .

. myscript.sh

This will run the script in the current shell environment.

export governs which variables will be available to new processes, so if you say

FOO=1
export BAR=2
./runScript.sh

then $BAR will be available in the environment of runScript.sh, but $FOO will not.

How can I disable ARC for a single file in a project?

Disable ARC on MULTIPLE files:

  1. Select desired files at Target/Build Phases/Compile Sources in Xcode
  2. PRESS ENTER
  3. Type -fno-objc-arc
  4. Press Enter or Done

;)

enter image description here

Can you split a stream into two streams?

Unfortunately, what you ask for is directly frowned upon in the JavaDoc of Stream:

A stream should be operated on (invoking an intermediate or terminal stream operation) only once. This rules out, for example, "forked" streams, where the same source feeds two or more pipelines, or multiple traversals of the same stream.

You can work around this using peek or other methods should you truly desire that type of behaviour. In this case, what you should do is instead of trying to back two streams from the same original Stream source with a forking filter, you would duplicate your stream and filter each of the duplicates appropriately.

However, you may wish to reconsider if a Stream is the appropriate structure for your use case.

Get Request and Session Parameters and Attributes from JSF pages

You can also use a tool like OcpSoft's PrettyFaces to inject dynamic parameter values directly into JSF Beans.

What do we mean by Byte array?

From wikipedia:

In computer science, an array data structure or simply array is a data structure consisting of a collection of elements (values or variables), each identified by one or more integer indices, stored so that the address of each element can be computed from its index tuple by a simple mathematical formula.

So when you say byte array, you're referring to an array of some defined length (e.g. number of elements) that contains a collection of byte (8 bits) sized elements.

In C# a byte array could look like:

byte[] bytes = { 3, 10, 8, 25 };

The sample above defines an array of 4 elements, where each element can be up to a Byte in length.

Java IOException "Too many open files"

Although in most general cases the error is quite clearly that file handles have not been closed, I just encountered an instance with JDK7 on Linux that well... is sufficiently ****ed up to explain here.

The program opened a FileOutputStream (fos), a BufferedOutputStream (bos) and a DataOutputStream (dos). After writing to the dataoutputstream, the dos was closed and I thought everything went fine.

Internally however, the dos, tried to flush the bos, which returned a Disk Full error. That exception was eaten by the DataOutputStream, and as a consequence the underlying bos was not closed, hence the fos was still open.

At a later stage that file was then renamed from (something with a .tmp) to its real name. Thereby, the java file descriptor trackers lost track of the original .tmp, yet it was still open !

To solve this, I had to first flush the DataOutputStream myself, retrieve the IOException and close the FileOutputStream myself.

I hope this helps someone.

Where is the .NET Framework 4.5 directory?

Whilst the above answers are correct its worth noting that MSBuild has changed and it no longer ships with the .net framework, it comes either stand alone or with visual studio. As a result it's binaries have moved... so the one you get under the 4.0.303619 directory is actually the old one!

I've just been caught out by this - I found automatic binding redirects were only working when running from VisualStudio but not when running msbuild from the command line... the clue was that binding redirects were added in VS 2013 (for that read .net framework 4.5). If you open up a vs command prompt you'll see it now gets it from program files as the other article mentions. Whereas I was using a batch file on my path which linked to the old version.

Version numbers

Under framework:

PS C:\Windows\Microsoft.NET\Framework\v4.0.30319> .\msbuild.exe -version
Microsoft (R) Build Engine version 4.0.30319.33440
[Microsoft .NET Framework, version 4.0.30319.34014]
Copyright (C) Microsoft Corporation. All rights reserved.

4.0.30319.33440PS C:\Windows\Microsoft.NET\Framework\v4.0.30319>

Under program files:

PS C:\Program Files (x86)\MSBuild\12.0\Bin> .\MSBuild.exe -version
Microsoft (R) Build Engine version 12.0.21005.1
[Microsoft .NET Framework, version 4.0.30319.34014]
Copyright (C) Microsoft Corporation. All rights reserved.

12.0.21005.1PS C:\Program Files (x86)\MSBuild\12.0\Bin>

Can I concatenate multiple MySQL rows into one field?

For somebody looking here how to use GROUP_CONCAT with subquery - posting this example

SELECT i.*,
(SELECT GROUP_CONCAT(userid) FROM favourites f WHERE f.itemid = i.id) AS idlist
FROM items i
WHERE i.id = $someid

So GROUP_CONCAT must be used inside the subquery, not wrapping it.

Disabling swap files creation in vim

You can set backupdir and directory to null in order to completely disable your swap files, but it is generally recommended to simply put them in a centralized directory. Vim takes care of making sure that there aren't name collissions or anything like that; so, this is a completely safe alternative:

set backupdir=~/.vim/backup/
set directory=~/.vim/backup/

How to get the last N rows of a pandas DataFrame?

Don't forget DataFrame.tail! e.g. df1.tail(10)

Semi-transparent color layer over background-image?

You need then a wrapping element with the bg image and in it the content element with the bg color:

<div id="Wrapper">
  <div id="Content">
    <!-- content here -->
  </div>
</div>

and the css:

#Wrapper{
    background:url(../img/bg/diagonalnoise.png); 
    width:300px; 
    height:300px;
}

#Content{
    background-color:rgba(248,247,216,0.7); 
    width:100%; 
    height:100%;
}

How to select rows with NaN in particular column?

@qbzenker provided the most idiomatic method IMO

Here are a few alternatives:

In [28]: df.query('Col2 != Col2') # Using the fact that: np.nan != np.nan
Out[28]:
   Col1  Col2  Col3
1     0   NaN   0.0

In [29]: df[np.isnan(df.Col2)]
Out[29]:
   Col1  Col2  Col3
1     0   NaN   0.0

Make REST API call in Swift

edited for swift 2

let url = NSURL(string: "http://www.test.com")

    let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
        print(NSString(data: data!, encoding: NSUTF8StringEncoding))
    }

    task.resume()

Start an external application from a Google Chrome Extension?

Question has a good pagerank on google, so for anyone who's looking for answer to this question this might be helpful.

There is an extension in google chrome marketspace to do exactly that: https://chrome.google.com/webstore/detail/hccmhjmmfdfncbfpogafcbpaebclgjcp

android.app.Application cannot be cast to android.app.Activity

in case your project use dagger, and then this error show up you can add this at android manifest

   <application
        ...
        android: name = ".BaseApplication"
        ...> ...

How to resolve conflicts in EGit

To resolve the conflicts, use Git stash to save away your uncommitted changes; then pull down the remote repository change set; then pop your local stash to reapply your uncommitted changes.

In Eclipse v4.5 (Mars) to stash changes (a relatively recent addition, wasn't in previous EGit) I do this: right-click on a top-level Eclipse project that's in Git control, pick Team, pick Stashes, pick Stash Changes; a dialog opens to request a stash commit message.

You must use the context menu on a top level project! If I right click on a directory or file within a Git-controlled project I don't get the appropriate context menu.

Jmeter - Run .jmx file through command line and get the summary report in a excel

This would be the command line statement.

"%JMETER_HOME%\bin\jmeter.bat" -n -t <jmx test file path> -l <csv result file path> -Djmeter.save.saveservice.output_format=csv

How to run a shell script in OS X by double-clicking?

Alternatively, you could create a regular Mac OS X application from your script using Platypus

git stash apply version

If one is on a Windows machine and in PowerShell, one needs to quote the argument such as:

git stash apply "stash@{0}"

...or to apply the changes and remove from the stash:

git stash pop "stash@{0}"

Otherwise without the quotes you might get this error:

fatal: ambiguous argument 'stash@': unknown revision or path not in the working tree.

Moving average or running mean

I know this is an old question, but here is a solution that doesn't use any extra data structures or libraries. It is linear in the number of elements of the input list and I cannot think of any other way to make it more efficient (actually if anyone knows of a better way to allocate the result, please let me know).

NOTE: this would be much faster using a numpy array instead of a list, but I wanted to eliminate all dependencies. It would also be possible to improve performance by multi-threaded execution

The function assumes that the input list is one dimensional, so be careful.

### Running mean/Moving average
def running_mean(l, N):
    sum = 0
    result = list( 0 for x in l)

    for i in range( 0, N ):
        sum = sum + l[i]
        result[i] = sum / (i+1)

    for i in range( N, len(l) ):
        sum = sum - l[i-N] + l[i]
        result[i] = sum / N

    return result

Example

Assume that we have a list data = [ 1, 2, 3, 4, 5, 6 ] on which we want to compute a rolling mean with period of 3, and that you also want a output list that is the same size of the input one (that's most often the case).

The first element has index 0, so the rolling mean should be computed on elements of index -2, -1 and 0. Obviously we don't have data[-2] and data[-1] (unless you want to use special boundary conditions), so we assume that those elements are 0. This is equivalent to zero-padding the list, except we don't actually pad it, just keep track of the indices that require padding (from 0 to N-1).

So, for the first N elements we just keep adding up the elements in an accumulator.

result[0] = (0 + 0 + 1) / 3  = 0.333    ==   (sum + 1) / 3
result[1] = (0 + 1 + 2) / 3  = 1        ==   (sum + 2) / 3
result[2] = (1 + 2 + 3) / 3  = 2        ==   (sum + 3) / 3

From elements N+1 forwards simple accumulation doesn't work. we expect result[3] = (2 + 3 + 4)/3 = 3 but this is different from (sum + 4)/3 = 3.333.

The way to compute the correct value is to subtract data[0] = 1 from sum+4, thus giving sum + 4 - 1 = 9.

This happens because currently sum = data[0] + data[1] + data[2], but it is also true for every i >= N because, before the subtraction, sum is data[i-N] + ... + data[i-2] + data[i-1].

Setting default value for TypeScript object passed as argument

Actually, there appears to now be a simple way. The following code works in TypeScript 1.5:

function sayName({ first, last = 'Smith' }: {first: string; last?: string }): void {
  const name = first + ' ' + last;
  console.log(name);
}

sayName({ first: 'Bob' });

The trick is to first put in brackets what keys you want to pick from the argument object, with key=value for any defaults. Follow that with the : and a type declaration.

This is a little different than what you were trying to do, because instead of having an intact params object, you have instead have dereferenced variables.

If you want to make it optional to pass anything to the function, add a ? for all keys in the type, and add a default of ={} after the type declaration:

function sayName({first='Bob',last='Smith'}: {first?: string; last?: string}={}){
    var name = first + " " + last;
    alert(name);
}

sayName();

htaccess redirect all pages to single page

Add this for pages not currently on your site...

ErrorDocument 404 http://example.com/

Along with your Redirect 301 / http://www.thenewdomain.com/ that should cover all the bases...

Good luck!

How can I access an internal class from an external assembly?

I would like to argue one point - that you cannot augment the original assembly - using Mono.Cecil you can inject [InternalsVisibleTo(...)] to the 3pty assembly. Note there might be legal implications - you're messing with 3pty assembly and technical implications - if the assembly has strong name you either need to strip it or re-sign it with different key.

 Install-Package Mono.Cecil

And the code like:

static readonly string[] s_toInject = {
  // alternatively "MyAssembly, PublicKey=0024000004800000... etc."
  "MyAssembly"
};

static void Main(string[] args) {
  const string THIRD_PARTY_ASSEMBLY_PATH = @"c:\folder\ThirdPartyAssembly.dll";

   var parameters = new ReaderParameters();
   var asm = ModuleDefinition.ReadModule(INPUT_PATH, parameters);
   foreach (var toInject in s_toInject) {
     var ca = new CustomAttribute(
       asm.Import(typeof(InternalsVisibleToAttribute).GetConstructor(new[] {
                      typeof(string)})));
     ca.ConstructorArguments.Add(new CustomAttributeArgument(asm.TypeSystem.String, toInject));
     asm.Assembly.CustomAttributes.Add(ca);
   }
   asm.Write(@"c:\folder-modified\ThirdPartyAssembly.dll");
   // note if the assembly is strongly-signed you need to resign it like
   // asm.Write(@"c:\folder-modified\ThirdPartyAssembly.dll", new WriterParameters {
   //   StrongNameKeyPair = new StrongNameKeyPair(File.ReadAllBytes(@"c:\MyKey.snk"))
   // });
}

How do I join two lines in vi?

Vi or Vim?

Anyway, the following command works for Vim in 'nocompatible' mode. That is, I suppose, almost pure vi.

:join!

If you want to do it from normal command use

gJ

With 'gJ' you join lines as is -- without adding or removing whitespaces:

S<Switch_ID>_F<File type>
_ID<ID number>_T<date+time>_O<Original File name>.DAT

Result:

S<Switch_ID>_F<File type>_ID<ID number>_T<date+time>_O<Original File name>.DAT

With 'J' command you will have:

S<Switch_ID>_F<File type> _ID<ID number>_T<date+time>_O<Original File name>.DAT

Note space between type> and _ID.

Youtube - How to force 480p video quality in embed link / <iframe>

I found that as of May, 2012, if you set the frame size so that the minimum pixel area (width • height) is above a certain threshold, it bumps the quality up from 360p to 480p, if you're video is at least 640 x 360.

I've discovered that setting a frame size to 780 x 480 for the embed frame triggers the 480p quality, without distorting the video (scaling up). 640 x 585 also works in this manner. I also used the &hd=1 parameter, but I doubt this has much control if your video is not uploaded in HD (720p or higher).

For instance:

<iframe width="780" height="480" src="http://www.youtube.com/embed/[VIDEO-ID]?rel=0&fs=1&showinfo=0&autohide=1&hd=1"></iframe>

Of course, the drawback is that by setting these static frame dimensions, you will most likely get black bars on the sides or above and below, depending on what you prefer.

If you didn't care about the controls being cut-off, you could go on to use CSS and overflow: hidden to crop the black bars out of the frame, providing you know the exact dimensions of the video.

Hope this helps, and hope the Embed method soon gets discrete quality parameters again one day!

iTunes Connect: How to choose a good SKU?

Might be answer is late but look at Simple Information of SKU (Stock keeping unit) number is, it's an unique tracking number (an arbi­trary num­ber) that are used in appStore for your application. You can put what­ever you want in there as long as it is unique among your appli­ca­tions. Try to fol­low a pat­tern for the SKU Num­ber of your apps so that you will be able to bet­ter orga­nize them. I sug­gest a com­bi­na­tion of the cur­rent year + month + ID for your app. So if you’re devel­op­ing your first appli­ca­tion on september 1991 (oh,, yah it's my b'day's month and year :D ), you could put your SKU Num­ber as “19910901”. Here, I am just suggesting you for this pattern but you can take/choose any pattern which easy for you.

How to add a column in TSQL after a specific column?

/* Script to change the column order of a table
Note this will create a new table to replace the original table
HOWEVER it doesn't copy the triggers or other table properties - just the data
*/

Generate a new table with the columns in the order that you require

Select Column2, Column1, Column3 Into NewTable from OldTable

Delete the original table

Drop Table OldTable;

Rename the new table

EXEC sp_rename 'NewTable', 'OldTable';

Python TypeError: cannot convert the series to <class 'int'> when trying to do math on dataframe

Seems your initial data contains strings and not numbers. It would probably be best to ensure that the data is already of the required type up front.

However, you can convert strings to numbers like this:

pd.Series(['123', '42']).astype(float)

instead of float(series)

Why is AJAX returning HTTP status code 0?

I found another case where jquery gives you status code 0 -- if for some reason XMLHttpRequest is not defined, you'll get this error.

Obviously this won't normally happen on the web, but a bug in a nightly firefox build caused this to crop up in an add-on I was writing. :)

SQL Server add auto increment primary key to existing table

When we add and identity column in an existing table it will automatically populate no need to populate it manually.

What does it mean to "call" a function in Python?

I'll give a slightly advanced answer. In Python, functions are first-class objects. This means they can be "dynamically created, destroyed, passed to a function, returned as a value, and have all the rights as other variables in the programming language have."

Calling a function/class instance in Python means invoking the __call__ method of that object. For old-style classes, class instances are also callable but only if the object which creates them has a __call__ method. The same applies for new-style classes, except there is no notion of "instance" with new-style classes. Rather they are "types" and "objects".

As quoted from the Python 2 Data Model page, for function objects, class instances(old style classes), and class objects(new-style classes), "x(arg1, arg2, ...) is a shorthand for x.__call__(arg1, arg2, ...)".

Thus whenever you define a function with the shorthand def funcname(parameters): you are really just creating an object with a method __call__ and the shorthand for __call__ is to just name the instance and follow it with parentheses containing the arguments to the call. Because functions are first class objects in Python, they can be created on the fly with dynamic parameters (and thus accept dynamic arguments). This comes into handy with decorator functions/classes which you will read about later.

For now I suggest reading the Official Python Tutorial.

How to create json by JavaScript for loop?

From what I understand of your request, this should work:

<script>
//  var status  = document.getElementsByID("uniqueID"); // this works too
var status  = document.getElementsByName("status")[0];
var jsonArr = [];

for (var i = 0; i < status.options.length; i++) {
    jsonArr.push({
        id: status.options[i].text,
        optionValue: status.options[i].value
    });
}
</script>

Sort array by firstname (alphabetically) in Javascript

You can use something similar, to get rid of case sensitive

users.sort(function(a, b){

  //compare two values
  if(a.firstname.toLowerCase() < b.firstname.toLowerCase()) return -1;
  if(a.firstname.toLowerCase() > b.firstname.toLowerCase()) return 1;
  return 0;

})

lambda expression join multiple tables with select and where clause

I was looking for something and I found this post. I post this code that managed many-to-many relationships in case someone needs it.

    var UserInRole = db.UsersInRoles.Include(u => u.UserProfile).Include(u => u.Roles)
    .Select (m => new 
    {
        UserName = u.UserProfile.UserName,
        RoleName = u.Roles.RoleName
    });

How to check if a String contains another String in a case insensitive manner in Java?

Here's some Unicode-friendly ones you can make if you pull in ICU4j. I guess "ignore case" is questionable for the method names because although primary strength comparisons do ignore case, it's described as the specifics being locale-dependent. But it's hopefully locale-dependent in a way the user would expect.

public static boolean containsIgnoreCase(String haystack, String needle) {
    return indexOfIgnoreCase(haystack, needle) >= 0;
}

public static int indexOfIgnoreCase(String haystack, String needle) {
    StringSearch stringSearch = new StringSearch(needle, haystack);
    stringSearch.getCollator().setStrength(Collator.PRIMARY);
    return stringSearch.first();
}

Should a function have only one return statement?

Structured programming says you should only ever have one return statement per function. This is to limit the complexity. Many people such as Martin Fowler argue that it is simpler to write functions with multiple return statements. He presents this argument in the classic refactoring book he wrote. This works well if you follow his other advice and write small functions. I agree with this point of view and only strict structured programming purists adhere to single return statements per function.

UTF-8 problems while reading CSV file with fgetcsv

Try putting this into the top of your file (before any other output):

<?php

header('Content-Type: text/html; charset=UTF-8');

?>

How to allow remote access to my WAMP server for Mobile(Android)

I assume you are using windows. Open the command prompt and type ipconfig and find out your local address (on your pc) it should look something like 192.168.1.13 or 192.168.0.5 where the end digit is the one that changes. It should be next to IPv4 Address.

If your WAMP does not use virtual hosts the next step is to enter that IP address on your phones browser ie http://192.168.1.13 If you have a virtual host then you will need root to edit the hosts file.

If you want to test the responsiveness / mobile design of your website you can change your user agent in chrome or other browsers to mimic a mobile.

See http://googlesystem.blogspot.co.uk/2011/12/changing-user-agent-new-google-chrome.html.

Edit: Chrome dev tools now has a mobile debug tool where you can change the size of the viewport, spoof user agents, connections (4G, 3G etc).

If you get forbidden access then see this question WAMP error: Forbidden You don't have permission to access /phpmyadmin/ on this server. Basically, change the occurrances of deny,allow to allow,deny in the httpd.conf file. You can access this by the WAMP menu.

To eliminate possible causes of the issue for now set your config file to

<Directory />
    Options FollowSymLinks
    AllowOverride All
    Order allow,deny
    Allow from all
    <RequireAll>
        Require all granted
    </RequireAll>
</Directory>

As thatis working for my windows PC, if you have the directory config block as well change that also to allow all.

Config file that fixed the problem:

https://gist.github.com/samvaughton/6790739

Problem was that the /www apache directory config block still had deny set as default and only allowed from localhost.

How to sort two lists (which reference each other) in the exact same way

One classic approach to this problem is to use the "decorate, sort, undecorate" idiom, which is especially simple using python's built-in zip function:

>>> list1 = [3,2,4,1, 1]
>>> list2 = ['three', 'two', 'four', 'one', 'one2']
>>> list1, list2 = zip(*sorted(zip(list1, list2)))
>>> list1
(1, 1, 2, 3, 4)
>>> list2 
('one', 'one2', 'two', 'three', 'four')

These of course are no longer lists, but that's easily remedied, if it matters:

>>> list1, list2 = (list(t) for t in zip(*sorted(zip(list1, list2))))
>>> list1
[1, 1, 2, 3, 4]
>>> list2
['one', 'one2', 'two', 'three', 'four']

It's worth noting that the above may sacrifice speed for terseness; the in-place version, which takes up 3 lines, is a tad faster on my machine for small lists:

>>> %timeit zip(*sorted(zip(list1, list2)))
100000 loops, best of 3: 3.3 us per loop
>>> %timeit tups = zip(list1, list2); tups.sort(); zip(*tups)
100000 loops, best of 3: 2.84 us per loop

On the other hand, for larger lists, the one-line version could be faster:

>>> %timeit zip(*sorted(zip(list1, list2)))
100 loops, best of 3: 8.09 ms per loop
>>> %timeit tups = zip(list1, list2); tups.sort(); zip(*tups)
100 loops, best of 3: 8.51 ms per loop

As Quantum7 points out, JSF's suggestion is a bit faster still, but it will probably only ever be a little bit faster, because Python uses the very same DSU idiom internally for all key-based sorts. It's just happening a little closer to the bare metal. (This shows just how well optimized the zip routines are!)

I think the zip-based approach is more flexible and is a little more readable, so I prefer it.

The difference between sys.stdout.write and print?

print is just a thin wrapper that formats the inputs (modifiable, but by default with a space between args and newline at the end) and calls the write function of a given object. By default this object is sys.stdout, but you can pass a file using the "chevron" form. For example:

print >> open('file.txt', 'w'), 'Hello', 'World', 2+3

See: https://docs.python.org/2/reference/simple_stmts.html?highlight=print#the-print-statement


In Python 3.x, print becomes a function, but it is still possible to pass something other than sys.stdout thanks to the fileargument.

print('Hello', 'World', 2+3, file=open('file.txt', 'w'))

See https://docs.python.org/3/library/functions.html#print


In Python 2.6+, print is still a statement, but it can be used as a function with

from __future__ import print_function

Update: Bakuriu commented to point out that there is a small difference between the print function and the print statement (and more generally between a function and a statement).

In case of an error when evaluating arguments:

print "something", 1/0, "other" #prints only something because 1/0 raise an Exception

print("something", 1/0, "other") #doesn't print anything. The function is not called

How to Update Date and Time of Raspberry Pi With out Internet

Thanks for the replies.
What I did was,
1. I install meinberg ntp software application on windows 7 pc. (softros ntp server is also possible.)
2. change raspberry pi ntp.conf file (for auto update date and time)

server xxx.xxx.xxx.xxx iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst

3. If you want to make sure that date and time update at startup run this python script in rpi,

import os

try:
    client = ntplib.NTPClient()
    response = client.request('xxx.xxx.xxx.xxx', version=4)
    print "===================================="
    print "Offset : "+str(response.offset)
    print "Version : "+str(response.version)
    print "Date Time : "+str(ctime(response.tx_time))
    print "Leap : "+str(ntplib.leap_to_text(response.leap))
    print "Root Delay : "+str(response.root_delay)
    print "Ref Id : "+str(ntplib.ref_id_to_text(response.ref_id))
    os.system("sudo date -s '"+str(ctime(response.tx_time))+"'")
    print "===================================="
except:
    os.system("sudo date")
    print "NTP Server Down Date Time NOT Set At The Startup"
    pass

I found more info in raspberry pi forum.

Adjusting the Xcode iPhone simulator scale and size

With Xcode 9 - Simulator, you can pick & drag any corner of simulator to resize it and set according to your requirement.

Look at this snapshot.

enter image description here


Note: With Xcode 9.1+, Simulator scale options are changed.


Keyboard short-keys:
According to Xcode 9.1+

Physical Size       ? 1      command + 1
Pixel Accurate      ? 2      command + 2


According to Xcode 9

50% Scale           ? 1      command + 1
100% Scale          ? 2      command + 2
200% Scale          ? 3      command + 3

Simulator scale options from Xcode Menu:

Xcode 9.1+:
Menubar ? Window ? "Here, options available change simulator scale" (Physical Size & Pixel Accurate)

Pixel Accurate: Resizes your simulator to actual (Physical) device's pixels, if your mac system display screen size (pixel) supports that much high resolution, else this option will remain disabled.

Tip: rotate simulator ( ? + ? or ? + ? ), if Pixel Accurate is disabled. It may be enabled (if it fits to screen) in landscape.

enter image description here


Xcode 9.0
Menubar ? Window ? Scale ? "Here, options available change simulator scale"

enter image description here


Tip: How do you get screen shot with 100% (a scale with actual device size) that can be uploaded on AppStore?

Disable 'Optimize Rendering for Window scale' from Debug menu, before you take a screen shot (See here: How to take screenshots in the iOS simulator)

There is an option

Menubar ? Debug ? Disable "Optimize Rendering for Window scale"

enter image description here


Here is Apple's document: Resize a simulator window

How do I copy items from list to list without foreach?

And this is if copying a single property to another list is needed:

targetList.AddRange(sourceList.Select(i => i.NeededProperty));

javax.xml.bind.JAXBException: Class *** nor any of its super class is known to this context

I know that it's an old question, but you can change the Response using a parameter (P):

public class Response<P> implements Serializable{

private static final long serialVersionUID = 1L;

public enum MessageCode {
    SUCCESS, ERROR, UNKNOWN
}

private MessageCode code;
private String message;
private P payload;

...
public P getPayload() {
    return payload;
}

public void setPayload(P payload) {
    this.payload = payload;
}

}

The method would be

public Response<Departments> getDepartments(){...}

I can't try it now but it should works.

Otherwise it's possible to extends Response

@XmlRootElement    
public class DepResponse extends Response<Department> {<no content>}

get url content PHP

original answer moved to this topic .

Difference between .keystore file and .jks file

One reason to choose .keystore over .jks is that Unity recognizes the former but not the latter when you're navigating to select your keystore file (Unity 2017.3, macOS).

Align nav-items to right side in bootstrap-4

In last versions, it is easier. Just put a ml-auto class in the ul like so:

<ul class="nav navbar-nav ml-auto">

The transaction manager has disabled its support for remote/network transactions

I post the below solution here because after some searching this is where I landed, so other may too. I was trying to use EF 6 to call a stored procedure, but had a similar error because the stored procedure had a linked server being utilized.

The operation could not be performed because OLE DB provider _ for linked server _ was unable to begin a distributed transaction

The partner transaction manager has disabled its support for remote/network transactions*

Jumping over to SQL Client did fix my issue, which also confirmed for me that it was an EF thing.

EF model generated method based attempt:

db.SomeStoredProcedure();

ExecuteSqlCommand based attempt:

db.Database.ExecuteSqlCommand("exec [SomeDB].[dbo].[SomeStoredProcedure]");

With:

var connectionString = db.Database.Connection.ConnectionString;
var connection = new System.Data.SqlClient.SqlConnection(connectionString);    
var cmd = connection.CreateCommand();
cmd.CommandText = "exec [SomeDB].[dbo].[SomeStoredProcedure]";

connection.Open();
var result = cmd.ExecuteNonQuery();

That code can be shortened, but I think that version is slightly more convenient for debugging and stepping through.

I don't believe that Sql Client is necessarily a preferred choice, but I felt this was at least worth sharing if anyone else having similar problems gets landed here by google.

The above Code is C#, but the concept of trying to switch over to Sql Client still applies. At the very least it will be diagnostic to attempt to do so.

What difference is there between WebClient and HTTPWebRequest classes in .NET?

WebClient is a higher-level abstraction built on top of HttpWebRequest to simplify the most common tasks. For instance, if you want to get the content out of an HttpWebResponse, you have to read from the response stream:

var http = (HttpWebRequest)WebRequest.Create("http://example.com");
var response = http.GetResponse();

var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
var content = sr.ReadToEnd();

With WebClient, you just do DownloadString:

var client = new WebClient();
var content = client.DownloadString("http://example.com");

Note: I left out the using statements from both examples for brevity. You should definitely take care to dispose your web request objects properly.

In general, WebClient is good for quick and dirty simple requests and HttpWebRequest is good for when you need more control over the entire request.

How to check if array is not empty?

If you are talking about Python's actual array (available through import array from array), then the principle of least astonishment applies and you can check whether it is empty the same way you'd check if a list is empty.

from array import array
an_array = array('i') # an array of ints

if an_array:
    print("this won't be printed")

an_array.append(3)

if an_array:
    print("this will be printed")

SFTP file transfer using Java JSch

Usage:

sftp("file:/C:/home/file.txt", "ssh://user:pass@host/home");
sftp("ssh://user:pass@host/home/file.txt", "file:/C:/home");

Implementation

Enable tcp\ip remote connections to sql server express already installed database with code or script(query)

I recommend to use SMO (Enable TCP/IP Network Protocol for SQL Server). However, it was not available in my case.

I rewrote the WMI commands from Krzysztof Kozielczyk to PowerShell.

# Enable TCP/IP

Get-CimInstance -Namespace root/Microsoft/SqlServer/ComputerManagement10 -ClassName ServerNetworkProtocol -Filter "InstanceName = 'SQLEXPRESS' and ProtocolName = 'Tcp'" |
Invoke-CimMethod -Name SetEnable

# Open the right ports in the firewall
New-NetFirewallRule -DisplayName 'MSSQL$SQLEXPRESS' -Direction Inbound -Action Allow -Protocol TCP -LocalPort 1433

# Modify TCP/IP properties to enable an IP address

$properties = Get-CimInstance -Namespace root/Microsoft/SqlServer/ComputerManagement10 -ClassName ServerNetworkProtocolProperty -Filter "InstanceName='SQLEXPRESS' and ProtocolName = 'Tcp' and IPAddressName='IPAll'"
$properties | ? { $_.PropertyName -eq 'TcpPort' } | Invoke-CimMethod -Name SetStringValue -Arguments @{ StrValue = '1433' }
$properties | ? { $_.PropertyName -eq 'TcpPortDynamic' } | Invoke-CimMethod -Name SetStringValue -Arguments @{ StrValue = '' }

# Restart SQL Server

Restart-Service 'MSSQL$SQLEXPRESS'

2 column div layout: right column with fixed width, left fluid

See http://www.alistapart.com/articles/negativemargins/ , this is exactly what you need (example 4 there).

<div id="container">
    <div id="content">
        <h1>content</h1>
        <p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Phasellus varius eleifend tellus. Suspendisse potenti. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos hymenaeos. Nulla facilisi. Sed wisi lectus, placerat nec, mollis quis, posuere eget, arcu.</p>
        <p class="last">Donec euismod. Praesent mauris mi, adipiscing non, mollis eget, adipiscing ac, erat. Integer nonummy mauris sit amet metus. In adipiscing, ligula ultrices dictum vehicula, eros turpis lacinia libero, sed aliquet urna diam sed tellus. Etiam semper sapien eget metus.</p>
    </div>
</div>

<div id="sidebar">
    <h1>sidebar</h1>
    <ul>
        <li>link one</li>
        <li>link two</li>
    </ul>
</div>

#container {
    width: 100%;
    background: #f1f2ea url(background.gif) repeat-y right;
    float: left;
    margin-right: -200px;
}
#content {
    background: #f1f2ea;
    margin-right: 200px;
}
#sidebar {
    width: 200px;
    float: right;

cancelling a handler.postdelayed process

Hope this gist help https://gist.github.com/imammubin/a587192982ff8db221da14d094df6fb4

MainActivity as Screen Launcher with handler & runnable function, the Runnable run to login page or feed page with base preference login user with firebase.

Shell Script: Execute a python program from within a shell script

I use this and it works fine

#/bin/bash
/usr/bin/python python python_script.py

How can I list all foreign keys referencing a given table in SQL Server?

List of all foreign keys referencing a given table in SQL Server :

You can get the referencing table name and column name through following query...

SELECT 
   OBJECT_NAME(f.parent_object_id) TableName,
   COL_NAME(fc.parent_object_id,fc.parent_column_id) ColName
FROM 
   sys.foreign_keys AS f
INNER JOIN 
   sys.foreign_key_columns AS fc 
      ON f.OBJECT_ID = fc.constraint_object_id
INNER JOIN 
   sys.tables t 
      ON t.OBJECT_ID = fc.referenced_object_id
WHERE 
   OBJECT_NAME (f.referenced_object_id) = 'TableName'

And following screenshot for your understanding...

enter image description here

"cannot resolve symbol R" in Android Studio

After I do "Build->clean project" and "Sync project with gradle". Both them are not resolve. I down build gradle version from 3.3.0 => 3.2.1 (revert as project init state) and it resolve my problem.

How do I make a MySQL database run completely in memory?

It is also possible to place the MySQL data directory in a tmpfs in thus speeding up the database write and read calls. It might not be the most efficient way to do this but sometimes you can't just change the storage engine.

Here is my fstab entry for my MySQL data directory

none            /opt/mysql/server-5.6/data  tmpfs   defaults,size=1000M,uid=999,gid=1000,mode=0700          0       0

You may also want to take a look at the innodb_flush_log_at_trx_commit=2 setting. Maybe this will speedup your MySQL sufficently.

innodb_flush_log_at_trx_commit changes the mysql disk flush behaviour. When set to 2 it will only flush the buffer every second. By default each insert will cause a flush and thus cause more IO load.

Check if string contains only digits

This is what you want

function isANumber(str){
  return !/\D/.test(str);
}

How to split comma separated string using JavaScript?

Use

YourCommaSeparatedString.split(',');

How to reload / refresh model data from the server programmatically?

You're half way there on your own. To implement a refresh, you'd just wrap what you already have in a function on the scope:

function PersonListCtrl($scope, $http) {
  $scope.loadData = function () {
     $http.get('/persons').success(function(data) {
       $scope.persons = data;
     });
  };

  //initial load
  $scope.loadData();
}

then in your markup

<div ng-controller="PersonListCtrl">
    <ul>
        <li ng-repeat="person in persons">
            Name: {{person.name}}, Age {{person.age}}
        </li>
    </ul>
   <button ng-click="loadData()">Refresh</button>
</div>

As far as "accessing your model", all you'd need to do is access that $scope.persons array in your controller:

for example (just puedo code) in your controller:

$scope.addPerson = function() {
     $scope.persons.push({ name: 'Test Monkey' });
};

Then you could use that in your view or whatever you'd want to do.

VBA: activating/selecting a worksheet/row/cell

This is just a sample code, but it may help you get on your way:

Public Sub testIt()
    Workbooks("Workbook2").Activate
    ActiveWorkbook.Sheets("Sheet2").Activate
    ActiveSheet.Range("B3").Select
    ActiveCell.EntireRow.Insert
End Sub

I am assuming that you can open the book (called Workbook2 in the example).


I think (but I'm not sure) you can squash all this in a single line of code:

    Workbooks("Workbook2").Sheets("Sheet2").Range("B3").EntireRow.Insert

This way you won't need to activate the workbook (or sheet or cell)... Obviously, the book has to be open.

hash function for string

First, you generally do not want to use a cryptographic hash for a hash table. An algorithm that's very fast by cryptographic standards is still excruciatingly slow by hash table standards.

Second, you want to ensure that every bit of the input can/will affect the result. One easy way to do that is to rotate the current result by some number of bits, then XOR the current hash code with the current byte. Repeat until you reach the end of the string. Note that you generally do not want the rotation to be an even multiple of the byte size either.

For example, assuming the common case of 8 bit bytes, you might rotate by 5 bits:

int hash(char const *input) { 
    int result = 0x55555555;

    while (*input) { 
        result ^= *input++;
        result = rol(result, 5);
    }
}

Edit: Also note that 10000 slots is rarely a good choice for a hash table size. You usually want one of two things: you either want a prime number as the size (required to ensure correctness with some types of hash resolution) or else a power of 2 (so reducing the value to the correct range can be done with a simple bit-mask).

jQuery convert line breaks to br (nl2br equivalent)

In the spirit of changing the rendering instead of changing the content, the following CSS makes each newline behave like a <br>:

white-space: pre;
white-space: pre-line;

Why two rules: pre-line only affects newlines (thanks for the clue, @KevinPauli). IE6-7 and other old browsers fall back to the more extreme pre which also includes nowrap and renders multiple spaces. Details on these and other settings (pre-wrap) at mozilla and css-tricks (thanks @Sablefoste).

While I'm generally averse to the S.O. predilection for second-guessing the question rather than answering it, in this case replacing newlines with <br> markup may increase vulnerability to injection attack with unwashed user input. You're crossing a bright red line whenever you find yourself changing .text() calls to .html() which the literal question implies would have to be done. (Thanks @AlexS for highlighting this point.) Even if you rule out a security risk at the time, future changes could unwittingly introduce it. Instead, this CSS allows you to get hard line breaks without markup using the safer .text().

Difference between "\n" and Environment.NewLine

Environment.NewLine will return the newline character for the corresponding platform in which your code is running

you will find this very useful when you deploy your code in linux on the Mono framework

jsPDF multi page PDF with HTML renderer

$( document ).ready(function() {    
$('#cmd').click(function() {
      var options = {
              pagesplit: true //include this in your code
      };
      var pdf = new jsPDF('p', 'pt', 'a4');
      pdf.addHTML($("#pdfContent"), 15, 15, options, function() {
        pdf.save('Menu.pdf');
      });
    });
});

CSS: How to have position:absolute div inside a position:relative div not be cropped by an overflow:hidden on a container

I don't really see a way to do this as-is. I think you might need to remove the overflow:hidden from div#1 and add another div within div#1 (ie as a sibling to div#2) to hold your unspecified 'content' and add the overflow:hidden to that instead. I don't think that overflow can be (or should be able to be) over-ridden.

Delete all but the most recent X files in bash

I needed an elegant solution for the busybox (router), all xargs or array solutions were useless to me - no such command available there. find and mtime is not the proper answer as we are talking about 10 items and not necessarily 10 days. Espo's answer was the shortest and cleanest and likely the most unversal one.

Error with spaces and when no files are to be deleted are both simply solved the standard way:

rm "$(ls -td *.tar | awk 'NR>7')" 2>&-

Bit more educational version: We can do it all if we use awk differently. Normally, I use this method to pass (return) variables from the awk to the sh. As we read all the time that can not be done, I beg to differ: here is the method.

Example for .tar files with no problem regarding the spaces in the filename. To test, replace "rm" with the "ls".

eval $(ls -td *.tar | awk 'NR>7 { print "rm \"" $0 "\""}')

Explanation:

ls -td *.tar lists all .tar files sorted by the time. To apply to all the files in the current folder, remove the "d *.tar" part

awk 'NR>7... skips the first 7 lines

print "rm \"" $0 "\"" constructs a line: rm "file name"

eval executes it

Since we are using rm, I would not use the above command in a script! Wiser usage is:

(cd /FolderToDeleteWithin && eval $(ls -td *.tar | awk 'NR>7 { print "rm \"" $0 "\""}'))

In the case of using ls -t command will not do any harm on such silly examples as: touch 'foo " bar' and touch 'hello * world'. Not that we ever create files with such names in real life!

Sidenote. If we wanted to pass a variable to the sh this way, we would simply modify the print (simple form, no spaces tolerated):

print "VarName="$1

to set the variable VarName to the value of $1. Multiple variables can be created in one go. This VarName becomes a normal sh variable and can be normally used in a script or shell afterwards. So, to create variables with awk and give them back to the shell:

eval $(ls -td *.tar | awk 'NR>7 { print "VarName=\""$1"\""  }'); echo "$VarName"

Converting RGB to grayscale/intensity

Heres some code in c to convert rgb to grayscale. The real weighting used for rgb to grayscale conversion is 0.3R+0.6G+0.11B. these weights arent absolutely critical so you can play with them. I have made them 0.25R+ 0.5G+0.25B. It produces a slightly darker image.

NOTE: The following code assumes xRGB 32bit pixel format

unsigned int *pntrBWImage=(unsigned int*)..data pointer..;  //assumes 4*width*height bytes with 32 bits i.e. 4 bytes per pixel
unsigned int fourBytes;
        unsigned char r,g,b;
        for (int index=0;index<width*height;index++)
        {
            fourBytes=pntrBWImage[index];//caches 4 bytes at a time
            r=(fourBytes>>16);
            g=(fourBytes>>8);
            b=fourBytes;

            I_Out[index] = (r >>2)+ (g>>1) + (b>>2); //This runs in 0.00065s on my pc and produces slightly darker results
            //I_Out[index]=((unsigned int)(r+g+b))/3;     //This runs in 0.0011s on my pc and produces a pure average
        }

jQuery click event not working after adding class

on document ready event there is no a tag with class tabclick. so you have to bind click event dynamically when you are adding tabclick class. please this code:

$("a.applicationdata").click(function() {
    var appid = $(this).attr("id");

   $('#gentab a').addClass("tabclick")
    .click(function() {
          var liId = $(this).parent("li").attr("id");
         alert(liId);        
      });


 $('#gentab a').attr('href', '#datacollector');

});

How do I make WRAP_CONTENT work on a RecyclerView

Simply put your RecyclerView inside a NestedScrollView. Works perfectly

<android.support.v4.widget.NestedScrollView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="10dp"
                android:layout_marginBottom="25dp">
                <android.support.v7.widget.RecyclerView
                    android:id="@+id/kliste"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent" />
            </android.support.v4.widget.NestedScrollView>

How to Test Facebook Connect Locally

It's simple enough when you find out.

Open /etc/hosts (unix) or C:\WINDOWS\system32\drivers\etc\hosts.

If your domain is foo.com, then add this line:

127.0.0.1    local.foo.com

When you are testing, open local.foo.com in your browser and it should work.

How to check if a file exists in a folder?

This helped me:

bool fileExists = (System.IO.File.Exists(filePath) ? true : false);

How to match letters only using java regex, matches method?

"[a-zA-Z]" matches only one character. To match multiple characters, use "[a-zA-Z]+".

Since a dot is a joker for any character, you have to mask it: "abc\." To make the dot optional, you need a question mark: "abc\.?"

If you write the Pattern as literal constant in your code, you have to mask the backslash:

System.out.println ("abc".matches ("abc\\.?"));
System.out.println ("abc.".matches ("abc\\.?"));
System.out.println ("abc..".matches ("abc\\.?"));

Combining both patterns:

System.out.println ("abc.".matches ("[a-zA-Z]+\\.?"));

Instead of a-zA-Z, \w is often more appropriate, since it captures foreign characters like äöüßø and so on:

System.out.println ("abc.".matches ("\\w+\\.?"));   

MVC Form not able to post List of objects

Please read this: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx
You should set indicies for your html elements "name" attributes like planCompareViewModel[0].PlanId, planCompareViewModel[1].PlanId to make binder able to parse them into IEnumerable.
Instead of @foreach (var planVM in Model) use for loop and render names with indexes.

how to download file using AngularJS and calling MVC API?

The solution by tremendows worked well for me. However , file was not getting saved in Internet Explorer 10+ also. The below code worked for me for IE browser.

var file = new Blob(([data]), { type: 'application/pdf' });
if (window.navigator.msSaveOrOpenBlob) {
    navigator.msSaveBlob(file, 'fileName.pdf');
}

How to find/identify large commits in git history?

I stumbled across this for the same reason as anyone else. But the quoted scripts didn't quite work for me. I've made one that is more a hybrid of those I've seen and it now lives here - https://gitlab.com/inorton/git-size-calc

Reshaping data.frame from wide to long format

reshape() takes a while to get used to, just as melt/cast. Here is a solution with reshape, assuming your data frame is called d:

reshape(d, 
        direction = "long",
        varying = list(names(d)[3:7]),
        v.names = "Value",
        idvar = c("Code", "Country"),
        timevar = "Year",
        times = 1950:1954)

How do I print part of a rendered HTML page in JavaScript?

Along the same lines as some of the suggestions you would need to do at least the following:

  • Load some CSS dynamically through JavaScript
  • Craft some print-specific CSS rules
  • Apply your fancy CSS rules through JavaScript

An example CSS could be as simple as this:

@media print {
  body * {
    display:none;
  }

  body .printable {
    display:block;
  }
}

Your JavaScript would then only need to apply the "printable" class to your target div and it will be the only thing visible (as long as there are no other conflicting CSS rules -- a separate exercise) when printing happens.

<script type="text/javascript">
  function divPrint() {
    // Some logic determines which div should be printed...
    // This example uses div3.
    $("#div3").addClass("printable");
    window.print();
  }
</script>

You may want to optionally remove the class from the target after printing has occurred, and / or remove the dynamically-added CSS after printing has occurred.

Below is a full working example, the only difference is that the print CSS is not loaded dynamically. If you want it to really be unobtrusive then you will need to load the CSS dynamically like in this answer.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
  <head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8" />
    <title>Print Portion Example</title>
    <style type="text/css">
      @media print {
        body * {
          display:none;
        }

        body .printable {
          display:block;
        }
      }
    </style>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
  </head>

  <body>
    <h1>Print Section Example</h1>
    <div id="div1">Div 1</div>
    <div id="div2">Div 2</div>
    <div id="div3">Div 3</div>
    <div id="div4">Div 4</div>
    <div id="div5">Div 5</div>
    <div id="div6">Div 6</div>
    <p><input id="btnSubmit" type="submit" value="Print" onclick="divPrint();" /></p>
    <script type="text/javascript">
      function divPrint() {
        // Some logic determines which div should be printed...
        // This example uses div3.
        $("#div3").addClass("printable");
        window.print();
      }
    </script>
  </body>
</html>

grep a file, but show several surrounding lines?

Search for "17655" in "/some/file.txt" showing 10 lines context before and after (using Awk), output preceded with line number followed by a colon. Use this on Solaris when 'grep' does not support the "-[ACB]" options.

awk '

/17655/ {
        for (i = (b + 1) % 10; i != b; i = (i + 1) % 10) {
                print before[i]
        }
        print (NR ":" ($0))
        a = 10
}

a-- > 0 {
        print (NR ":" ($0))
}

{
        before[b] = (NR ":" ($0))
        b = (b + 1) % 10
}' /some/file.txt;

Checking for directory and file write permissions in .NET

Directory.GetAccessControl(path) does what you are asking for.

public static bool HasWritePermissionOnDir(string path)
{
    var writeAllow = false;
    var writeDeny = false;
    var accessControlList = Directory.GetAccessControl(path);
    if (accessControlList == null)
        return false;
    var accessRules = accessControlList.GetAccessRules(true, true, 
                                typeof(System.Security.Principal.SecurityIdentifier));
    if (accessRules ==null)
        return false;

    foreach (FileSystemAccessRule rule in accessRules)
    {
        if ((FileSystemRights.Write & rule.FileSystemRights) != FileSystemRights.Write) 
            continue;

        if (rule.AccessControlType == AccessControlType.Allow)
            writeAllow = true;
        else if (rule.AccessControlType == AccessControlType.Deny)
            writeDeny = true;
    }

    return writeAllow && !writeDeny;
}

(FileSystemRights.Write & rights) == FileSystemRights.Write is using something called "Flags" btw which if you don't know what it is you should really read up on :)

How to execute a function when page has fully loaded?

If you need to use many onload use $(window).load instead (jQuery):

$(window).load(function() {
    //code
});

querySelector, wildcard element match?

[id^='someId'] will match all ids starting with someId.

[id$='someId'] will match all ids ending with someId.

[id*='someId'] will match all ids containing someId.

If you're looking for the name attribute just substitute id with name.

If you're talking about the tag name of the element I don't believe there is a way using querySelector

How can I print each command before executing?

The easiest way to do this is to let bash do it:

set -x

Or run it explicitly as bash -x myscript.

How can I delay a method call for 1 second?

You can do this

[self performSelector:@selector(MethodToExecute) withObject:nil afterDelay:1.0 ];

trying to align html button at the center of the my page

Here's your solution: JsFiddle

Basically, place your button into a div with centred text:

<div class="wrapper">
    <button class="button">Button</button>
</div>

With the following styles:

.wrapper {
    text-align: center;
}

.button {
    position: absolute;
    top: 50%;
}

There are many ways to skin a cat, and this is just one.

Unix ls command: show full path when using options

What about this trick...

ls -lrt -d -1 $PWD/{*,.*}

OR

ls -lrt -d -1 $PWD/*

I think this has problems with empty directories but if another poster has a tweak I'll update my answer. Also, you may already know this but this is probably be a good candidate for an alias given it's lengthiness.

[update] added some tweaks based on comments, thanks guys.

[update] as pointed out by the comments you may need to tweek the matcher expressions depending on the shell (bash vs zsh). I've re-added my older command for reference.

Jquery Open in new Tab (_blank)

window.location always refers to the location of the current window. Changing it will affect only the current window.

One thing that can be done is forcing a click on the link after setting its target attribute to _blank:

Check this: http://www.techfoobar.com/2012/jquery-programmatically-clicking-a-link-and-forcing-the-default-action

Disclaimer: Its my blog.

Convert JSON to Map

Using the GSON library:

import com.google.gson.Gson;
import com.google.common.reflect.TypeToken;
import java.lang.reclect.Type;

Use the following code:

Type mapType = new TypeToken<Map<String, Map>>(){}.getType();  
Map<String, String[]> son = new Gson().fromJson(easyString, mapType);

Fetch: POST json data

I think that, we don't need parse the JSON object into a string, if the remote server accepts json into they request, just run:

const request = await fetch ('/echo/json', {
  headers: {
    'Content-type': 'application/json'
  },
  method: 'POST',
  body: { a: 1, b: 2 }
});

Such as the curl request

curl -v -X POST -H 'Content-Type: application/json' -d '@data.json' '/echo/json'

In case to the remote serve not accept a json file as the body, just send a dataForm:

const data =  new FormData ();
data.append ('a', 1);
data.append ('b', 2);

const request = await fetch ('/echo/form', {
  headers: {
    'Content-type': 'application/x-www-form-urlencoded'
  },
  method: 'POST',
  body: data
});

Such as the curl request

curl -v -X POST -H 'Content-type: application/x-www-form-urlencoded' -d '@data.txt' '/echo/form'

SQL Server IF EXISTS THEN 1 ELSE 2

In SQL without SELECT you cannot result anything. Instead of IF-ELSE block I prefer to use CASE statement for this

SELECT CASE
         WHEN EXISTS (SELECT 1
                      FROM   tblGLUserAccess
                      WHERE  GLUserName = 'xxxxxxxx') THEN 1
         ELSE 2
       END 

What is @ModelAttribute in Spring MVC?

I know this is an old thread, but I thought I throw my hat in the ring and see if I can muddy the water a little bit more :)

I found my initial struggle to understand @ModelAttribute was a result of Spring's decision to combine several annotations into one. It became clearer once I split it into several smaller annotations:

For parameter annotations, think of @ModelAttribute as the equivalent of @Autowired + @Qualifier i.e. it tries to retrieve a bean with the given name from the Spring managed model. If the named bean is not found, instead of throwing an error or returning null, it implicitly takes on the role of @Bean i.e. Create a new instance using the default constructor and add the bean to the model.

For method annotations, think of @ModelAttribute as the equivalent of @Bean + @Before, i.e. it puts the bean constructed by user's code in the model and it's always called before a request handling method.

Figuratively, I see @ModelAttribute as the following (please don't take it literally!!):

@Bean("person")
@Before
public Person createPerson(){
  return new Person();
}

@RequestMapping(...)
public xxx handlePersonRequest( (@Autowired @Qualifier("person") | @Bean("person")) Person person, xxx){
  ...
}

As you can see, Spring made the right decision to make @ModelAttribute an all-encompassing annotation; no one wants to see an annotation smorgasbord.

C# how to create a Guid value?

There's also ShortGuid - A shorter and url friendly GUID class in C#. It's available as a Nuget. More information here.

PM> Install-Package CSharpVitamins.ShortGuid

Usage:

Guid guid = Guid.NewGuid();
ShortGuid sguid1 = guid; // implicitly cast the guid as a shortguid
Console.WriteLine(sguid1);
Console.WriteLine(sguid1.Guid);

This produces a new guid, uses that guid to create a ShortGuid, and displays the two equivalent values in the console. Results would be something along the lines of:

ShortGuid: FEx1sZbSD0ugmgMAF_RGHw 
Guid:      b1754c14-d296-4b0f-a09a-030017f4461f

Forward declaring an enum in C++

Just noting that the reason actually is that the size of the enum is not yet known after forward declaration. Well, you use forward declaration of a struct to be able to pass a pointer around or refer to an object from a place that's refered to in the forward declared struct definition itself too.

Forward declaring an enum would not be too useful, because one would wish to be able to pass around the enum by-value. You couldn't even have a pointer to it, because i recently got told some platforms use pointers of different size for char than for int or long. So it all depends on the content of the enum.

The current C++ Standard explicitly disallows doing something like

enum X;

(in 7.1.5.3/1). But the next C++ Standard due to next year allows the following, which convinced me the problem actually has to do with the underlying type:

enum X : int;

It's known as a "opaque" enum declaration. You can even use X by value in the following code. And its enumerators can later be defined in a later redeclaration of the enumeration. See 7.2 in the current working draft.

Dynamically add child components in React

You need to pass your components as children, like this:

var App = require('./App.js');
var SampleComponent = require('./SampleComponent.js');
ReactDOM.render(
    <App>
        <SampleComponent name="SomeName"/> 
    <App>, 
    document.body
);

And then append them in the component's body:

var App = React.createClass({
    render: function() {
        return (
            <div>
                <h1>App main component! </h1>
                {
                    this.props.children
                }
            </div>
        );
    }
});

You don't need to manually manipulate HTML code, React will do that for you. If you want to add some child components, you just need to change props or state it depends. For example:

var App = React.createClass({

    getInitialState: function(){
        return [
            {id:1,name:"Some Name"}
        ]
    },

    addChild: function() {
        // State change will cause component re-render
        this.setState(this.state.concat([
            {id:2,name:"Another Name"}
        ]))
    }

    render: function() {
        return (
            <div>
                <h1>App main component! </h1>
                <button onClick={this.addChild}>Add component</button>
                {
                    this.state.map((item) => (
                        <SampleComponent key={item.id} name={item.name}/>
                    ))
                }
            </div>
        );
    }

});

Apache server keeps crashing, "caught SIGTERM, shutting down"

I had mysterious SIGTERM shutdowns in our L.A.M.P. server, and it turned out to be an error in a custom PHP module, which was caused by mismatched versions. It was found by looking in the apache access/error logs at the time of malfunction. Don't forget to turn error logging on.

Value cannot be null. Parameter name: source

It could be as silly as in my case where savechanges was erroring bcoz the db did not have foreign keys and associations were added to EDM tables. I added foreign keys in the db and regenerated EDM for a fix.

The errors I was seeing are as follows: Case 1 -> when using DBContext for EDM Message=Value cannot be null. Parameter name: source at System.Linq.Enumerable.Any[TSource](IEnumerable1 source, Func2 predicate)

Case 2 -> when using ObjectContext for EDM Message=Unable to update the EntitySet 'Contact' because it has a DefiningQuery and no element exists in the element to support the current operation.

(Just wanted to throw it in there in case it helps someone).

Boolean checking in the 'if' condition

This is more readable and good practice too.

if(!status){
//do sth
}else{
//do sth
}

Download pdf file using jquery ajax

For those looking a more modern approach, you can use the fetch API. The following example shows how to download a PDF file. It is easily done with the following code.

fetch(url, {
    body: JSON.stringify(data),
    method: 'POST',
    headers: {
        'Content-Type': 'application/json; charset=utf-8'
    },
})
.then(response => response.blob())
.then(response => {
    const blob = new Blob([response], {type: 'application/pdf'});
    const downloadUrl = URL.createObjectURL(blob);
    const a = document.createElement("a");
    a.href = downloadUrl;
    a.download = "file.pdf";
    document.body.appendChild(a);
    a.click();
})

I believe this approach to be much easier to understand than other XMLHttpRequest solutions. Also, it has a similar syntax to the jQuery approach, without the need to add any additional libraries.

Of course, I would advise checking to which browser you are developing, since this new approach won't work on IE. You can find the full browser compatibility list on the following [link][1].

Important: In this example I am sending a JSON request to a server listening on the given url. This url must be set, on my example I am assuming you know this part. Also, consider the headers needed for your request to work. Since I am sending a JSON, I must add the Content-Type header and set it to application/json; charset=utf-8, as to let the server know the type of request it will receive.

gcloud command not found - while installing Google Cloud SDK

How to install GCloud and Always Works after Restart On Mac OS HIGH Sierra:

  1. Download install package Here

  2. Achieved file and drop in your folder

  3. Open terminal, go to your folder with file and enter this command:

     ./google-cloud-sdk/install.sh
    
  4. "Modify profile to update your $PATH and enable bash completion?"
    Yes

  5. Enter this path to modify:
    /Users/USERNAME_COMPUTER/.bashrc
  6. After all install, enter this:

      source ~/.bashrc
    
  7. Enter this to check install gcloud:

    gcloud - -version

  8. Open new window terminal cmd+n DONT CLOSE OLD WINDOW and enter in new window gcloud version

    if: «command not found» go to step 9

    else: Congratulations GCloud work in terminal

  9. Return to old window and enter echo $PATH and copy path to GCloud

  10. Open BASH_PROFILE:

    open ~/.bash_profile
    
  11. Enter path to new Bash:

    « export PATH="/Users/USERNAME_COMPUTER/google-cloud-sdk/bin:$PATH" »
    
  12. Return to step 8

How to upgrade Git to latest version on macOS?

I used the following to upgrade git on mac.

hansi$ brew install git 

hansi$ git --version 
git version 2.19.0


hansi$ brew install git
Warning: git 2.25.1 is already installed, it's just not linked
You can use `brew link git` to link this version.

hansi$ brew link git 
Linking /usr/local/Cellar/git/2.25.1... 
Error: Could not symlink bin/git
Target /usr/local/bin/git
already exists. You may want to remove it:
  rm '/usr/local/bin/git'

To force the link and overwrite all conflicting files:
  brew link --overwrite git

To list all files that would be deleted:
  brew link --overwrite --dry-run git

hansi$ brew link --overwrite git 
Linking /usr/local/Cellar/git/2.25.1... 205 symlinks created


hansi$ git --version
git version 2.25.1

Telegram Bot - how to get a group chat id?

You can get Chat ID in this way.

On private chat with your bot, send a random message. You will search this message later.

Get Your API-token from bot_father : XXXXXXXXX:YYYYYYY-YYYYYYYYYYYYYYYYY_YY

Then, on your browser make a request with that url :

https://api.telegram.org/botXXXXXXXXX:YYYYYYY-YYYYYYYYYYYYYYYYY_YY/getUpdates

The request returns a json response, in json text search your random message and get chat id in that object.

What is “assert” in JavaScript?

If you use webpack, you can just use the node.js assertion library. Although they claim that it's "not intended to be a general purpose assertion library", it seems to be more than OK for ad hoc assertions, and it seems no competitor exists in the Node space anyway (Chai is designed for unit testing).

const assert = require('assert');
...
assert(jqXHR.status == 201, "create response should be 201");

You need to use webpack or browserify to be able to use this, so obviously this is only useful if those are already in your workflow.

How do I free my port 80 on localhost Windows?

Other option to try is to stop SQL Server Reporting Services.

Key Shortcut for Eclipse Imports

CTRL + 1 can also be used which will suggest to import.

Display string multiple times

The accepted answer is short and sweet, but here is an alternate syntax allowing to provide a separator in Python 3.x.

print(*3*('-',), sep='_')

UnmodifiableMap (Java Collections) vs ImmutableMap (Google)

An unmodifiable map may still change. It is only a view on a modifiable map, and changes in the backing map will be visible through the unmodifiable map. The unmodifiable map only prevents modifications for those who only have the reference to the unmodifiable view:

Map<String, String> realMap = new HashMap<String, String>();
realMap.put("A", "B");

Map<String, String> unmodifiableMap = Collections.unmodifiableMap(realMap);

// This is not possible: It would throw an 
// UnsupportedOperationException
//unmodifiableMap.put("C", "D");

// This is still possible:
realMap.put("E", "F");

// The change in the "realMap" is now also visible
// in the "unmodifiableMap". So the unmodifiableMap
// has changed after it has been created.
unmodifiableMap.get("E"); // Will return "F". 

In contrast to that, the ImmutableMap of Guava is really immutable: It is a true copy of a given map, and nobody may modify this ImmutableMap in any way.

Update:

As pointed out in a comment, an immutable map can also be created with the standard API using

Map<String, String> immutableMap = 
    Collections.unmodifiableMap(new LinkedHashMap<String, String>(realMap)); 

This will create an unmodifiable view on a true copy of the given map, and thus nicely emulates the characteristics of the ImmutableMap without having to add the dependency to Guava.

Running stages in parallel with Jenkins workflow / pipeline

You may not place the deprecated non-block-scoped stage (as in the original question) inside parallel.

As of JENKINS-26107, stage takes a block argument. You may put parallel inside stage or stage inside parallel or stage inside stage etc. However visualizations of the build are not guaranteed to support all nestings; in particular

  • The built-in Pipeline Steps (a “tree table” listing every step run by the build) shows arbitrary stage nesting.
  • The Pipeline Stage View plugin will currently only display a linear list of stages, in the order they started, regardless of nesting structure.
  • Blue Ocean will display top-level stages, plus parallel branches inside a top-level stage, but currently no more.

JENKINS-27394, if implemented, would display arbitrarily nested stages.

Retrieve a single file from a repository

I solved in this way:

git archive --remote=ssh://[email protected]/user/mi-repo.git BranchName /path-to-file/file_name | tar -xO /path-to-file/file_name > /path-to-save-the-file/file_name

If you want, you could replace "BranchName" for "HEAD"

Servlet returns "HTTP Status 404 The requested resource (/servlet) is not available"

Please check context root cannot be empty.

If you're using eclipse:
right click, select properties, then web project settings. Check the context root cannot be empty

get keys of json-object in JavaScript

var jsonData = [{"person":"me","age":"30"},{"person":"you","age":"25"}];

for(var i in jsonData){
    var key = i;
    var val = jsonData[i];
    for(var j in val){
        var sub_key = j;
        var sub_val = val[j];
        console.log(sub_key);
    }
}

EDIT

var jsonObj = {"person":"me","age":"30"};
Object.keys(jsonObj);  // returns ["person", "age"]

Object has a property keys, returns an Array of keys from that Object

Chrome, FF & Safari supports Object.keys

receiving json and deserializing as List of object at spring mvc controller

Solution works very well,

public List<String> savePerson(@RequestBody Person[] personArray)  

For this signature you can pass Person array from postman like

[
{
  "empId": "10001",
  "tier": "Single",
  "someting": 6,
  "anything": 0,
  "frequency": "Quaterly"
}, {
  "empId": "10001",
  "tier": "Single",
  "someting": 6,
  "anything": 0,
  "frequency": "Quaterly"
}
]

Don't forget to add consumes tag:

@RequestMapping(value = "/getEmployeeList", method = RequestMethod.POST, consumes="application/json", produces = "application/json")
public List<Employee> getEmployeeDataList(@RequestBody Employee[] employeearray) { ... }

Try catch statements in C

In C99, you can use setjmp/longjmp for non-local control flow.

Within a single scope, the generic, structured coding pattern for C in the presence of multiple resource allocations and multiple exits uses goto, like in this example. This is similar to how C++ implements destructor calls of automatic objects under the hood, and if you stick to this diligently, it should allow you for a certain degree of cleanness even in complex functions.

Read input from console in Ruby?

If you want to make interactive console:

#!/usr/bin/env ruby

require "readline"
addends = []
while addend_string = Readline.readline("> ", true)
  addends << addend_string.to_i
  puts "#{addends.join(' + ')} = #{addends.sum}"
end

Usage (assuming you put above snippet into summator file in current directory):

chmod +x summator
./summator
> 1
1 = 1
> 2
1 + 2 = 3

Use Ctrl + D to exit

How to create cron job using PHP?

That may depend on your web host if you are not hosting your own content. If your web host supports creating chron jobs, they may have a form for you to fill out that lets you select the frequency and input the absolute path to the file to execute. For instance, my web host (DreamHost) allows me to create custom cron jobs by typing in the absolute path to the file and selecting the frequency from a select menu. This may not be possible for your server, in which case you need to either edit the crontab directly or through your host specific method.

As Alister Bulman details above, create a PHP file to run using CLI (making sure to include #!/usr/bin/env php at the very start of the file before the <?php tag. This ensures that the shell knows which executable should be invoked when running the script.

How do I enable php to work with postgresql?

You need to install the pgsql module for php. In debian/ubuntu is something like this:

sudo apt-get install php5-pgsql

Or if the package is installed, you need to enable de module in php.ini

extension=php_pgsql.dll (windows)
extension=php_pgsql.so (linux)

Greatings.

How can I stop float left?

Okay I just realized the answer is to remove the first float left from the first DIV. Don't know why I didn't see that before.

Difference between "or" and || in Ruby?

As the others have already explained, the only difference is the precedence. However, I would like to point out that there are actually two differences between the two:

  1. and, or and not have much lower precedence than &&, || and !
  2. and and or have the same precedence, while && has higher precedence than ||

In general, it is good style to avoid the use of and, or and not and use &&, || and ! instead. (The Rails core developers, for example, reject patches which use the keyword forms instead of the operator forms.)

The reason why they exist at all, is not for boolean formulae but for control flow. They made their way into Ruby via Perl's well-known do_this or do_that idiom, where do_this returns false or nil if there is an error and only then is do_that executed instead. (Analogous, there is also the do_this and then_do_that idiom.)

Examples:

download_file_via_fast_connection or download_via_slow_connection
download_latest_currency_rates and store_them_in_the_cache

Sometimes, this can make control flow a little bit more fluent than using if or unless.

It's easy to see why in this case the operators have the "wrong" (i.e. identical) precedence: they never show up together in the same expression anyway. And when they do show up together, you generally want them to be evaluated simply left-to-right.

Insert at first position of a list in Python

From the documentation:

list.insert(i, x)
Insert an item at a given position. The first argument is the index of the element before which to insert, so a.insert(0, x) inserts at the front of the list, and a.insert(len(a),x) is equivalent to a.append(x)

http://docs.python.org/2/tutorial/datastructures.html#more-on-lists

Insert/Update Many to Many Entity Framework . How do I do it?

I wanted to add my experience on that. Indeed EF, when you add an object to the context, it changes the state of all the children and related entities to Added. Although there is a small exception in the rule here: if the children/related entities are being tracked by the same context, EF does understand that these entities exist and doesn't add them. The problem happens when for example, you load the children/related entities from some other context or a web ui etc and then yes, EF doesn't know anything about these entities and goes and adds all of them. To avoid that, just get the keys of the entities and find them (e.g. context.Students.FirstOrDefault(s => s.Name == "Alice")) in the same context in which you want to do the addition.

How to calculate percentage with a SQL statement

I simply use this when ever I need to work out a percentage..

ROUND(CAST((Numerator * 100.0 / Denominator) AS FLOAT), 2) AS Percentage

Note that 100.0 returns decimals, whereas 100 on it's own will round up the result to the nearest whole number, even with the ROUND() function!

Matrix multiplication in OpenCV

You say that the matrices are the same dimensions, and yet you are trying to perform matrix multiplication on them. Multiplication of matrices with the same dimension is only possible if they are square. In your case, you get an assertion error, because the dimensions are not square. You have to be careful when multiplying matrices, as there are two possible meanings of multiply.

Matrix multiplication is where two matrices are multiplied directly. This operation multiplies matrix A of size [a x b] with matrix B of size [b x c] to produce matrix C of size [a x c]. In OpenCV it is achieved using the simple * operator:

C = A * B

Element-wise multiplication is where each pixel in the output matrix is formed by multiplying that pixel in matrix A by its corresponding entry in matrix B. The input matrices should be the same size, and the output will be the same size as well. This is achieved using the mul() function:

output = A.mul(B);

How to construct a set out of list items in python?

Simply put the line:

new_list = set(your_list)

CSS :not(:last-child):after selector

Your example as written works perfectly in Chrome 11 for me. Perhaps your browser just doesn't support the :not() selector?

You may need to use JavaScript or similar to accomplish this cross-browser. jQuery implements :not() in its selector API.

Redirect echo output in shell script to logfile

#!/bin/sh
# http://www.tldp.org/LDP/abs/html/io-redirection.html
echo "Hello World"
exec > script.log 2>&1
echo "Start logging out from here to a file"
bad command
echo "End logging out from here to a file"
exec > /dev/tty 2>&1 #redirects out to controlling terminal
echo "Logged in the terminal"

Output:

> ./above_script.sh                                                                
Hello World
Not logged in the file
> cat script.log
Start logging out from here to a file
./logging_sample.sh: line 6: bad: command not found
End logging out from here to a file

Read more here: http://www.tldp.org/LDP/abs/html/io-redirection.html

What possibilities can cause "Service Unavailable 503" error?

If the server doesn't have enough memory also will cause this problem. This is my personal experience with Godaddy VPS.

Python and JSON - TypeError list indices must be integers not str

First of all, you should be using json.loads, not json.dumps. loads converts JSON source text to a Python value, while dumps goes the other way.

After you fix that, based on the JSON snippet at the top of your question, readable_json will be a list, and so readable_json['firstName'] is meaningless. The correct way to get the 'firstName' field of every element of a list is to eliminate the playerstuff = readable_json['firstName'] line and change for i in playerstuff: to for i in readable_json:.

Javascript/jQuery: Set Values (Selection) in a multiple Select

in jQuery:

$("#strings").val(["Test", "Prof", "Off"]);

or in pure JavaScript:

var element = document.getElementById('strings');
var values = ["Test", "Prof", "Off"];
for (var i = 0; i < element.options.length; i++) {
    element.options[i].selected = values.indexOf(element.options[i].value) >= 0;
}

jQuery does significant abstraction here.

What's the difference between getRequestURI and getPathInfo methods in HttpServletRequest?

getPathInfo() gives the extra path information after the URI, used to access your Servlet, where as getRequestURI() gives the complete URI.

I would have thought they would be different, given a Servlet must be configured with its own URI pattern in the first place; I don't think I've ever served a Servlet from root (/).

For example if Servlet 'Foo' is mapped to URI '/foo' then I would have thought the URI:

/foo/path/to/resource

Would result in:

RequestURI = /foo/path/to/resource

and

PathInfo = /path/to/resource

Cannot read property 'length' of null (javascript)

From the code that you have provided, not knowing the language that you are programming in. The variable capital is null. When you are trying to read the property length, the system cant as it is trying to deference a null variable. You need to define capital.

What good technology podcasts are out there?

I've been listening to Tanked Podcast. It's three friends that hang out and talk about tech, movies, video games, and they talk about the odd stuff that happens every week on the web. These guys are a blast and have way to much fun!

Check if table exists

If using jruby, here is a code snippet to return an array of all tables in a db.

require "rubygems"
require "jdbc/mysql"
Jdbc::MySQL.load_driver
require "java"

def get_database_tables(connection, db_name)
  md = connection.get_meta_data
  rs = md.get_tables(db_name, nil, '%',["TABLE"])

  tables = []
  count = 0
  while rs.next
    tables << rs.get_string(3)
  end #while
  return tables
end

What is simplest way to read a file into String?

From Java 7 (API Description) onwards you can do:

new String(Files.readAllBytes(Paths.get(filePath)), StandardCharsets.UTF_8);

Where filePath is a String representing the file you want to load.

How do I grant myself admin access to a local SQL Server instance?

Open a command prompt window. If you have a default instance of SQL Server already running, run the following command on the command prompt to stop the SQL Server service:

net stop mssqlserver

Now go to the directory where SQL server is installed. The directory can for instance be one of these:

C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Binn
C:\Program Files\Microsoft SQL Server\MSSQL13.MSSQLSERVER\MSSQL\Binn

Figure out your MSSQL directory and CD into it as such:

CD C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Binn

Now run the following command to start SQL Server in single user mode. As SQLCMD is being specified, only one SQLCMD connection can be made (from another command prompt window).

sqlservr -m"SQLCMD"

Now, open another command prompt window as the same user as the one that started SQL Server in single user mode above, and in it, run:

sqlcmd

And press enter. Now you can execute SQL statements against the SQL Server instance running in single user mode:

create login [<<DOMAIN\USERNAME>>] from windows;

-- For older versions of SQL Server:
EXEC sys.sp_addsrvrolemember @loginame = N'<<DOMAIN\USERNAME>>', @rolename = N'sysadmin';

-- For newer versions of SQL Server:
ALTER SERVER ROLE [sysadmin] ADD MEMBER [<<DOMAIN\USERNAME>>];

GO

Source.

UPDATED Do not forget a semicolon after ALTER SERVER ROLE [sysadmin] ADD MEMBER [<<DOMAIN\USERNAME>>]; and do not add extra semicolon after GO or the command never executes.

Remove/ truncate leading zeros by javascript/jquery

parseInt(value) or parseFloat(value)

This will work nicely.

Hashmap does not work with int, char

Generics can be defined using Wrapper classes only. If you don't want to define using Wrapper types, you may use the Raw definition as below

@SuppressWarnings("rawtypes")
public HashMap buildMap(String letters)
{
    HashMap checkSum = new HashMap();

    for ( int i = 0; i < letters.length(); ++i )
    {
       checkSum.put(letters.charAt(i), primes[i]);
    }
    return checkSum;
}

Or define the HashMap using wrapper types, and store the primitive types. The primitive values will be promoted to their wrapper types.

public HashMap<Character, Integer> buildMap(String letters)
{
  HashMap<Character, Integer> checkSum = new HashMap<Character, Integer>();

  for ( int i = 0; i < letters.length(); ++i )
  {
    checkSum.put(letters.charAt(i), primes[i]);
  }
  return checkSum;
}

How to compare objects by multiple fields

Its easy to do using Google's Guava library.

e.g. Objects.equal(name, name2) && Objects.equal(age, age2) && ...

More examples:

preg_match in JavaScript?

Sample code to get image links within HTML content. Like preg_match_all in PHP

let HTML = '<div class="imageset"><table><tbody><tr><td width="50%"><img src="htt ps://domain.com/uploads/monthly_2019_11/7/1.png.jpg" class="fr-fic fr-dii"></td><td width="50%"><img src="htt ps://domain.com/uploads/monthly_2019_11/7/9.png.jpg" class="fr-fic fr-dii"></td></tr></tbody></table></div>';
let re = /<img src="(.*?)"/gi;
let result = HTML.match(re);

out array

0: "<img src="htt ps://domain.com/uploads/monthly_2019_11/7/1.png.jpg""
1: "<img src="htt ps://domain.com/uploads/monthly_2019_11/7/9.png.jpg""

Command-line Git on Windows

If you have installed GitHubDesktop in Windows 10, then press Ctrl + '. or in the menu go to Repository>Open in command prompt.

In case git is not installed in your machine, you should get a prompt to install git.(I came to know from this that GitHubDesktop and git are different applications). Install git, close your command prompt and open it again.

You can test your installation by typing in git at the command prompt.