Correct redirect URI for Google API and OAuth 2.0
There's no problem with using a localhost url for Dev work - obviously it needs to be changed when it comes to production.
You need to go here:
https://developers.google.com/accounts/docs/OAuth2
and then follow the link for the API Console - link's in the Basic Steps section. When you've filled out the new application form you'll be asked to provide a redirect Url. Put in the page you want to go to once access has been granted.
When forming the Google oAuth Url - you need to include the redirect url - it has to be an exact match or you'll have problems. It also needs to be UrlEncoded.
JWT (Json Web Token) Audience "aud" versus Client_Id - What's the difference?
Though this is old, I think question is valid even today
My suspicion is that aud should refer to the resource server(s), and
the client_id should refer to one of the client applications
recognized by the authentication server
Yes, aud should refer to token consuming party. And client_id refers to token obtaining party.
In my current case, my resource server is also my web app client.
In the OP's scenario, web app and resource server both belongs to same party. So this means client and audience to be same. But there can be situations where this is not the case.
Think about a SPA which consume an OAuth protected resource. In this scenario SPA is the client. Protected resource is the audience of access token.
This second scenario is interesting. There is a working draft in place named "Resource Indicators for OAuth 2.0" which explain where you can define the intended audience in your authorisation request. So the resulting token will restricted to the specified audience. Also, Azure OIDC use a similar approach where it allows resource registration and allow auth request to contain resource parameter to define access token intended audience. Such mechanisms allow OAuth adpotations to have a separation between client and token consuming (audience) party.
OAuth 2.0 Authorization Header
For those looking for an example of how to pass the OAuth2 authorization (access token) in the header (as opposed to using a request or body parameter), here is how it's done:
Authorization: Bearer 0b79bab50daca910b000d4f1a2b675d604257e42
OAuth2 and Google API: access token expiration time?
You shouldn't design your application based on specific lifetimes of access tokens. Just assume they are (very) short lived.
However, after a successful completion of the OAuth2 installed application flow, you will get back a refresh token. This refresh token never expires, and you can use it to exchange it for an access token as needed. Save the refresh tokens, and use them to get access tokens on-demand (which should then immediately be used to get access to user data).
EDIT: My comments above notwithstanding, there are two easy ways to get the access token expiration time:
- It is a parameter in the response (
expires_in
)when you exchange your refresh token (using /o/oauth2/token endpoint). More details.
There is also an API that returns the remaining lifetime of the access_token:
https://www.googleapis.com/oauth2/v1/tokeninfo?access_token={accessToken}
This will return a json array that will contain an expires_in
parameter, which is the number of seconds left in the lifetime of the token.
OWIN Security - How to Implement OAuth2 Refresh Tokens
Freddy's answer helped me a lot to get this working. For the sake of completeness here's how you could implement hashing of the token:
private string ComputeHash(Guid input)
{
byte[] source = input.ToByteArray();
var encoder = new SHA256Managed();
byte[] encoded = encoder.ComputeHash(source);
return Convert.ToBase64String(encoded);
}
In CreateAsync
:
var guid = Guid.NewGuid();
...
_refreshTokens.TryAdd(ComputeHash(guid), refreshTokenTicket);
context.SetToken(guid.ToString());
ReceiveAsync
:
public async Task ReceiveAsync(AuthenticationTokenReceiveContext context)
{
Guid token;
if (Guid.TryParse(context.Token, out token))
{
AuthenticationTicket ticket;
if (_refreshTokens.TryRemove(ComputeHash(token), out ticket))
{
context.SetTicket(ticket);
}
}
}
What are the main differences between JWT and OAuth authentication?
Jwt is a strict set of instructions for the issuing and validating of signed access tokens. The tokens contain claims that are used by an app to limit access to a user
OAuth2 on the other hand is not a protocol, its a delegated authorization framework. think very detailed guideline, for letting users and applications authorize specific permissions to other applications in both private and public settings. OpenID Connect which sits on top of OAUTH2 gives you Authentication and Authorization.it details how multiple different roles, users in your system, server side apps like an API, and clients such as websites or native mobile apps, can authenticate with each othe
Note oauth2 can work with jwt , flexible implementation, extandable to different applications
What are Bearer Tokens and token_type in OAuth 2?
From RFC 6750, Section 1.2:
Bearer Token
A security token with the property that any party in possession of the token (a "bearer") can use the token in any way that any other party in possession of it can. Using a bearer token does not require a bearer to prove possession of cryptographic key material (proof-of-possession).
The Bearer Token or Refresh token is created for you by the Authentication server. When a user authenticates your application (client) the authentication server then goes and generates for your a Bearer Token (refresh token) which you can then use to get an access token.
The Bearer Token is normally some kind of cryptic value created by the authentication server, it isn't random it is created based upon the user giving you access and the client your application getting access.
See also: Mozilla MDN Header Information.
Correct way to set Bearer token with CURL
<?php
$curl = curl_init();
curl_setopt_array($curl, array(
CURLOPT_URL => "your api goes here",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 0,
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "GET",
CURLOPT_HTTPHEADER => array(
"Authorization: Bearer eyJ0eciOiJSUzI1NiJ9.eyJMiIsInNjb3BlcyI6W119.K3lW1STQhMdxfAxn00E4WWFA3uN3iIA"
),
));
$response = curl_exec($curl);
$data = json_decode($response, true);
echo $data;
?>
JWT refresh token flow
Below are the steps to do revoke your JWT access token:
- When you do log in, send 2 tokens (Access token, Refresh token) in response to the client.
- The access token will have less expiry time and Refresh will have long expiry time.
- The client (Front end) will store refresh token in his local storage and access token in cookies.
- The client will use an access token for calling APIs. But when it expires, pick the refresh token from local storage and call auth server API to get the new token.
- Your auth server will have an API exposed which will accept refresh token and checks for its validity and return a new access token.
- Once the refresh token is expired, the User will be logged out.
Please let me know if you need more details, I can share the code (Java + Spring boot) as well.
For your questions:
Q1: It's another JWT with fewer claims put in with long expiry time.
Q2: It won't be in a database. The backend will not store anywhere. They will just decrypt the token with private/public key and validate it with its expiry time also.
Q3: Yes, Correct
What's a redirect URI? how does it apply to iOS app for OAuth2.0?
redirected uri is the location where the user will be redirected after successfully login to your app. for example to get access token for your app in facebook you need to subimt redirected uri which is nothing only the app Domain that your provide when you create your facebook app.
How to refresh token with Google API client?
here is the snippet to set token, before that make sure the access type should be set to offline
if (isset($_GET['code'])) {
$client->authenticate();
$_SESSION['access_token'] = $client->getAccessToken();
}
To refresh token
$google_token= json_decode($_SESSION['access_token']);
$client->refreshToken($google_token->refresh_token);
this will refresh your token, you have to update it in session for that you can do
$_SESSION['access_token']= $client->getAccessToken()
How do I get an OAuth 2.0 authentication token in C#
You may use the following code to get the bearer token.
private string GetBearerToken()
{
var client = new RestClient("https://service.endpoint.com");
client.Authenticator = new HttpBasicAuthenticator("abc", "123");
var request = new RestRequest("api/oauth2/token", Method.POST);
request.AddHeader("content-type", "application/json");
request.AddParameter("application/json", "{ \"grant_type\":\"client_credentials\" }",
ParameterType.RequestBody);
var responseJson = _client.Execute(request).Content;
var token = JsonConvert.DeserializeObject<Dictionary<string, object>>(responseJson)["access_token"].ToString();
if(token.Length == 0)
{
throw new AuthenticationException("API authentication failed.");
}
return token;
}
Why do access tokens expire?
It is essentially a security measure. If your app is compromised, the attacker will only have access to the short-lived access token and no way to generate a new one.
Refresh tokens also expire but they are supposed to live much longer than the access token.
How to validate an OAuth 2.0 access token for a resource server?
An update on @Scott T.'s answer: the interface between Resource Server and Authorization Server for token validation was standardized in IETF RFC 7662 in October 2015, see: https://tools.ietf.org/html/rfc7662. A sample validation call would look like:
POST /introspect HTTP/1.1
Host: server.example.com
Accept: application/json
Content-Type: application/x-www-form-urlencoded
Authorization: Bearer 23410913-abewfq.123483
token=2YotnFZFEjr1zCsicMWpAA
and a sample response:
HTTP/1.1 200 OK
Content-Type: application/json
{
"active": true,
"client_id": "l238j323ds-23ij4",
"username": "jdoe",
"scope": "read write dolphin",
"sub": "Z5O3upPC88QrAjx00dis",
"aud": "https://protected.example.net/resource",
"iss": "https://server.example.com/",
"exp": 1419356238,
"iat": 1419350238,
"extension_field": "twenty-seven"
}
Of course adoption by vendors and products will have to happen over time.
Using an authorization header with Fetch in React Native
completed = (id) => {
var details = {
'id': id,
};
var formBody = [];
for (var property in details) {
var encodedKey = encodeURIComponent(property);
var encodedValue = encodeURIComponent(details[property]);
formBody.push(encodedKey + "=" + encodedValue);
}
formBody = formBody.join("&");
fetch(markcompleted, {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/x-www-form-urlencoded'
},
body: formBody
})
.then((response) => response.json())
.then((responseJson) => {
console.log(responseJson, 'res JSON');
if (responseJson.status == "success") {
console.log(this.state);
alert("your todolist is completed!!");
}
})
.catch((error) => {
console.error(error);
});
};
Using Postman to access OAuth 2.0 Google APIs
I figured out that I was not generating Credentials for the right app type.
If you're using Postman to test Google oAuth 2 APIs, select
Credentials -> Add credentials -> OAuth2.0 client ID -> Web Application.
How is OAuth 2 different from OAuth 1?
OAuth 2 is apparently a waste of time (from the mouth of someone that was heavily involved in it):
https://hueniverse.com/oauth-2-0-and-the-road-to-hell-8eec45921529
He says (edited for brevity and bolded for emphasis):
...I can no longer be
associated with the OAuth 2.0 standard. I resigned my role as lead
author and editor, withdraw my name from the specification, and left
the working group. Removing my name from a document I have
painstakingly labored over for three years and over two dozen drafts
was not easy. Deciding to move on from an effort I have led for over
five years was agonizing.
...At the end, I reached the conclusion that OAuth 2.0 is a bad
protocol. WS-* bad. It is bad enough that I no longer want to be
associated with it. ...When compared with OAuth 1.0, the 2.0
specification is more complex, less interoperable, less useful, more
incomplete, and most importantly, less secure.
To be clear, OAuth 2.0 at the hand of a developer with deep
understanding of web security will likely result is a secure
implementation. However, at the hands of most developers – as has been
the experience from the past two years – 2.0 is likely to produce
insecure implementations.
Error :Request header field Content-Type is not allowed by Access-Control-Allow-Headers
For Nginx, the only thing that worked for me was adding this header:
add_header 'Access-Control-Allow-Headers' 'Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since';
Along with the Access-Control-Allow-Origin header:
add_header 'Access-Control-Allow-Origin' '*';
Then reloaded the nginx config and it worked great. Credit https://gist.github.com/algal/5480916.
Is there any JSON Web Token (JWT) example in C#?
It would be better to use standard and famous libraries instead of writing the code from scratch.
- JWT for encoding and decoding JWT tokens
- Bouncy Castle supports encryption and decryption, especially RS256 get it here
Using these libraries you can generate a JWT token and sign it using RS256 as below.
public string GenerateJWTToken(string rsaPrivateKey)
{
var rsaParams = GetRsaParameters(rsaPrivateKey);
var encoder = GetRS256JWTEncoder(rsaParams);
// create the payload according to the Google's doc
var payload = new Dictionary<string, object>
{
{ "iss", ""},
{ "sub", "" },
// and other key-values according to the doc
};
// add headers. 'alg' and 'typ' key-values are added automatically.
var header = new Dictionary<string, object>
{
{ "kid", "{your_private_key_id}" },
};
var token = encoder.Encode(header,payload, new byte[0]);
return token;
}
private static IJwtEncoder GetRS256JWTEncoder(RSAParameters rsaParams)
{
var csp = new RSACryptoServiceProvider();
csp.ImportParameters(rsaParams);
var algorithm = new RS256Algorithm(csp, csp);
var serializer = new JsonNetSerializer();
var urlEncoder = new JwtBase64UrlEncoder();
var encoder = new JwtEncoder(algorithm, serializer, urlEncoder);
return encoder;
}
private static RSAParameters GetRsaParameters(string rsaPrivateKey)
{
var byteArray = Encoding.ASCII.GetBytes(rsaPrivateKey);
using (var ms = new MemoryStream(byteArray))
{
using (var sr = new StreamReader(ms))
{
// use Bouncy Castle to convert the private key to RSA parameters
var pemReader = new PemReader(sr);
var keyPair = pemReader.ReadObject() as AsymmetricCipherKeyPair;
return DotNetUtilities.ToRSAParameters(keyPair.Private as RsaPrivateCrtKeyParameters);
}
}
}
ps: the RSA private key should have the following format:
-----BEGIN RSA PRIVATE KEY-----
{base64 formatted value}
-----END RSA PRIVATE KEY-----
How to call on a function found on another file?
Your sprite is created mid way through the playerSprite function... it also goes out of scope and ceases to exist at the end of that same function. The sprite must be created where you can pass it to playerSprite to initialize it and also where you can pass it to your draw function.
Perhaps declare it above your first while
?
Sending POST data in Android
Use the open source okHttp
library from Square. okHttp
works from Android 2.3 and up and has an Apache 2.0 license on GitHub.
Sending POST data is as simple as adding the following in an AsyncTask:
OkHttpClient client = new OkHttpClient();
RequestBody formBody = new FormBody.Builder()
.add("email", emailString) // A sample POST field
.add("comment", commentString) // Another sample POST field
.build();
Request request = new Request.Builder()
.url("https://yourdomain.org/callback.php") // The URL to send the data to
.post(formBody)
.build();
okHttp
also has a namespace on maven, so adding it to your Android Studio project is simple. Just add compile 'com.squareup.okhttp3:okhttp:3.11.0'
to your app's build.gradle.
Complete Code
Add the following to your activity:
public class CallAPI extends AsyncTask<String, String, String> {
String emailString;
String commentString;
public CallAPI(String email, String commnt){
emailString = email;
commentString = commnt;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(String... params) {
OkHttpClient client = new OkHttpClient();
RequestBody formBody = new FormBody.Builder()
.add("email", emailString) // A sample POST field
.add("comment", commentString) // Another sample POST field
.build();
Request request = new Request.Builder()
.url("https://yourdomain.org/callback.php") // The URL to send the data to
.post(formBody)
.build();
return "";
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
}
}
And call it using:
new CallAPI(emailString, commentString).execute();
Execute Python script via crontab
Put your script in a file foo.py
starting with
#!/usr/bin/python
Then give execute permission to that script using
chmod a+x foo.py
and use the full path of your foo.py
file in your crontab
.
See documentation of execve(2) which is handling the shebang.
Check list of words in another string
If your list of words is of substantial length, and you need to do this test many times, it may be worth converting the list to a set and using set intersection to test (with the added benefit that you wil get the actual words that are in both lists):
>>> long_word_list = 'some one long two phrase three about above along after against'
>>> long_word_set = set(long_word_list.split())
>>> set('word along river'.split()) & long_word_set
set(['along'])
How do I import a .bak file into Microsoft SQL Server 2012?
For SQL Server 2008, I would imagine the procedure is similar...?
- open SQL Server Management Studio
- log in to a SQL Server instance, right click on "Databases", select "Restore Database"
- wizard appears, you want "from device" which allows you to select a .bak file
Modifying location.hash without page scrolling
I was recently building a carousel which relies on window.location.hash
to maintain state and made the discovery that Chrome and webkit browsers will force scrolling (even to a non visible target) with an awkward jerk when the window.onhashchange
event is fired.
Even attempting to register a handler which stops propogation:
$(window).on("hashchange", function(e) {
e.stopPropogation();
e.preventDefault();
});
Did nothing to stop the default browser behavior.
The solution I found was using window.history.pushState
to change the hash without triggering the undesirable side-effects.
$("#buttons li a").click(function(){
var $self, id, oldUrl;
$self = $(this);
id = $self.attr('id');
$self.siblings().removeClass('selected'); // Don't re-query the DOM!
$self.addClass('selected');
if (window.history.pushState) {
oldUrl = window.location.toString();
// Update the address bar
window.history.pushState({}, '', '#' + id);
// Trigger a custom event which mimics hashchange
$(window).trigger('my.hashchange', [window.location.toString(), oldUrl]);
} else {
// Fallback for the poors browsers which do not have pushState
window.location.hash = id;
}
// prevents the default action of clicking on a link.
return false;
});
You can then listen for both the normal hashchange event and my.hashchange
:
$(window).on('hashchange my.hashchange', function(e, newUrl, oldUrl){
// @todo - do something awesome!
});
What is the difference between "mvn deploy" to a local repo and "mvn install"?
"matt b" has it right, but to be specific, the "install" goal copies your built target to the local repository on your file system; useful for small changes across projects not currently meant for the full group.
The "deploy" goal uploads it to your shared repository for when your work is finished, and then can be shared by other people who require it for their project.
In your case, it seems that "install" is used to make the management of the deployment easier since CI's local repo is the shared repo. If CI was on another box, it would have to use the "deploy" goal.
How do I create a basic UIButton programmatically?
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button addTarget:self
action:@selector(aMethod:)
forControlEvents:UIControlEventTouchDown];
[button setTitle:@"Show View" forState:UIControlStateNormal];
button.frame = CGRectMake(80.0, 210.0, 160.0, 40.0);
[view addSubview:button];
Verifying that a string contains only letters in C#
Recently, I made performance improvements for a function that checks letters in a string with the help of this page.
I figured out that the Solutions with regex are 30 times slower than the ones with the Char.IsLetterOrDigit check.
We were not sure that those Letters or Digits include and we were in need of only Latin characters so implemented our function based on the decompiled version of Char.IsLetterOrDigit function.
Here is our solution:
internal static bool CheckAllowedChars(char uc)
{
switch (uc)
{
case '-':
case '.':
case 'A':
case 'B':
case 'C':
case 'D':
case 'E':
case 'F':
case 'G':
case 'H':
case 'I':
case 'J':
case 'K':
case 'L':
case 'M':
case 'N':
case 'O':
case 'P':
case 'Q':
case 'R':
case 'S':
case 'T':
case 'U':
case 'V':
case 'W':
case 'X':
case 'Y':
case 'Z':
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
return true;
default:
return false;
}
}
And the usage is like this:
if( logicalId.All(c => CheckAllowedChars(c)))
{ // Do your stuff here.. }
Remove a file from the list that will be committed
You want to do this:
git add -u
git reset HEAD path/to/file
git commit
Be sure and do this from the top level of the repo; add -u
adds changes in the current directory (recursively).
The key line tells git to reset the version of the given path in the index (the staging area for the commit) to the version from HEAD (the currently checked-out commit).
And advance warning of a gotcha for others reading this: add -u
stages all modifications, but doesn't add untracked files. This is the same as what commit -a
does. If you want to add untracked files too, use add .
to recursively add everything.
How do I set a cookie on HttpClient's HttpRequestMessage
For me the simple solution works to set cookies in HttpRequestMessage object.
protected async Task<HttpResponseMessage> SendRequest(HttpRequestMessage requestMessage, CancellationToken cancellationToken = default(CancellationToken))
{
requestMessage.Headers.Add("Cookie", $"<Cookie Name 1>=<Cookie Value 1>;<Cookie Name 2>=<Cookie Value 2>");
return await _httpClient.SendAsync(requestMessage, cancellationToken).ConfigureAwait(false);
}
Auto increment in MongoDB to store sequence of Unique User ID
I know this is an old question, but I shall post my answer for posterity...
It depends on the system that you are building and the particular business rules in place.
I am building a moderate to large scale CRM in MongoDb, C# (Backend API), and Angular (Frontend web app) and found ObjectId utterly terrible for use in Angular Routing for selecting particular entities. Same with API Controller routing.
The suggestion above worked perfectly for my project.
db.contacts.insert({
"id":db.contacts.find().Count()+1,
"name":"John Doe",
"emails":[
"[email protected]",
"[email protected]"
],
"phone":"555111322",
"status":"Active"
});
The reason it is perfect for my case, but not all cases is that as the above comment states, if you delete 3 records from the collection, you will get collisions.
My business rules state that due to our in house SLA's, we are not allowed to delete correspondence data or clients records for longer than the potential lifespan of the application I'm writing, and therefor, I simply mark records with an enum "Status" which is either "Active" or "Deleted". You can delete something from the UI, and it will say "Contact has been deleted" but all the application has done is change the status of the contact to "Deleted" and when the app calls the respository for a list of contacts, I filter out deleted records before pushing the data to the client app.
Therefore, db.collection.find().count() + 1 is a perfect solution for me...
It won't work for everyone, but if you will not be deleting data, it works fine.
Jenkins pipeline if else not working
if ( params.build_deploy == '1' ) {
println "build_deploy ? ${params.build_deploy}"
jobB = build job: 'k8s-core-user_deploy', propagate: false, wait: true, parameters: [
string(name:'environment', value: "${params.environment}"),
string(name:'branch_name', value: "${params.branch_name}"),
string(name:'service_name', value: "${params.service_name}"),
]
println jobB.getResult()
}
How to return 2 values from a Java method?
Here is the really simple and short solution with SimpleEntry:
AbstractMap.Entry<String, Float> myTwoCents=new AbstractMap.SimpleEntry<>("maximum possible performance reached" , 99.9f);
String question=myTwoCents.getKey();
Float answer=myTwoCents.getValue();
Only uses Java built in functions and it comes with the type safty benefit.
Oracle: How to filter by date and time in a where clause
Put it this way
where ("R"."TIME_STAMP">=TO_DATE ('03-02-2013 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
AND "R"."TIME_STAMP"<=TO_DATE ('09-02-2013 23:59:59', 'DD-MM-YYYY HH24:MI:SS'))
Where
R is table name.
TIME_STAMP is FieldName in Table R.
Force index use in Oracle
There is an appropriate index on column_having_index, and its use actually increase performance, but Oracle didn't use it...
You should gather statistics on your table to let optimizer see that index access can help. Using direct hint is not a good practice.
Get data type of field in select statement in ORACLE
I found a not-very-intuitive way to do this by using DUMP()
SELECT DUMP(A.NAME),
DUMP(A.surname),
DUMP(B.ordernum)
FROM customer A
JOIN orders B
ON A.id = B.id
It will return something like:
'Typ=1 Len=2: 0,48'
for each column.
Type=1
means VARCHAR2/NVARCHAR2
Type=2
means NUMBER/FLOAT
Type=12
means DATE
, etc.
You can refer to this oracle doc for information Datatype Code
or this for a simple mapping Oracle Type Code Mappings
Are there any style options for the HTML5 Date picker?
found this on Zurb's github
In case you want to do some more custom styling. Here's all the
default CSS for webkit rendering of the date components.
input[type="date"] {
-webkit-align-items: center;
display: -webkit-inline-flex;
font-family: monospace;
overflow: hidden;
padding: 0;
-webkit-padding-start: 1px;
}
input::-webkit-datetime-edit {
-webkit-flex: 1;
-webkit-user-modify: read-only !important;
display: inline-block;
min-width: 0;
overflow: hidden;
}
input::-webkit-datetime-edit-fields-wrapper {
-webkit-user-modify: read-only !important;
display: inline-block;
padding: 1px 0;
white-space: pre;
}
How to make a programme continue to run after log out from ssh?
Assuming that you have a program running in the foreground, press ctrl-Z, then:
[1]+ Stopped myprogram
$ disown -h %1
$ bg 1
[1]+ myprogram &
$ logout
If there is only one job, then you don't need to specify the job number. Just use disown -h
and bg
.
Explanation of the above steps:
You press ctrl-Z. The system suspends the running program, displays a job number and a "Stopped" message and returns you to a bash prompt.
You type the disown -h %1
command (here, I've used a 1
, but you'd use the job number that was displayed in the Stopped
message) which marks the job so it ignores the SIGHUP
signal (it will not be stopped by logging out).
Next, type the bg
command using the same job number; this resumes the running of the program in the background and a message is displayed confirming that.
You can now log out and it will continue running..
tkinter: how to use after method
I believe, the 500ms run in the background, while the rest of the code continues to execute and empties the list.
Then after 500ms nothing happens, as no function-call is implemented in the after-callup (same as frame.after(500, function=None)
)
Sequence contains more than one element
FYI you can also get this error if EF Migrations tries to run with no Db configured, for example in a Test Project.
Chased this for hours before I figured out that it was erroring on a query, but, not because of the query but because it was when Migrations kicked in to try to create the Db.
Dynamically updating css in Angular 2
Try this
<div class="home-component"
[style.width.px]="width"
[style.height.px]="height">Some stuff in this div</div>
[Updated]:
To set in % use
[style.height.%]="height">Some stuff in this div</div>
C# guid and SQL uniqueidentifier
Here's a code snippet showing how to insert a GUID using a parameterised query:
using(SqlConnection conn = new SqlConnection(connectionString))
{
conn.Open();
using(SqlTransaction trans = conn.BeginTransaction())
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.Transaction = trans;
cmd.CommandText = @"INSERT INTO [MYTABLE] ([GuidValue]) VALUE @guidValue;";
cmd.Parameters.AddWithValue("@guidValue", Guid.NewGuid());
cmd.ExecuteNonQuery();
trans.Commit();
}
}
How can I wait In Node.js (JavaScript)? l need to pause for a period of time
simple we are going to wait for 5 seconds for some event to happen (that would be indicated by done variable set to true somewhere else in the code) or when timeout expires that we will check every 100ms
var timeout=5000; //will wait for 5 seconds or untildone
var scope = this; //bind this to scope variable
(function() {
if (timeout<=0 || scope.done) //timeout expired or done
{
scope.callback();//some function to call after we are done
}
else
{
setTimeout(arguments.callee,100) //call itself again until done
timeout -= 100;
}
})();
Use RSA private key to generate public key?
here in this code first we are creating RSA key which is private but it has pair of its public key as well so to get your actual public key we simply do this
openssl rsa -in mykey.pem -pubout > mykey.pub
hope you get it for more info check this
HTML encoding issues - "Â" character showing up instead of " "
Somewhere in that mess, the non-breaking spaces from the HTML template (the s) are encoding as ISO-8859-1 so that they show up incorrectly as an "Â" character
That'd be encoding to UTF-8 then, not ISO-8859-1. The non-breaking space character is byte 0xA0 in ISO-8859-1; when encoded to UTF-8 it'd be 0xC2,0xA0, which, if you (incorrectly) view it as ISO-8859-1 comes out as "Â "
. That includes a trailing nbsp which you might not be noticing; if that byte isn't there, then something else has mauled your document and we need to see further up to find out what.
What's the regexp, how does the templating work? There would seem to be a proper HTML parser involved somewhere if your
strings are (correctly) being turned into U+00A0 NON-BREAKING SPACE characters. If so, you could just process your template natively in the DOM, and ask it to serialise using the ASCII encoding to keep non-ASCII characters as character references. That would also stop you having to do regex post-processing on the HTML itself, which is always a highly dodgy business.
Well anyway, for now you can add one of the following to your document's <head>
and see if that makes it look right in the browser:
- for HTML4:
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
- for HTML5:
<meta charset="utf-8">
If you've done that, then any remaining problem is ActivePDF's fault.
Eclipse error: R cannot be resolved to a variable
I'm not posting this as an answer but a confirmation to Paresh's accepted answer. I recently updated SDK tools to Revision 22 and I noticed my code changes was not being affective on the device i'm testing at all. Such as the url I was using, I was getting errors for connection time out regarding the url I was "previously" using. Therefore I cleaned the project and built again only to find out that autogenerated R.java file is missing.
After reading Paresh's answer and checking what's going on with my sdk manager this is what I saw:
SDK Build-tools 17 was not installed and there was already a new update to SDK tools even though it does not mention any change related to this problem in the changelog, this update brought back my R.java file and the related problems were gone after an eclipse restart and final clean/rebuild on the project.
How can I loop through enum values for display in radio buttons?
Two options:
for (let item in MotifIntervention) {
if (isNaN(Number(item))) {
console.log(item);
}
}
Or
Object.keys(MotifIntervention).filter(key => !isNaN(Number(MotifIntervention[key])));
(code in playground)
Edit
String enums look different than regular ones, for example:
enum MyEnum {
A = "a",
B = "b",
C = "c"
}
Compiles into:
var MyEnum;
(function (MyEnum) {
MyEnum["A"] = "a";
MyEnum["B"] = "b";
MyEnum["C"] = "c";
})(MyEnum || (MyEnum = {}));
Which just gives you this object:
{
A: "a",
B: "b",
C: "c"
}
You can get all the keys (["A", "B", "C"]
) like this:
Object.keys(MyEnum);
And the values (["a", "b", "c"]
):
Object.keys(MyEnum).map(key => MyEnum[key])
Or using Object.values():
Object.values(MyEnum)
Shorthand if/else statement Javascript
Another way to write it shortly
bePlanVar = !!((bePlanVar == false));
// is equivalent to
bePlanVar = (bePlanVar == false) ? true : false;
// and
if (bePlanVar == false) {
bePlanVar = true;
} else {
bePlanVar = false;
}
How do I check if file exists in Makefile so I can delete it?
Missing a semicolon
if [ -a myApp ];
then
rm myApp
fi
However, I assume you are checking for existence before deletion to prevent an error message. If so, you can just use rm -f myApp
which "forces" delete, i.e. doesn't error out if the file didn't exist.
Run jQuery function onclick
Why do you need to attach it to the HTML? Just bind the function with hover
$("div.system_box").hover(function(){ mousin },
function() { mouseout });
If you do insist to have JS references inside the html, which is usualy a bad idea you can use:
onmouseover="yourJavaScriptCode()"
after topic edit:
<div class="system_box" data-target="sms_box">
...
$("div.system_box").click(function(){ slideonlyone($(this).attr("data-target")); });
Property 'value' does not exist on type EventTarget in TypeScript
add any type to event
event: any
example
[element].addEvenListener('mousemove', (event: any) =>{
//CODE//
} )
what happens is that typescript adds event as Event type and for some reason it doesn't recognize some properties. Adding it of type any no longer exists this problem, this works for any document.[Property]
How to convert hex to ASCII characters in the Linux shell?
You can use this command (python script) for larger inputs:
echo 58595a | python -c "import sys; import binascii; print(binascii.unhexlify(sys.stdin.read().strip()).decode())"
The result will be:
XYZ
And for more simplicity, define an alias:
alias hexdecoder='python -c "import sys; import binascii; print(binascii.unhexlify(sys.stdin.read().strip()).decode())"'
echo 58595a | hexdecoder
What is a void pointer in C++?
A void*
does not mean anything. It is a pointer, but the type that it points to is not known.
It's not that it can return "anything". A function that returns a void*
generally is doing one of the following:
- It is dealing in unformatted memory. This is what
operator new
and malloc
return: a pointer to a block of memory of a certain size. Since the memory does not have a type (because it does not have a properly constructed object in it yet), it is typeless. IE: void
.
- It is an opaque handle; it references a created object without naming a specific type. Code that does this is generally poorly formed, since this is better done by forward declaring a struct/class and simply not providing a public definition for it. Because then, at least it has a real type.
- It returns a pointer to storage that contains an object of a known type. However, that API is used to deal with objects of a wide variety of types, so the exact type that a particular call returns cannot be known at compile time. Therefore, there will be some documentation explaining when it stores which kinds of objects, and therefore which type you can safely cast it to.
This construct is nothing like dynamic
or object
in C#. Those tools actually know what the original type is; void*
does not. This makes it far more dangerous than any of those, because it is very easy to get it wrong, and there's no way to ask if a particular usage is the right one.
And on a personal note, if you see code that uses void*
's "often", you should rethink what code you're looking at. void*
usage, especially in C++, should be rare, used primary for dealing in raw memory.
How do I convert between big-endian and little-endian values in C++?
Note that, at least for Windows, htonl() is much slower than their intrinsic counterpart _byteswap_ulong(). The former is a DLL library call into ws2_32.dll, the latter is one BSWAP assembly instruction. Therefore, if you are writing some platform-dependent code, prefer using the intrinsics for speed:
#define htonl(x) _byteswap_ulong(x)
This may be especially important for .PNG image processing where all integers are saved in Big Endian with explanation "One can use htonl()..." {to slow down typical Windows programs, if you are not prepared}.
Flutter - Layout a Grid
Please visit this repo.
Widget _gridView() {
return GridView.count(
crossAxisCount: 4,
padding: EdgeInsets.all(4.0),
childAspectRatio: 8.0 / 9.0,
children: itemList
.map(
(Item) => ItemList(item: Item),
)
.toList(),
);
}
Below screenshot contains crossAxisCount: 2
What do the terms "CPU bound" and "I/O bound" mean?
An application is CPU-bound when the arithmetic/logical/floating-point (A/L/FP) performance during the execution is mostly near the theoretical peak-performance of the processor (data provided by the manufacturer and determined by the characteristics of the processor: number of cores, frequency, registers, ALUs, FPUs, etc.).
The peek performance is very difficult to be achieved in real-world applications, for not saying impossible. Most of the applications access memory in different parts of the execution and the processor is not doing A/L/FP operations during several cycles. This is called Von Neumann Limitation due to the distance that exists between the memory and the processor.
If you want to be near the CPU peak-performance a strategy could be to try to reuse most of the data in the cache memory in order to avoid requiring data from the main memory. An algorithm that exploits this feature is the matrix-matrix multiplication (if both matrices can be stored in the cache memory). This happens because if the matrices are size n x n
then you need to do about 2 n^3
operations using only 2 n^2
FP numbers of data. On the other hand matrix addition, for example, is a less CPU-bound or a more memory-bound application than the matrix multiplication since it requires only n^2
FLOPs with the same data.
In the following figure the FLOPs obtained with a naive algorithms for the matrix addition and the matrix multiplication in an Intel i5-9300H, is shown:
Note that as expected the performance of the matrix multiplication in bigger than the matrix addition. These results can be reproduced by running test/gemm
and test/matadd
available in this repository.
I suggest also to see the video given by J. Dongarra about this effect.
OpenCV & Python - Image too big to display
The other answers perform a fixed (width, height)
resize. If you wanted to resize to a specific size while maintaining aspect ratio, use this
def ResizeWithAspectRatio(image, width=None, height=None, inter=cv2.INTER_AREA):
dim = None
(h, w) = image.shape[:2]
if width is None and height is None:
return image
if width is None:
r = height / float(h)
dim = (int(w * r), height)
else:
r = width / float(w)
dim = (width, int(h * r))
return cv2.resize(image, dim, interpolation=inter)
Example
image = cv2.imread('img.png')
resize = ResizeWithAspectRatio(image, width=1280) # Resize by width OR
# resize = ResizeWithAspectRatio(image, height=1280) # Resize by height
cv2.imshow('resize', resize)
cv2.waitKey()
Get current domain
Everybody is using the parse_url
function, but sometimes user may pass the argumet in different format.
So as to fix that, I have created the function. Check this out:
function fixDomainName($url='')
{
$strToLower = strtolower(trim($url));
$httpPregReplace = preg_replace('/^http:\/\//i', '', $strToLower);
$httpsPregReplace = preg_replace('/^https:\/\//i', '', $httpPregReplace);
$wwwPregReplace = preg_replace('/^www\./i', '', $httpsPregReplace);
$explodeToArray = explode('/', $wwwPregReplace);
$finalDomainName = trim($explodeToArray[0]);
return $finalDomainName;
}
Just pass the URL and get the domain.
For example,
echo fixDomainName('https://stackoverflow.com');
will return the result will be
stackoverflow.com
And in some situation:
echo fixDomainName('stackoverflow.com/questions/id/slug');
And it will also return stackoverflow.com
.
Mysql service is missing
Go to your mysql bin directory and install mysql service again:
c:
cd \mysql\bin
mysqld-nt.exe --install
or if mysqld-nt.exe is missing (depending on version):
mysqld.exe --install
Then go to services, start the service and set it to automatic start.
What does elementFormDefault do in XSD?
I have noticed that XMLSpy(at least 2011 version)needs a targetNameSpace defined if elementFormDefault="qualified" is used. Otherwise won't validate. And also won't generate xmls with namespace prefixes
Can I access constants in settings.py from templates in Django?
If using a class-based view:
#
# in settings.py
#
YOUR_CUSTOM_SETTING = 'some value'
#
# in views.py
#
from django.conf import settings #for getting settings vars
class YourView(DetailView): #assuming DetailView; whatever though
# ...
def get_context_data(self, **kwargs):
context = super(YourView, self).get_context_data(**kwargs)
context['YOUR_CUSTOM_SETTING'] = settings.YOUR_CUSTOM_SETTING
return context
#
# in your_template.html, reference the setting like any other context variable
#
{{ YOUR_CUSTOM_SETTING }}
Java String encoding (UTF-8)
This could be complicated way of doing
String newString = new String(oldString);
This shortens the String is the underlying char[] used is much longer.
However more specifically it will be checking that every character can be UTF-8 encoded.
There are some "characters" you can have in a String which cannot be encoded and these would be turned into ?
Any character between \uD800 and \uDFFF cannot be encoded and will be turned into '?'
String oldString = "\uD800";
String newString = new String(oldString.getBytes("UTF-8"), "UTF-8");
System.out.println(newString.equals(oldString));
prints
false
Build a basic Python iterator
This is an iterable function without yield
. It make use of the iter
function and a closure which keeps it's state in a mutable (list
) in the enclosing scope for python 2.
def count(low, high):
counter = [0]
def tmp():
val = low + counter[0]
if val < high:
counter[0] += 1
return val
return None
return iter(tmp, None)
For Python 3, closure state is kept in an immutable in the enclosing scope and nonlocal
is used in local scope to update the state variable.
def count(low, high):
counter = 0
def tmp():
nonlocal counter
val = low + counter
if val < high:
counter += 1
return val
return None
return iter(tmp, None)
Test;
for i in count(1,10):
print(i)
1
2
3
4
5
6
7
8
9
Extract a substring using PowerShell
Since the string is not complex, no need to add RegEx strings. A simple match will do the trick
$line = "----start----Hello World----end----"
$line -match "Hello World"
$matches[0]
Hello World
$result = $matches[0]
$result
Hello World
CSV new-line character seen in unquoted field error
It'll be good to see the csv file itself, but this might work for you, give it a try, replace:
file_read = csv.reader(self.file)
with:
file_read = csv.reader(self.file, dialect=csv.excel_tab)
Or, open a file with universal newline mode
and pass it to csv.reader
, like:
reader = csv.reader(open(self.file, 'rU'), dialect=csv.excel_tab)
Or, use splitlines()
, like this:
def read_file(self):
with open(self.file, 'r') as f:
data = [row for row in csv.reader(f.read().splitlines())]
return data
How do I get the APK of an installed app without root access?
On Nougat(7.0) Android version run adb shell pm list packages
to list the packages installed on the device.
Then run adb shell pm path your-package-name
to show the path of the apk.
After use adb to copy the package to Downloads adb shell cp /data/app/com.test-1/base.apk /storage/emulated/0/Download
.
Then pull the apk from Downloads to your machine by running adb pull /storage/emulated/0/Download/base.apk
.
What is a typedef enum in Objective-C?
enum can reduce many types of "errors" and make the code more manageable
#define STATE_GOOD 0
#define STATE_BAD 1
#define STATE_OTHER 2
int STATE = STATE_OTHER
The definition has no constraints. It's simply just a substitution.
It is not able to limit all conditions of the state. When the STATE is assigned to 5, the program will be wrong, because there is no matching state. But the compiler is not going to warn STATE = 5
So it is better to use like this
typedef enum SampleState {
SampleStateGood = 0,
SampleStateBad,
SampleStateOther
} SampleState;
SampleState state = SampleStateGood;
Convert datetime to Unix timestamp and convert it back in python
What you missed here is timezones.
Presumably you've five hours off UTC, so 2013-09-01T11:00:00 local and 2013-09-01T06:00:00Z are the same time.
You need to read the top of the datetime
docs, which explain about timezones and "naive" and "aware" objects.
If your original naive datetime was UTC, the way to recover it is to use utcfromtimestamp
instead of fromtimestamp
.
On the other hand, if your original naive datetime was local, you shouldn't have subtracted a UTC timestamp from it in the first place; use datetime.fromtimestamp(0)
instead.
Or, if you had an aware datetime object, you need to either use a local (aware) epoch on both sides, or explicitly convert to and from UTC.
If you have, or can upgrade to, Python 3.3 or later, you can avoid all of these problems by just using the timestamp
method instead of trying to figure out how to do it yourself. And even if you don't, you may want to consider borrowing its source code.
(And if you can wait for Python 3.4, it looks like PEP 341 is likely to make it into the final release, which means all of the stuff J.F. Sebastian and I were talking about in the comments should be doable with just the stdlib, and working the same way on both Unix and Windows.)
Reliable and fast FFT in Java
I wrote a function for the FFT in Java: http://www.wikijava.org/wiki/The_Fast_Fourier_Transform_in_Java_%28part_1%29
It's in the Public Domain so you can use those functions everywhere (personal or business projects too). Just cite me in the credits and send me just a link of your work, and you're ok.
It is completely reliable. I've checked its output against the Mathematica's FFT and they were always correct until the 15th decimal digit. I think it's a very good FFT implementation for Java. I wrote it on the J2SE 1.6 version, and tested it on the J2SE 1.5-1.6 version.
If you count the number of instruction (it's a lot much simpler than a perfect computational complexity function estimation) you can clearly see that this version is great even if it's not optimized at all. I'm planning to publish the optimized version if there are enough requests.
Let me know if it was useful, and tell me any comment you like.
I share the same code right here:
/**
* @author Orlando Selenu
*
*/
public class FFTbase {
/**
* The Fast Fourier Transform (generic version, with NO optimizations).
*
* @param inputReal
* an array of length n, the real part
* @param inputImag
* an array of length n, the imaginary part
* @param DIRECT
* TRUE = direct transform, FALSE = inverse transform
* @return a new array of length 2n
*/
public static double[] fft(final double[] inputReal, double[] inputImag,
boolean DIRECT) {
// - n is the dimension of the problem
// - nu is its logarithm in base e
int n = inputReal.length;
// If n is a power of 2, then ld is an integer (_without_ decimals)
double ld = Math.log(n) / Math.log(2.0);
// Here I check if n is a power of 2. If exist decimals in ld, I quit
// from the function returning null.
if (((int) ld) - ld != 0) {
System.out.println("The number of elements is not a power of 2.");
return null;
}
// Declaration and initialization of the variables
// ld should be an integer, actually, so I don't lose any information in
// the cast
int nu = (int) ld;
int n2 = n / 2;
int nu1 = nu - 1;
double[] xReal = new double[n];
double[] xImag = new double[n];
double tReal, tImag, p, arg, c, s;
// Here I check if I'm going to do the direct transform or the inverse
// transform.
double constant;
if (DIRECT)
constant = -2 * Math.PI;
else
constant = 2 * Math.PI;
// I don't want to overwrite the input arrays, so here I copy them. This
// choice adds \Theta(2n) to the complexity.
for (int i = 0; i < n; i++) {
xReal[i] = inputReal[i];
xImag[i] = inputImag[i];
}
// First phase - calculation
int k = 0;
for (int l = 1; l <= nu; l++) {
while (k < n) {
for (int i = 1; i <= n2; i++) {
p = bitreverseReference(k >> nu1, nu);
// direct FFT or inverse FFT
arg = constant * p / n;
c = Math.cos(arg);
s = Math.sin(arg);
tReal = xReal[k + n2] * c + xImag[k + n2] * s;
tImag = xImag[k + n2] * c - xReal[k + n2] * s;
xReal[k + n2] = xReal[k] - tReal;
xImag[k + n2] = xImag[k] - tImag;
xReal[k] += tReal;
xImag[k] += tImag;
k++;
}
k += n2;
}
k = 0;
nu1--;
n2 /= 2;
}
// Second phase - recombination
k = 0;
int r;
while (k < n) {
r = bitreverseReference(k, nu);
if (r > k) {
tReal = xReal[k];
tImag = xImag[k];
xReal[k] = xReal[r];
xImag[k] = xImag[r];
xReal[r] = tReal;
xImag[r] = tImag;
}
k++;
}
// Here I have to mix xReal and xImag to have an array (yes, it should
// be possible to do this stuff in the earlier parts of the code, but
// it's here to readibility).
double[] newArray = new double[xReal.length * 2];
double radice = 1 / Math.sqrt(n);
for (int i = 0; i < newArray.length; i += 2) {
int i2 = i / 2;
// I used Stephen Wolfram's Mathematica as a reference so I'm going
// to normalize the output while I'm copying the elements.
newArray[i] = xReal[i2] * radice;
newArray[i + 1] = xImag[i2] * radice;
}
return newArray;
}
/**
* The reference bitreverse function.
*/
private static int bitreverseReference(int j, int nu) {
int j2;
int j1 = j;
int k = 0;
for (int i = 1; i <= nu; i++) {
j2 = j1 / 2;
k = 2 * k + j1 - 2 * j2;
j1 = j2;
}
return k;
}
}
How to kill a thread instantly in C#?
You can kill instantly doing it in that way:
private Thread _myThread = new Thread(SomeThreadMethod);
private void SomeThreadMethod()
{
// do whatever you want
}
[SecurityPermissionAttribute(SecurityAction.Demand, ControlThread = true)]
private void KillTheThread()
{
_myThread.Abort();
}
I always use it and works for me:)
setTimeout or setInterval?
They essentially try to do the same thing, but the setInterval
approach will be more accurate than the setTimeout
approach, since setTimeout
waits 1000ms, runs the function and then sets another timeout. So the wait period is actually a bit more than 1000ms (or a lot more if your function takes a long time to execute).
Although one might think that setInterval
will execute exactly every 1000ms, it is important to note that setInterval
will also delay, since JavaScript isn't a multi-threaded language, which means that - if there are other parts of the script running - the interval will have to wait for that to finish.
In this Fiddle, you can clearly see that the timeout will fall behind, while the interval is almost all the time at almost 1 call/second (which the script is trying to do). If you change the speed variable at the top to something small like 20 (meaning it will try to run 50 times per second), the interval will never quite reach an average of 50 iterations per second.
The delay is almost always negligible, but if you're programming something really precise, you should go for a self-adjusting timer (which essentially is a timeout-based timer that constantly adjusts itself for the delay it's created)
Where IN clause in LINQ
from state in _objedatasource.StateList()
where listofcountrycodes.Contains(state.CountryCode)
select state
Why is document.body null in my javascript?
Or add this part
<script type="text/javascript">
var mySpan = document.createElement("span");
mySpan.innerHTML = "This is my span!";
mySpan.style.color = "red";
document.body.appendChild(mySpan);
alert("Why does the span change after this alert? Not before?");
</script>
after the HTML, like:
<html>
<head>...</head>
<body>...</body>
<script type="text/javascript">
var mySpan = document.createElement("span");
mySpan.innerHTML = "This is my span!";
mySpan.style.color = "red";
document.body.appendChild(mySpan);
alert("Why does the span change after this alert? Not before?");
</script>
</html>
Create nice column output in python
I found this answer super-helpful and elegant, originally from here:
matrix = [["A", "B"], ["C", "D"]]
print('\n'.join(['\t'.join([str(cell) for cell in row]) for row in matrix]))
Output
A B
C D
Does the Java &= operator apply & or &&?
Here's a simple way to test it:
public class OperatorTest {
public static void main(String[] args) {
boolean a = false;
a &= b();
}
private static boolean b() {
System.out.println("b() was called");
return true;
}
}
The output is b() was called
, therefore the right-hand operand is evaluated.
So, as already mentioned by others, a &= b
is the same as a = a & b
.
How to create a drop-down list?
Try this...
<string-array name="names">
<item></item>
<item>By Bus</item>
<item>By Train</item>
<item>By Van</item>
<item>By Bike</item>
</string-array>
String travel_type;
ArrayAdapter<String> myAdapter = new ArrayAdapter(AddNew_Trip.this,android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.names));
myAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
mySpinner.setAdapter(myAdapter);
mySpinner.setOnItemSelectedListener(
new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
travel_type = String.valueOf(adapterView.getItemAtPosition(i));
//Toast.makeText(Plan_Trip.this, travel_type, Toast.LENGTH_SHORT).show();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
}
);
}
How To Get Selected Value From UIPickerView
You will need to ask the picker's delegate, in the same way your application does. Here is how I do it from within my UIPickerViewDelegate:
func selectedRowValue(picker : UIPickerView, ic : Int) -> String {
//Row Index
let ir = picker.selectedRow(inComponent: ic);
//Value
let val = self.pickerView(picker,
titleForRow: ir,
forComponent: ic);
return val!;
}
"make clean" results in "No rule to make target `clean'"
You have fallen victim to the most common of errors in Makefiles. You always need to put a Tab at the beginning of each command. You've put spaces before the $(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
and @rm -f $(PROGRAMS) *.o core
lines. If you replace them with a Tab, you'll be fine.
However, this error doesn't lead to a "No rule to make target ..." error. That probably means your issue lies beyond your Makefile. Have you checked this is the correct Makefile, as in the one you want to be specifying your commands? Try explicitly passing it as a parameter to make, make -f Makefile
and let us know what happens.
add title attribute from css
As Quentin and other suggested this cannot totally be done with css(partially done with content attribute of css). Instead you should use javascript/jQuery to achieve this,
JS:
document.getElementsByClassName("mandatory")[0].title = "mandatory";
or using jQuery:
$('.mandatory').attr('title','mandatory');
_x000D_
_x000D_
document.getElementsByClassName('mandatory')[0].setAttribute('title', 'mandatory');_x000D_
_x000D_
$('.jmandatory').attr('title', 'jmandatory');
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
Place the Mouse Over the following elements to see the title,_x000D_
<br/><br/>_x000D_
<b><label class="mandatory">->Javascript Mandatory</label></b>_x000D_
<br/><br/>_x000D_
<b><label class="jmandatory">->jQuery Mandatory</label></b>
_x000D_
_x000D_
_x000D_
How to save public key from a certificate in .pem format
There are a couple ways to do this.
First, instead of going into openssl command prompt mode, just enter everything on one command line from the Windows prompt:
E:\> openssl x509 -pubkey -noout -in cert.pem > pubkey.pem
If for some reason, you have to use the openssl command prompt, just enter everything up to the ">". Then OpenSSL will print out the public key info to the screen. You can then copy this and paste it into a file called pubkey.pem.
openssl> x509 -pubkey -noout -in cert.pem
Output will look something like this:
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAryQICCl6NZ5gDKrnSztO
3Hy8PEUcuyvg/ikC+VcIo2SFFSf18a3IMYldIugqqqZCs4/4uVW3sbdLs/6PfgdX
7O9D22ZiFWHPYA2k2N744MNiCD1UE+tJyllUhSblK48bn+v1oZHCM0nYQ2NqUkvS
j+hwUU3RiWl7x3D2s9wSdNt7XUtW05a/FXehsPSiJfKvHJJnGOX0BgTvkLnkAOTd
OrUZ/wK69Dzu4IvrN4vs9Nes8vbwPa/ddZEzGR0cQMt0JBkhk9kU/qwqUseP1QRJ
5I1jR4g8aYPL/ke9K35PxZWuDp3U0UPAZ3PjFAh+5T+fc7gzCs9dPzSHloruU+gl
FQIDAQAB
-----END PUBLIC KEY-----
Difference in days between two dates in Java?
You should use Joda Time library because Java Util Date returns wrong values sometimes.
Joda vs Java Util Date
For example days between yesterday (dd-mm-yyyy, 12-07-2016) and first day of year in 1957 (dd-mm-yyyy, 01-01-1957):
public class Main {
public static void main(String[] args) {
SimpleDateFormat format = new SimpleDateFormat("dd-MM-yyyy");
Date date = null;
try {
date = format.parse("12-07-2016");
} catch (ParseException e) {
e.printStackTrace();
}
//Try with Joda - prints 21742
System.out.println("This is correct: " + getDaysBetweenDatesWithJodaFromYear1957(date));
//Try with Java util - prints 21741
System.out.println("This is not correct: " + getDaysBetweenDatesWithJavaUtilFromYear1957(date));
}
private static int getDaysBetweenDatesWithJodaFromYear1957(Date date) {
DateTime jodaDateTime = new DateTime(date);
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd-MM-yyyy");
DateTime y1957 = formatter.parseDateTime("01-01-1957");
return Days.daysBetween(y1957 , jodaDateTime).getDays();
}
private static long getDaysBetweenDatesWithJavaUtilFromYear1957(Date date) {
SimpleDateFormat format = new SimpleDateFormat("dd-MM-yyyy");
Date y1957 = null;
try {
y1957 = format.parse("01-01-1957");
} catch (ParseException e) {
e.printStackTrace();
}
return TimeUnit.DAYS.convert(date.getTime() - y1957.getTime(), TimeUnit.MILLISECONDS);
}
So I really advice you to use Joda Time library.
release Selenium chromedriver.exe from memory
Observed on version 3.141.0:
If you initialize your ChromeDriver with just ChromeOptions, quit() will not close out chromedriver.exe.
ChromeOptions chromeOptions = new ChromeOptions();
ChromeDriver driver = new ChromeDriver(chromeOptions);
// .. do stuff ..
driver.quit()
If you create and pass in a ChromeDriverService, quit() will close chromedriver.exe out correctly.
ChromeDriverService driverService = ChromeDriverService.CreateDefaultService();
ChromeOptions chromeOptions = new ChromeOptions();
ChromeDriver driver = new ChromeDriver(driverService, chromeOptions);
// .. do stuff ..
driver.quit()
How to Apply Mask to Image in OpenCV?
You don't apply a binary mask to an image. You (optionally) use a binary mask in a processing function call to tell the function which pixels of the image you want to process. If I'm completely misinterpreting your question, you should add more detail to clarify.
HTML Input Box - Disable
<input type="text" required="true" value="" readonly="true">
This will make a text box in readonly mode, might be helpful in generating passwords and datepickers.
log4j: Log output of a specific class to a specific appender
An example:
log4j.rootLogger=ERROR, logfile
log4j.appender.logfile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logfile.datePattern='-'dd'.log'
log4j.appender.logfile.File=log/radius-prod.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%-6r %d{ISO8601} %-5p %40.40c %x - %m\n
log4j.logger.foo.bar.Baz=DEBUG, myappender
log4j.additivity.foo.bar.Baz=false
log4j.appender.myappender=org.apache.log4j.DailyRollingFileAppender
log4j.appender.myappender.datePattern='-'dd'.log'
log4j.appender.myappender.File=log/access-ext-dmz-prod.log
log4j.appender.myappender.layout=org.apache.log4j.PatternLayout
log4j.appender.myappender.layout.ConversionPattern=%-6r %d{ISO8601} %-5p %40.40c %x - %m\n
How do I hide an element when printing a web page?
In your stylesheet add:
@media print
{
.no-print, .no-print *
{
display: none !important;
}
}
Then add class='no-print'
(or add the no-print class to an existing class statement) in your HTML that you don't want to appear in the printed version, such as your button.
Javascript Thousand Separator / string format
number = 123456.7089;
result = parseInt( number ).toLocaleString() + "<br>";
result = number.toLocaleString( 'pt-BR' ) + "<br>";
var el = document.getElementById( 'result' );
el.innerHTML = result;
<div id="result"></div>
How to allow user to pick the image with Swift?
If you just want let the user choose image with UIImagePickerController use this code:
import UIKit
class ViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
@IBOutlet var imageView: UIImageView!
@IBOutlet var chooseBuuton: UIButton!
var imagePicker = UIImagePickerController()
@IBAction func btnClicked() {
if UIImagePickerController.isSourceTypeAvailable(.savedPhotosAlbum){
print("Button capture")
imagePicker.delegate = self
imagePicker.sourceType = .savedPhotosAlbum
imagePicker.allowsEditing = false
present(imagePicker, animated: true, completion: nil)
}
}
func imagePickerController(picker: UIImagePickerController!, didFinishPickingImage image: UIImage!, editingInfo: NSDictionary!){
self.dismiss(animated: true, completion: { () -> Void in
})
imageView.image = image
}
}
How do I schedule jobs in Jenkins?
Jenkins uses Cron format on scheduling.
You can refer this link for more detailhttps://en.wikipedia.org/wiki/Cron.
One more thing, Jenkins provide us a very useful preview. Please take a look on the screenshot.
I hope this help. Thanks
500 Internal Server Error for php file not for html
500 Internal Server Error is shown if your php code has fatal errors but error displaying is switched off. You may try this to see the error itself instead of 500 error page:
In your php file:
ini_set('display_errors', 1);
In .htaccess file:
php_flag display_errors 1
PHP: how can I get file creation date?
Unfortunately if you are running on linux you cannot access the information as only the last modified date is stored.
It does slightly depend on your filesystem tho. I know that ext2 and ext3 do not support creation time but I think that ext4 does.
How to Parse a JSON Object In Android
In the end I solved it by using JSONObject.get
rather than JSONObject.getString
and then cast test
to a String
.
private void saveData(String result) {
try {
JSONObject json= (JSONObject) new JSONTokener(result).nextValue();
JSONObject json2 = json.getJSONObject("results");
test = (String) json2.get("name");
} catch (JSONException e) {
e.printStackTrace();
}
}
Run script on mac prompt "Permission denied"
Please read the whole answer before attempting to run with sudo
Try running sudo /dvtcolorconvert.rb ~/Themes/ObsidianCode.xccolortheme
The sudo command executes the commands which follow it with 'superuser' or 'root' privileges. This should allow you to execute almost anything from the command line. That said, DON'T DO THIS! If you are running a script on your computer and don't need it to access core components of your operating system (I'm guessing you're not since you are invoking the script on something inside your home directory (~/)), then it should be running from your home directory, ie:
~/dvtcolorconvert.rb ~/Themes/ObsidianCode.xccolortheme
Move it to ~/ or a sub directory and execute from there. You should never have permission issues there and there wont be a risk of it accessing or modifying anything critical to your OS.
If you are still having problems you can check the permissions on the file by running ls -l
while in the same directory as the ruby script. You will get something like this:
$ ls -l
total 13
drwxr-xr-x 4 or019268 Administ 12288 Apr 10 18:14 TestWizard
drwxr-xr-x 4 or019268 Administ 4096 Aug 27 12:41 Wizard.Controls
drwxr-xr-x 5 or019268 Administ 8192 Sep 5 00:03 Wizard.UI
-rw-r--r-- 1 or019268 Administ 1375 Sep 5 00:03 readme.txt
You will notice that the readme.txt file says -rw-r--r--
on the left. This shows the permissions for that file. The 9 characters from the right can be split into groups of 3 characters of 'rwx' (read, write, execute). If I want to add execute rights to this file I would execute chmod 755 readme.txt
and that permissions portion would become rwxr-xr-x
. I can now execute this file if I want to by running ./readme.txt
(./ tells the bash to look in the current directory for the intended command rather that search the $PATH variable).
schluchc alludes to looking at the man page for chmod, do this by running man chmod
. This is the best way to get documentation on a given command, man <command>
Using json_encode on objects in PHP (regardless of scope)
I usually include a small function in my objects which allows me to dump to array or json or xml. Something like:
public function exportObj($method = 'a')
{
if($method == 'j')
{
return json_encode(get_object_vars($this));
}
else
{
return get_object_vars($this);
}
}
either way, get_object_vars()
is probably useful to you.
SQL Statement using Where clause with multiple values
SELECT PersonName, songName, status
FROM table
WHERE name IN ('Holly', 'Ryan')
If you are using parametrized Stored procedure:
- Pass in comma separated string
- Use special function to split comma separated string into table value variable
- Use
INNER JOIN ON t.PersonName = newTable.PersonName
using a table variable which contains passed in names
How to pass a type as a method parameter in Java
If you want to pass the type, than the equivalent in Java would be
java.lang.Class
If you want to use a weakly typed method, then you would simply use
java.lang.Object
and the corresponding operator
instanceof
e.g.
private void foo(Object o) {
if(o instanceof String) {
}
}//foo
However, in Java there are primitive types, which are not classes (i.e. int from your example), so you need to be careful.
The real question is what you actually want to achieve here, otherwise it is difficult to answer:
Or is there a better way?
How to show an alert box in PHP?
Try this:
Define a funciton:
<?php
function phpAlert($msg) {
echo '<script type="text/javascript">alert("' . $msg . '")</script>';
}
?>
Call it like this:
<?php phpAlert( "Hello world!\\n\\nPHP has got an Alert Box" ); ?>
Find a file with a certain extension in folder
Look at the System.IO.Directory
class and the static method GetFiles
. It has an overload that accepts a path and a search pattern. Example:
string[] files = System.IO.Directory.GetFiles(path, "*.txt");
How to save a dictionary to a file?
As Pickle has some security concerns and is slow (source), I would go for JSON, as it is fast, built-in, human-readable, and interchangeable:
import json
data = {'another_dict': {'a': 0, 'b': 1}, 'a_list': [0, 1, 2, 3]}
# e.g. file = './data.json'
with open(file, 'w') as f:
json.dump(data, f)
Reading is similar easy:
with open(file, 'r') as f:
data = json.load(f)
This is similar to this answer, but implements the file handling correctly.
SQL Server IIF vs CASE
IIF
is the same as CASE WHEN <Condition> THEN <true part> ELSE <false part> END
. The query plan will be the same. It is, perhaps, "syntactical sugar" as initially implemented.
CASE is portable across all SQL platforms whereas IIF is SQL SERVER 2012+ specific.
Load local javascript file in chrome for testing?
To load local resources in Chrome when just using your local computer and not using a webserver you need to add the --allow-file-access-from-files flag.
You can have a shortcut to Chrome that allows files access and one that does not.
Create a shortcut for Chrome on the desktop, right click on shortcut, select properties. In the dialog box that opens find the target for the short cut and add the parameter after chrome.exe leaving a space
eg C:\PATH TO\chrome.exe --allow-file-access-from-files
This shortcut will allow access to files without affecting any other shortcut to Chrome you have.
When you open Chrome with this shortcut it should allow local resources to be loaded using HTML5 and the filesystem api
Apply global variable to Vuejs
If the global variable should not be written to by anything, including Vuejs, you can use Object.freeze
to freeze your object. Adding it to Vue's viewmodel won't unfreeze it.
Another option is to provide Vuejs with a frozen copy of the object, if the object is intended to be written globally but just not by Vue: var frozenCopy = Object.freeze(Object.assign({}, globalObject))
detect key press in python?
As OP mention about raw_input - that means he want cli solution.
Linux: curses is what you want (windows PDCurses). Curses, is an graphical API for cli software, you can achieve more than just detect key events.
This code will detect keys until new line is pressed.
import curses
import os
def main(win):
win.nodelay(True)
key=""
win.clear()
win.addstr("Detected key:")
while 1:
try:
key = win.getkey()
win.clear()
win.addstr("Detected key:")
win.addstr(str(key))
if key == os.linesep:
break
except Exception as e:
# No input
pass
curses.wrapper(main)
Sending and receiving data over a network using TcpClient
First, I recommend that you use WCF, .NET Remoting, or some other higher-level communication abstraction. The learning curve for "simple" sockets is nearly as high as WCF, because there are so many non-obvious pitfalls when using TCP/IP directly.
If you decide to continue down the TCP/IP path, then review my .NET TCP/IP FAQ, particularly the sections on message framing and application protocol specifications.
Also, use asynchronous socket APIs. The synchronous APIs do not scale and in some error situations may cause deadlocks. The synchronous APIs make for pretty little example code, but real-world production-quality code uses the asynchronous APIs.
notifyDataSetChanged example
For an ArrayAdapter
, notifyDataSetChanged
only works if you use the add()
, insert()
, remove()
, and clear()
on the Adapter.
When an ArrayAdapter
is constructed, it holds the reference for the List
that was passed in. If you were to pass in a List
that was a member of an Activity, and change that Activity member later, the ArrayAdapter
is still holding a reference to the original List
. The Adapter does not know you changed the List
in the Activity.
Your choices are:
- Use the functions of the
ArrayAdapter
to modify the underlying List (add()
, insert()
, remove()
, clear()
, etc.)
- Re-create the
ArrayAdapter
with the new List
data. (Uses a lot of resources and garbage collection.)
- Create your own class derived from
BaseAdapter
and ListAdapter
that allows changing of the underlying List
data structure.
- Use the
notifyDataSetChanged()
every time the list is updated. To call it on the UI-Thread, use the runOnUiThread()
of Activity
.
Then, notifyDataSetChanged()
will work.
Left-pad printf with spaces
I use this function to indent my output (for example to print a tree structure). The indent
is the number of spaces before the string.
void print_with_indent(int indent, char * string)
{
printf("%*s%s", indent, "", string);
}
Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected]
Wanted to share what caused the error in my case. Spend couple hours to figure this out, so hopefully it will help to save someone some time.
Strangely enough, the error was raised with the Enable drop directory quota
setting being enabled for the domain.
I am not the expert and don't know the technical explanation, but unticking the mentioned setting sorted the problem.
How to detect Safari, Chrome, IE, Firefox and Opera browser?
Here's a 2016 adjusted version of Rob's answer, including Microsoft Edge and detection of Blink:
(edit: I updated Rob's answer above with this information.)
_x000D_
_x000D_
// Opera 8.0+ (UA detection to detect Blink/v8-powered Opera)_x000D_
isOpera = !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;_x000D_
// Firefox 1.0+_x000D_
isFirefox = typeof InstallTrigger !== 'undefined';_x000D_
// Safari 3.0+_x000D_
isSafari = /constructor/i.test(window.HTMLElement) || (function (p) { return p.toString() === "[object SafariRemoteNotification]"; })(!window['safari'] || safari.pushNotification);_x000D_
// Internet Explorer 6-11_x000D_
isIE = /*@cc_on!@*/false || !!document.documentMode;_x000D_
// Edge 20+_x000D_
isEdge = !isIE && !!window.StyleMedia;_x000D_
// Chrome 1+_x000D_
isChrome = !!window.chrome && !!window.chrome.webstore;_x000D_
// Blink engine detection_x000D_
isBlink = (isChrome || isOpera) && !!window.CSS;_x000D_
_x000D_
/* Results: */_x000D_
console.log("isOpera", isOpera);_x000D_
console.log("isFirefox", isFirefox);_x000D_
console.log("isSafari", isSafari);_x000D_
console.log("isIE", isIE);_x000D_
console.log("isEdge", isEdge);_x000D_
console.log("isChrome", isChrome);_x000D_
console.log("isBlink", isBlink);
_x000D_
_x000D_
_x000D_
The beauty of this approach is that it relies on browser engine properties, so it covers even derivative browsers, such as Yandex or Vivaldi, which are practically compatible with the major browsers whose engines they use. The exception is Opera, which relies on user agent sniffing, but today (i.e. ver. 15 and up) even Opera is itself only a shell for Blink.
Using multiple case statements in select query
There are two ways to write case statements, you seem to be using a combination of the two
case a.updatedDate
when 1760 then 'Entered on' + a.updatedDate
when 1710 then 'Viewed on' + a.updatedDate
else 'Last Updated on' + a.updateDate
end
or
case
when a.updatedDate = 1760 then 'Entered on' + a.updatedDate
when a.updatedDate = 1710 then 'Viewed on' + a.updatedDate
else 'Last Updated on' + a.updateDate
end
are equivalent. They may not work because you may need to convert date types to varchars to append them to other varchars.
How to redirect to another page in node.js
The If else statement needs to be wrapped in a .get or a .post to redirect. Such as
app.post('/login', function(req, res) {
});
or
app.get('/login', function(req, res) {
});
Styling twitter bootstrap buttons
You can overwrite the colors in your css, for example for Danger button:
.btn-danger { border-color: #[insert color here]; background-color: #[insert color here];
.btn-danger:hover { border-color: #[insert color here]; background-color: #[insert color here]; }
Copying PostgreSQL database to another server
You don't need to create an intermediate file. You can do
pg_dump -C -h localhost -U localuser dbname | psql -h remotehost -U remoteuser dbname
or
pg_dump -C -h remotehost -U remoteuser dbname | psql -h localhost -U localuser dbname
using psql
or pg_dump
to connect to a remote host.
With a big database or a slow connection, dumping a file and transfering the file compressed may be faster.
As Kornel said there is no need to dump to a intermediate file, if you want to work compressed you can use a compressed tunnel
pg_dump -C dbname | bzip2 | ssh remoteuser@remotehost "bunzip2 | psql dbname"
or
pg_dump -C dbname | ssh -C remoteuser@remotehost "psql dbname"
but this solution also requires to get a session in both ends.
Note: pg_dump
is for backing up and psql
is for restoring. So, the first command in this answer is to copy from local to remote and the second one is from remote to local. More -> https://www.postgresql.org/docs/9.6/app-pgdump.html
Global npm install location on windows?
These are typical npm paths if you install a package globally:
Windows XP - %USERPROFILE%\Application Data\npm\node_modules
Newer Windows Versions - %AppData%\npm\node_modules
or - %AppData%\roaming\npm\node_modules
Should __init__() call the parent class's __init__()?
If you need something from super's __init__
to be done in addition to what is being done in the current class's __init__,
you must call it yourself, since that will not happen automatically. But if you don't need anything from super's __init__,
no need to call it. Example:
>>> class C(object):
def __init__(self):
self.b = 1
>>> class D(C):
def __init__(self):
super().__init__() # in Python 2 use super(D, self).__init__()
self.a = 1
>>> class E(C):
def __init__(self):
self.a = 1
>>> d = D()
>>> d.a
1
>>> d.b # This works because of the call to super's init
1
>>> e = E()
>>> e.a
1
>>> e.b # This is going to fail since nothing in E initializes b...
Traceback (most recent call last):
File "<pyshell#70>", line 1, in <module>
e.b # This is going to fail since nothing in E initializes b...
AttributeError: 'E' object has no attribute 'b'
__del__
is the same way, (but be wary of relying on __del__
for finalization - consider doing it via the with statement instead).
I rarely use __new__.
I do all the initialization in __init__.
Angular 2 'component' is not a known element
I had the same problem with Angular CLI: 10.1.5
The code works fine, but the error was shown in the VScode v1.50
Resolved by killing the terminal (ng serve) and restarting VScode.
Updates were rejected because the tip of your current branch is behind its remote counterpart
This just happened to me.
- I made a pull request to our master yesterday.
- My colleague was reviewing it today and saw that it was out of sync with our master branch, so with the intention of helping me, he merged master to my branch.
- I didn't know he did that.
- Then I merged master locally, tried to push it, but it failed. Why? Because my colleague merge with master created an extra commit I did not have locally!
Solution: Pull down my own branch so I get that extra commit. Then push it back to my remote branch.
literally what I did on my branch was:
git pull
git push
Multiple separate IF conditions in SQL Server
Maybe this is a bit redundant, but no one appeared to have mentioned this as a solution.
As a beginner in SQL I find that when using a BEGIN
and END
SSMS usually adds a squiggly line with incorrect syntax near 'END'
to END, simply because there's no content in between yet. If you're just setting up BEGIN
and END
to get started and add the actual query later, then simply add a bogus PRINT
statement so SSMS stops bothering you.
For example:
IF (1=1)
BEGIN
PRINT 'BOGUS'
END
The following will indeed set you on the wrong track, thinking you made a syntax error which in this case just means you still need to add content in between BEGIN and END:
IF (1=1)
BEGIN
END
How to display list of repositories from subversion server
If you know your way around Java, you can use SvnKit to do browse, search and God knows what with your Subversion server.
After that, you can package your program and invoke it either via an Ant task or a shell script.
It's quite a "brute force" solution, but once you master SvnKit, you can really do lots of cool things.
How to search a string in String array
You can use Find method of Array type. From .NET 3.5 and higher.
public static T Find<T>(
T[] array,
Predicate<T> match
)
Here is some examples:
// we search an array of strings for a name containing the letter “a”:
static void Main()
{
string[] names = { "Rodney", "Jack", "Jill" };
string match = Array.Find (names, ContainsA);
Console.WriteLine (match); // Jack
}
static bool ContainsA (string name) { return name.Contains ("a"); }
Here’s the same code shortened with an anonymous method:
string[] names = { "Rodney", "Jack", "Jill" };
string match = Array.Find (names, delegate (string name)
{ return name.Contains ("a"); } ); // Jack
A lambda expression shortens it further:
string[] names = { "Rodney", "Jack", "Jill" };
string match = Array.Find (names, n => n.Contains ("a")); // Jack
How to convert string to binary?
def method_a(sample_string):
binary = ' '.join(format(ord(x), 'b') for x in sample_string)
def method_b(sample_string):
binary = ' '.join(map(bin,bytearray(sample_string,encoding='utf-8')))
if __name__ == '__main__':
from timeit import timeit
sample_string = 'Convert this ascii strong to binary.'
print(
timeit(f'method_a("{sample_string}")',setup='from __main__ import method_a'),
timeit(f'method_b("{sample_string}")',setup='from __main__ import method_b')
)
# 9.564299999998184 2.943955828988692
method_b is substantially more efficient at converting to a byte array because it makes low level function calls instead of manually transforming every character to an integer, and then converting that integer into its binary value.
cURL POST command line on WINDOWS RESTful service
We can use below Curl command in Windows Command prompt to send the request.
Use the Curl command below, replace single quote with double quotes, remove quotes where they are not there in below format and use the ^
symbol.
curl http://localhost:7101/module/url ^
-d @D:/request.xml ^
-H "Content-Type: text/xml" ^
-H "SOAPAction: process" ^
-H "Authorization: Basic xyz" ^
-X POST
2 column div layout: right column with fixed width, left fluid
This is a generic, HTML source ordered solution where:
- The first column in source order is fluid
- The second column in source order is fixed
- This column can be floated left or right using CSS
Fixed/Second Column on Right
_x000D_
_x000D_
#wrapper {_x000D_
margin-right: 200px;_x000D_
}_x000D_
#content {_x000D_
float: left;_x000D_
width: 100%;_x000D_
background-color: powderblue;_x000D_
}_x000D_
#sidebar {_x000D_
float: right;_x000D_
width: 200px;_x000D_
margin-right: -200px;_x000D_
background-color: palevioletred;_x000D_
}_x000D_
#cleared {_x000D_
clear: both;_x000D_
}
_x000D_
<div id="wrapper">_x000D_
<div id="content">Column 1 (fluid)</div>_x000D_
<div id="sidebar">Column 2 (fixed)</div>_x000D_
<div id="cleared"></div>_x000D_
</div>
_x000D_
_x000D_
_x000D_
Fixed/Second Column on Left
_x000D_
_x000D_
#wrapper {_x000D_
margin-left: 200px;_x000D_
}_x000D_
#content {_x000D_
float: right;_x000D_
width: 100%;_x000D_
background-color: powderblue;_x000D_
}_x000D_
#sidebar {_x000D_
float: left;_x000D_
width: 200px;_x000D_
margin-left: -200px;_x000D_
background-color: palevioletred;_x000D_
}_x000D_
#cleared {_x000D_
clear: both;_x000D_
}
_x000D_
<div id="wrapper">_x000D_
<div id="content">Column 1 (fluid)</div>_x000D_
<div id="sidebar">Column 2 (fixed)</div>_x000D_
<div id="cleared"></div>_x000D_
</div>
_x000D_
_x000D_
_x000D_
Alternate solution is to use display: table-cell; which results in equal height columns.
Java check if boolean is null
boolean
is a primitive type, and therefore can not be null.
Its boxed type, Boolean
, can be null.
The function is probably returning a Boolean
as opposed to a boolean
, so assigning the result to a Boolean
-type variable will allow you to test for nullity.
How to check if a directory containing a file exist?
EDIT: as of Java8 you'd better use Files
class:
Path resultingPath = Files.createDirectories('A/B');
I don't know if this ultimately fixes your problem but class File
has method mkdirs()
which fully creates the path specified by the file.
File f = new File("/A/B/");
f.mkdirs();
What does if [ $? -eq 0 ] mean for shell scripts?
It's checking the return value ($?
) of grep
. In this case it's comparing it to 0 (success).
Usually when you see something like this (checking the return value of grep) it's checking to see whether the particular string was detected. Although the redirect to /dev/null
isn't necessary, the same thing can be accomplished using -q
.
What is the use of printStackTrace() method in Java?
printStackTrace()
prints the locations where the exception occurred in the source code, thus allowing the author who wrote the program to see what went wrong. But since it shows problems in the source code, the user(s) who may or may not have any coding experience may not be able to understand what went wrong, so if the program allows the user to send error messages to the authors, the users may not be able to give good data on what went wrong.
You should consider the Logger.getLogger()
method, it offers a better exception handling (logging) facility, and besides printStackTrace()
without arguments is considered to be obsolete and should ONLY be used for debugging purposes, not for user display.
Authentication issues with WWW-Authenticate: Negotiate
The web server is prompting you for a SPNEGO (Simple and Protected GSSAPI Negotiation Mechanism) token.
This is a Microsoft invention for negotiating a type of authentication to use for Web SSO (single-sign-on):
See:
Oracle insert if not exists statement
insert into OPT (email, campaign_id)
select 'mom@coxnet' as email, 100 as campaign_id from dual MINUS
select email, campaign_id from OPT;
If there is already a record with [email protected]
/100
in OPT, the MINUS
will subtract this record from the select 'mom@coxnet' as email, 100 as campaign_id from dual
record and nothing will be inserted. On the other hand, if there is no such record, the MINUS
does not subract anything and the values mom@coxnet
/100
will be inserted.
As p.marino has already pointed out, merge
is probably the better (and more correct) solution for your problem as it is specifically designed to solve your task.
Create folder in Android
If you are trying to make more than just one folder on the root of the sdcard,
ex. Environment.getExternalStorageDirectory() + "/Example/Ex App/"
then instead of folder.mkdir()
you would use folder.mkdirs()
I've made this mistake in the past & I took forever to figure it out.
Alter a MySQL column to be AUTO_INCREMENT
You can use the following query to make document_id to increment automatically
ALTER TABLE document MODIFY COLUMN document_id INT auto_increment
It is preferred to make document_id primary key as well
ALTER TABLE document MODIFY COLUMN document_id INT auto_increment PRIMARY KEY;
C# Connecting Through Proxy
Foole's code worked perfectly for me, but in .NET 4.0, don't forget to check if Proxy is NULL, which means no proxy configured (outside corporate environment)
So here's the code that solved my problem with our corporate proxy
WebClient web = new WebClient();
if (web.Proxy != null)
web.Proxy.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
Radio button checked event handling
Update in 2017: Hey. This is a terrible answer. Don't use it. Back in the old days this type of jQuery use was common. And it probably worked back then. Just read it, realize it's terrible, then move on (or downvote or, whatever) to one of the other answers that are better for today's jQuery.
$("input[type=radio]").change(function(){
alert( $("input[type=radio][name="+ this.name + "]").val() );
});
How to find locked rows in Oracle
Look at the dba_blockers
, dba_waiters
and dba_locks
for locking. The names should be self explanatory.
You could create a job that runs, say, once a minute and logged the values in the dba_blockers
and the current active sql_id
for that session. (via v$session
and v$sqlstats
).
You may also want to look in v$sql_monitor
. This will be default log all SQL that takes longer than 5 seconds. It is also visible on the "SQL Monitoring" page in Enterprise Manager.
How do you split and unsplit a window/view in Eclipse IDE?
This is possible with the menu items Window>Editor>Toggle Split Editor.
Current shortcut for splitting is:
Azerty keyboard:
- Ctrl + _ for split horizontally, and
- Ctrl + { for split vertically.
Qwerty US keyboard:
- Ctrl + Shift + - (accessing _) for split horizontally, and
- Ctrl + Shift + [ (accessing {) for split vertically.
MacOS - Qwerty US keyboard:
- ⌘ + Shift + - (accessing _) for split horizontally, and
- ⌘ + Shift + [ (accessing {) for split vertically.
On any other keyboard if a required key is unavailable (like { on a german Qwertz keyboard), the following generic approach may work:
- Alt + ASCII code + Ctrl then release Alt
Example: ASCII for '{' = 123, so press 'Alt', '1', '2', '3', 'Ctrl' and release 'Alt', effectively typing '{' while 'Ctrl' is pressed, to split vertically.
Example of vertical split:
PS:
- The menu items Window>Editor>Toggle Split Editor were added with Eclipse Luna 4.4 M4, as mentioned by Lars Vogel in "Split editor implemented in Eclipse M4 Luna"
- The split editor is one of the oldest and most upvoted Eclipse bug! Bug 8009
- The split editor functionality has been developed in Bug 378298, and will be available as of Eclipse Luna M4. The Note & Newsworthy of Eclipse Luna M4 will contain the announcement.
Extracting time from POSIXct
Many solutions have been provided, but I have not seen this one, which uses package chron:
hours = times(strftime(times, format="%T"))
plot(val~hours)
(sorry, I am not entitled to post an image, you'll have to plot it yourself)
Firebase Storage How to store and Retrieve images
Yes, you can store and view images in Firebase. You can use a filepicker to get the image file. Then you can host the image however you want, I prefer Amazon s3. Once the image is hosted you can display the image using the URL generated for the image.
Hope this helps.
Abstraction VS Information Hiding VS Encapsulation
I too was very confused about the two concepts of Abstraction and Encapsulation. But when I saw the abstraction article on myjavatrainer.com, It became clear to me that Abstraction and Encapsulation are Apples and Oranges, you can't really compare them because both are required.
Encapsulation is how the object is created, and abstraction is how the object is viewed in the outside world.
Setting up Eclipse with JRE Path
Add the following to the eclipse.ini
:
-vm
Java_Home_Variable\bin\javaw.exe
In my Case its
-vm
H:\usr\java\jdk1.6.0_16\bin\javaw.exe
C# static class constructor
We can create static constructor
static class StaticParent
{
StaticParent()
{
//write your initialization code here
}
}
and it is always parameter less.
static class StaticParent
{
static int i =5;
static StaticParent(int i) //Gives error
{
//write your initialization code here
}
}
and it doesn't have the access modifier
How to compare if two structs, slices or maps are equal?
reflect.DeepEqual
is often incorrectly used to compare two like structs, as in your question.
cmp.Equal
is a better tool for comparing structs.
To see why reflection is ill-advised, let's look at the documentation:
Struct values are deeply equal if their corresponding fields, both exported and unexported, are deeply equal.
....
numbers, bools, strings, and channels - are deeply equal if they are equal using Go's == operator.
If we compare two time.Time
values of the same UTC time, t1 == t2
will be false if their metadata timezone is different.
go-cmp
looks for the Equal()
method and uses that to correctly compare times.
Example:
m1 := map[string]int{
"a": 1,
"b": 2,
}
m2 := map[string]int{
"a": 1,
"b": 2,
}
fmt.Println(cmp.Equal(m1, m2)) // will result in true
Read an Excel file directly from a R script
Yes. See the relevant page on the R wiki. Short answer: read.xls
from the gdata
package works most of the time (although you need to have Perl installed on your system -- usually already true on MacOS and Linux, but takes an extra step on Windows, i.e. see http://strawberryperl.com/). There are various caveats, and alternatives, listed on the R wiki page.
The only reason I see not to do this directly is that you may want to examine the spreadsheet to see if it has glitches (weird headers, multiple worksheets [you can only read one at a time, although you can obviously loop over them all], included plots, etc.). But for a well-formed, rectangular spreadsheet with plain numbers and character data (i.e., not comma-formatted numbers, dates, formulas with divide-by-zero errors, missing values, etc. etc. ..) I generally have no problem with this process.
How to change line width in IntelliJ (from 120 character)
You can alter the "Right margin" attribute in the preferences, which can be found via
File | Settings | Project Settings | Code Style - General
Right Margin (columns) In this text box, specify the number of columns
to be used to display pages in the editor.
Source: Jetbrains
How to change the Jupyter start-up folder
First try to run
jupyter notebook --notebook-dir="C:/Your/Desired/Start/Directory/"
in a command line (cmd) to see if the Jupyter notebook opens at the desired location.
If yes, then you can make it a shortcut by:
In a Windows File Explorer or on the desktop, Right click > New > Shortcut
Enter the following location and click next:
jupyter notebook --notebook-dir="C:/Your/Desired/Start/Directory/"
- Enter a name for your shortcut and finish
Now you have a shortcut to start Jupyter at the location you want. This works on Windows 7, macOS, and Linux.
For windows best to enclose the path in double quotes "
as single quotes '
will not work if there is a space in the pathname
Note if you found the error saying the path is not valid, try using common slash /
instead of backslash \
in the path like
jupyter notebook --notebook-dir="D:/"
Attempt to write a readonly database - Django w/ SELinux error
You have to add writing rights to the directory in which your sqlite database is stored. So running chmod 664 /srv/mysite
should help.
This is a security risk, so better solution is to change the owner of your database to www-data
:
chown www-data:www-data /srv/mysite
chown www-data:www-data /srv/mysite/DATABASE.sqlite
Undoing a git rebase
If you don't want to do a hard reset...
You can checkout the commit from the reflog, and then save it as a new branch:
git reflog
Find the commit just before you started rebasing. You may need to scroll further down to find it (press Enter or PageDown). Take note of the HEAD number and replace 57:
git checkout HEAD@{57}
Review the branch/commits, and if it's correct then create a new branch using this HEAD:
git checkout -b new_branch_name
Difference between h:button and h:commandButton
Here is what the JSF javadocs have to say about the commandButton
action
attribute:
MethodExpression representing the application action to invoke when
this component is activated by the user. The expression must evaluate
to a public method that takes no parameters, and returns an Object
(the toString() of which is called to derive the logical outcome)
which is passed to the NavigationHandler for this application.
It would be illuminating to me if anyone can explain what that has to do with any of the answers on this page. It seems pretty clear that action
refers to some page's filename and not a method.
How to make readonly all inputs in some div in Angular2?
You can do like this.
Open a ts file ad there make an interface with inputs you want and in the page you want to show under export class write
readonly yourinterface = yourinterface
readonly level: number[] = [];
and in your template do like this
*ngFor="let yourtype of yourinterface"
React.js: onChange event for contentEditable
This probably isn't exactly the answer you're looking for, but having struggled with this myself and having issues with suggested answers, I decided to make it uncontrolled instead.
When editable
prop is false
, I use text
prop as is, but when it is true
, I switch to editing mode in which text
has no effect (but at least browser doesn't freak out). During this time onChange
are fired by the control. Finally, when I change editable
back to false
, it fills HTML with whatever was passed in text
:
/** @jsx React.DOM */
'use strict';
var React = require('react'),
escapeTextForBrowser = require('react/lib/escapeTextForBrowser'),
{ PropTypes } = React;
var UncontrolledContentEditable = React.createClass({
propTypes: {
component: PropTypes.func,
onChange: PropTypes.func.isRequired,
text: PropTypes.string,
placeholder: PropTypes.string,
editable: PropTypes.bool
},
getDefaultProps() {
return {
component: React.DOM.div,
editable: false
};
},
getInitialState() {
return {
initialText: this.props.text
};
},
componentWillReceiveProps(nextProps) {
if (nextProps.editable && !this.props.editable) {
this.setState({
initialText: nextProps.text
});
}
},
componentWillUpdate(nextProps) {
if (!nextProps.editable && this.props.editable) {
this.getDOMNode().innerHTML = escapeTextForBrowser(this.state.initialText);
}
},
render() {
var html = escapeTextForBrowser(this.props.editable ?
this.state.initialText :
this.props.text
);
return (
<this.props.component onInput={this.handleChange}
onBlur={this.handleChange}
contentEditable={this.props.editable}
dangerouslySetInnerHTML={{__html: html}} />
);
},
handleChange(e) {
if (!e.target.textContent.trim().length) {
e.target.innerHTML = '';
}
this.props.onChange(e);
}
});
module.exports = UncontrolledContentEditable;
In SQL Server, how to create while loop in select
- Create function that parses incoming string (say "AABBCC") as a table of strings (in particular "AA", "BB", "CC").
- Select IDs from your table and use CROSS APPLY the function with data as argument so you'll have as many rows as values contained in the current row's data. No need of cursors or stored procs.
Debian 8 (Live-CD) what is the standard login and password?
Although this is an old question, I had the same question when using the Standard console version. The answer can be found in the Debian Live manual under the section 10.1 Customizing the live user. It says:
It is also possible to change the default username "user" and the
default password "live".
I tried the username user
and password live
and it did work. If you want to run commands as root you can preface each command with sudo
Generate class from database table
A small addition to the solutions before:
object_id(@TableName)
works only if you are in the default schema.
(Select id from sysobjects where name = @TableName)
works in any schema provided @tableName is unique.
Can't import org.apache.http.HttpResponse in Android Studio
HttpClient was deprecated in Android 5.1 and is removed from the Android SDK in Android 6.0. While there is a workaround to continue using HttpClient in Android 6.0 with Android Studio, you really need to move to something else. That "something else" could be:
Or, depending upon the nature of your HTTP work, you might choose a library that supports higher-order operations (e.g., Retrofit for Web service APIs).
In a pinch, you could enable the legacy APIs, by having useLibrary 'org.apache.http.legacy'
in your android
closure in your module's build.gradle
file. However, Google has been advising people for years to stop using Android's built-in HttpClient, and so at most, this should be a stop-gap move, while you work on a more permanent shift to another API.
How to find a min/max with Ruby
In addition to the provided answers, if you want to convert Enumerable#max into a max method that can call a variable number or arguments, like in some other programming languages, you could write:
def max(*values)
values.max
end
Output:
max(7, 1234, 9, -78, 156)
=> 1234
This abuses the properties of the splat operator to create an array object containing all the arguments provided, or an empty array object if no arguments were provided. In the latter case, the method will return nil
, since calling Enumerable#max on an empty array object returns nil
.
If you want to define this method on the Math module, this should do the trick:
module Math
def self.max(*values)
values.max
end
end
Note that Enumerable.max is, at least, two times slower compared to the ternary operator (?:
). See Dave Morse's answer for a simpler and faster method.
How to make two plots side-by-side using Python?
You can use - matplotlib.gridspec.GridSpec
Check - https://matplotlib.org/stable/api/_as_gen/matplotlib.gridspec.GridSpec.html
The below code displays a heatmap on right and an Image on left.
#Creating 1 row and 2 columns grid
gs = gridspec.GridSpec(1, 2)
fig = plt.figure(figsize=(25,3))
#Using the 1st row and 1st column for plotting heatmap
ax=plt.subplot(gs[0,0])
ax=sns.heatmap([[1,23,5,8,5]],annot=True)
#Using the 1st row and 2nd column to show the image
ax1=plt.subplot(gs[0,1])
ax1.grid(False)
ax1.set_yticklabels([])
ax1.set_xticklabels([])
#The below lines are used to display the image on ax1
image = io.imread("https://images-na.ssl-images- amazon.com/images/I/51MvhqY1qdL._SL160_.jpg")
plt.imshow(image)
plt.show()
Output image
Html ordered list 1.1, 1.2 (Nested counters and scope) not working
Moshe's solution is great but the problem may still exist if you need to put the list inside a div
. (read: CSS counter-reset on nested list)
This style could prevent that issue:
_x000D_
_x000D_
ol > li {_x000D_
counter-increment: item;_x000D_
}_x000D_
_x000D_
ol > li:first-child {_x000D_
counter-reset: item;_x000D_
}_x000D_
_x000D_
ol ol > li {_x000D_
display: block;_x000D_
}_x000D_
_x000D_
ol ol > li:before {_x000D_
content: counters(item, ".") ". ";_x000D_
margin-left: -20px;_x000D_
}
_x000D_
<ol>_x000D_
<li>list not nested in div</li>_x000D_
</ol>_x000D_
_x000D_
<hr>_x000D_
_x000D_
<div>_x000D_
<ol>_x000D_
<li>nested in div</li>_x000D_
<li>two_x000D_
<ol>_x000D_
<li>two.one</li>_x000D_
<li>two.two</li>_x000D_
<li>two.three</li>_x000D_
</ol>_x000D_
</li>_x000D_
<li>three_x000D_
<ol>_x000D_
<li>three.one</li>_x000D_
<li>three.two_x000D_
<ol>_x000D_
<li>three.two.one</li>_x000D_
<li>three.two.two</li>_x000D_
</ol>_x000D_
</li>_x000D_
</ol>_x000D_
</li>_x000D_
<li>four</li>_x000D_
</ol>_x000D_
</div>
_x000D_
_x000D_
_x000D_
You can also set the counter-reset on li:before
.
Confused about stdin, stdout and stderr?
stderr will not do IO Cache buffering so if our application need to print critical message info (some errors ,exceptions) to console or to file use it where as use stdout to print general log info as it use IO Cache buffering there is a chance that before writing our messages to file application may close ,leaving debugging complex