Is there a better way than the following to check to see if a string is nil OR has a length of 0 in Ruby?
if !my_string || my_string.length == 0
return true
else
return false
end
In C# there's the handy
string.IsNullOrEmpty(myString)
Anything similar to that in Ruby?
This question is related to
ruby
First of all, beware of that method:
As Jesse Ezel says:
"The method might seem convenient, but most of the time I have found that this situation arises from trying to cover up deeper bugs.
Your code should stick to a particular protocol on the use of strings, and you should understand the use of the protocol in library code and in the code you are working with.
The NullOrEmpty protocol is typically a quick fix (so the real problem is still somewhere else, and you got two protocols in use) or it is a lack of expertise in a particular protocol when implementing new code (and again, you should really know what your return values are)."
And if you patch String class... be sure NilClass has not been patch either!
class NilClass
def empty?; true; end
end
An alternative to jcoby's proposal would be:
class NilClass
def nil_or_empty?
true
end
end
class String
def nil_or_empty?
empty?
end
end
If you are willing to require ActiveSupport you can just use the #blank?
method, which is defined for both NilClass and String.
In rails you can try #blank?
.
Warning: it will give you positives when string consists of spaces:
nil.blank? # ==> true
''.blank? # ==> true
' '.blank? # ==> true
'false'.blank? # ==> false
Just wanted to point it out. Maybe it suits your needs
UPD. why am i getting old questions in my feed? Sorry for necroposting.
Another option is to convert nil to an empty result on the fly:
(my_string||'').empty?
As it was said here before Rails (ActiveSupport) have a handy blank? method and it is implemented like this:
class Object
def blank?
respond_to?(:empty?) ? empty? : !self
end
end
Pretty easy to add to any ruby-based project.
The beauty of this solution is that it works auto-magicaly not only for Strings but also for Arrays and other types.
Konrad Rudolph has the right answer.
If it really bugs you, monkey patch the String class or add it to a class/module of your choice. It's really not a good practice to monkey patch core objects unless you have a really compelling reason though.
class String
def self.nilorempty?(string)
string.nil? || string.empty?
end
end
Then you can do String.nilorempty? mystring
If you are willing to require ActiveSupport you can just use the #blank?
method, which is defined for both NilClass and String.
First of all, beware of that method:
As Jesse Ezel says:
"The method might seem convenient, but most of the time I have found that this situation arises from trying to cover up deeper bugs.
Your code should stick to a particular protocol on the use of strings, and you should understand the use of the protocol in library code and in the code you are working with.
The NullOrEmpty protocol is typically a quick fix (so the real problem is still somewhere else, and you got two protocols in use) or it is a lack of expertise in a particular protocol when implementing new code (and again, you should really know what your return values are)."
And if you patch String class... be sure NilClass has not been patch either!
class NilClass
def empty?; true; end
end
I like to do this as follows (in a non Rails/ActiveSupport environment):
variable.to_s.empty?
this works because:
nil.to_s == ""
"".to_s == ""
As it was said here before Rails (ActiveSupport) have a handy blank? method and it is implemented like this:
class Object
def blank?
respond_to?(:empty?) ? empty? : !self
end
end
Pretty easy to add to any ruby-based project.
The beauty of this solution is that it works auto-magicaly not only for Strings but also for Arrays and other types.
First of all, beware of that method:
As Jesse Ezel says:
"The method might seem convenient, but most of the time I have found that this situation arises from trying to cover up deeper bugs.
Your code should stick to a particular protocol on the use of strings, and you should understand the use of the protocol in library code and in the code you are working with.
The NullOrEmpty protocol is typically a quick fix (so the real problem is still somewhere else, and you got two protocols in use) or it is a lack of expertise in a particular protocol when implementing new code (and again, you should really know what your return values are)."
And if you patch String class... be sure NilClass has not been patch either!
class NilClass
def empty?; true; end
end
If you are willing to require ActiveSupport you can just use the #blank?
method, which is defined for both NilClass and String.
First of all, beware of that method:
As Jesse Ezel says:
"The method might seem convenient, but most of the time I have found that this situation arises from trying to cover up deeper bugs.
Your code should stick to a particular protocol on the use of strings, and you should understand the use of the protocol in library code and in the code you are working with.
The NullOrEmpty protocol is typically a quick fix (so the real problem is still somewhere else, and you got two protocols in use) or it is a lack of expertise in a particular protocol when implementing new code (and again, you should really know what your return values are)."
And if you patch String class... be sure NilClass has not been patch either!
class NilClass
def empty?; true; end
end
variable.blank? will do it. It returns true if the string is empty or if the string is nil.
An alternative to jcoby's proposal would be:
class NilClass
def nil_or_empty?
true
end
end
class String
def nil_or_empty?
empty?
end
end
nil?
can be omitted in boolean contexts. Generally, you can use this to replicate the C# code:
return my_string.nil? || my_string.empty?
Have you tried Refinements?
module Nothingness
refine String do
alias_method :nothing?, :empty?
end
refine NilClass do
alias_method :nothing?, :nil?
end
end
using Nothingness
return my_string.nothing?
Konrad Rudolph has the right answer.
If it really bugs you, monkey patch the String class or add it to a class/module of your choice. It's really not a good practice to monkey patch core objects unless you have a really compelling reason though.
class String
def self.nilorempty?(string)
string.nil? || string.empty?
end
end
Then you can do String.nilorempty? mystring
An alternative to jcoby's proposal would be:
class NilClass
def nil_or_empty?
true
end
end
class String
def nil_or_empty?
empty?
end
end
Another option is to convert nil to an empty result on the fly:
(my_string||'').empty?
If you are using rails, you can use #present?
require 'rails'
nil.present? # ==> false (Works on nil)
''.present? # ==> false (Works on strings)
' '.present? # ==> false (Works on blank strings)
[].present? # ==> false(Works on arrays)
false.present? # ==> false (Works on boolean)
So, conversely to check for nil or zero length use !present?
!(nil.present?) # ==> true
!(''.present?) # ==> true
!(' '.present?) # ==> true
!([].present?) # ==> true
!(false.present?) # ==> true
I like to do this as follows (in a non Rails/ActiveSupport environment):
variable.to_s.empty?
this works because:
nil.to_s == ""
"".to_s == ""
Every class has a nil?
method:
if a_variable.nil?
# the variable has a nil value
end
And strings have the empty?
method:
if a_string.empty?
# the string is empty
}
Remember that a string does not equal nil
when it is empty, so use the empty?
method to check if a string is empty.
nil?
can be omitted in boolean contexts. Generally, you can use this to replicate the C# code:
return my_string.nil? || my_string.empty?
For code golfers:
if my_string=~/./
p 'non-empty string'
else
p 'nil or empty string'
end
Or if you're not a golfer (requires ruby 2.3 or later):
if my_string&.size&.positive?
# nonzero? also works
p 'non-empty string'
else
p 'nil or empty string'
end
If you are willing to require ActiveSupport you can just use the #blank?
method, which is defined for both NilClass and String.
For code golfers:
if my_string=~/./
p 'non-empty string'
else
p 'nil or empty string'
end
Or if you're not a golfer (requires ruby 2.3 or later):
if my_string&.size&.positive?
# nonzero? also works
p 'non-empty string'
else
p 'nil or empty string'
end
nil?
can be omitted in boolean contexts. Generally, you can use this to replicate the C# code:
return my_string.nil? || my_string.empty?
As it was said here before Rails (ActiveSupport) have a handy blank? method and it is implemented like this:
class Object
def blank?
respond_to?(:empty?) ? empty? : !self
end
end
Pretty easy to add to any ruby-based project.
The beauty of this solution is that it works auto-magicaly not only for Strings but also for Arrays and other types.
variable.blank? will do it. It returns true if the string is empty or if the string is nil.
nil?
can be omitted in boolean contexts. Generally, you can use this to replicate the C# code:
return my_string.nil? || my_string.empty?
Every class has a nil?
method:
if a_variable.nil?
# the variable has a nil value
end
And strings have the empty?
method:
if a_string.empty?
# the string is empty
}
Remember that a string does not equal nil
when it is empty, so use the empty?
method to check if a string is empty.
Konrad Rudolph has the right answer.
If it really bugs you, monkey patch the String class or add it to a class/module of your choice. It's really not a good practice to monkey patch core objects unless you have a really compelling reason though.
class String
def self.nilorempty?(string)
string.nil? || string.empty?
end
end
Then you can do String.nilorempty? mystring
In rails you can try #blank?
.
Warning: it will give you positives when string consists of spaces:
nil.blank? # ==> true
''.blank? # ==> true
' '.blank? # ==> true
'false'.blank? # ==> false
Just wanted to point it out. Maybe it suits your needs
UPD. why am i getting old questions in my feed? Sorry for necroposting.
There are some good answers here, but you don't need ActiveSupport or monkey-patching to address the common use case here. For example:
my_string.to_s.empty? if defined? my_string
This will "do the right thing" if my_string is nil or an empty string, but will not raise a NameError exception if my_string is not defined. This is generally preferable to the more contrived:
my_string.to_s.empty? rescue NameError
or its more verbose ilk, because exceptions should really be saved for things you don't expect to happen. In this case, while it might be a common error, an undefined variable isn't really an exceptional circumstance, so it should be handled accordingly.
Your mileage may vary.
If you are using rails, you can use #present?
require 'rails'
nil.present? # ==> false (Works on nil)
''.present? # ==> false (Works on strings)
' '.present? # ==> false (Works on blank strings)
[].present? # ==> false(Works on arrays)
false.present? # ==> false (Works on boolean)
So, conversely to check for nil or zero length use !present?
!(nil.present?) # ==> true
!(''.present?) # ==> true
!(' '.present?) # ==> true
!([].present?) # ==> true
!(false.present?) # ==> true
Every class has a nil?
method:
if a_variable.nil?
# the variable has a nil value
end
And strings have the empty?
method:
if a_string.empty?
# the string is empty
}
Remember that a string does not equal nil
when it is empty, so use the empty?
method to check if a string is empty.
Have you tried Refinements?
module Nothingness
refine String do
alias_method :nothing?, :empty?
end
refine NilClass do
alias_method :nothing?, :nil?
end
end
using Nothingness
return my_string.nothing?
Source: Stackoverflow.com