If I set some nil values to an array, I don't seem to be able to check for them. I have tried any? and empty?.
array = [nil, nil, nil]
#=> [nil, nil, nil]
array[1].any?
#=> "NoMethodError: undefined method `any?' for nil:NilClass"
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6 Answers
any? iterates over a container, like an array, and looks at each element passed to it to see if it passes a test. If one does, the loop stops and true is returned:
ary = [nil, 1]
ary.any?{ |e| e.nil? } # => true
The documentation explains this well:
Passes each element of the collection to the given block. The method returns true if the block ever returns a value other than false or nil. If the block is not given, Ruby adds an implicit block of { |obj| obj } that will cause any? to return true if at least one of the collection members is not false or nil.
%w[ant bear cat].any? { |word| word.length >= 3 } #=> true
%w[ant bear cat].any? { |word| word.length >= 4 } #=> true
[nil, true, 99].any? #=> true
any? is one of a number of tests that can be applied to an array to determine if there are none?, any?, one?, or all?.
ary.one?{ |e| e == 1 } # => true
ary.none?{ |e| e == 2 } # => true
ary.all? { |e| e.nil? } # => false
Your code fails because you're trying to use a non-existing any? method for a nil value, hence the error you got: "NoMethodError: undefined method `any?' for nil:NilClass"
ary[0] # => nil
ary.first # => nil
ary.first.respond_to?(:'any?') # => false
You have to pay attention to what you're doing. ary[0] or array.first returns the element at that array index, not an array.
empty? only checks to see if the container has elements in it. In other words, does it have a size > 0?
ary.empty? # => false
ary.size == 0 # => false
ary.size > 0 # => true
[].empty? # => true
[].size == 0 # => true
[].size > 0 # => false
1 Comment
Alex Strizhak
Thanks!
args.any?(&:nil?) look better for me.If you want to check if the array includes nil:
[nil, 1, 2].include?(nil) #=> true
answered Jun 23, 2014 at 23:35
Jorge de los Santos
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1 Comment
codenoob
Sometimes the best approach is the simplest approach, as EVERYONE will get the intent immediately when they look at the code. Particularly if it's me coming back to it. I don't want another "Why does that work again?" moment. Have enough already. This should be marked as the best answer.
any?'s default bahavior is to check for ant truthy value in the array.
# check if there are any truthy values in the array
[nil, nil, nil].any? #=> false
[nil, true, nil].any? #=> true
# check if all values are truthy
[true,Duck.new,2,'yes'].all? #=> true
[nil, false].all? #=> false
# check if none values are truthy
[nil,false,nil].none? #=> true
[Math::PI,nil,false].none? #=> false
All this methods accepts an optional block to customize the value beingchecked, which comes very handy in your specific use case:
[false, false, false].any?(&:nil?) => false
[false, false, nil].any?(&:nil?) => true
1 Comment
Cary Swoveland
Numbers is only concerned with
nil, not nil or false.array = [nil, nil, nil]
#=> [nil, nil, nil]
array[1].nil?
#=> true
Comments
You can turn nil values into booleans this way to check for them
array = [nil, nil, nil]
#=> [nil, nil, nil]
!array[1]
#=> true
!!array[1]
#=>false
However, using any? checks for the existence of something. You can use
array.any? {|item| !item }
#=> true
To check if there are any values that evaluate to false as a nil value does. Be careful if you might have a false value in your array though because it will also be evaluated as true using this this method.
Or you could just use:
array.any? { |item| item.nil? }
As other posters have suggested
Your problem is that you are calling the any? method on nil and not on an array.
2 Comments
Cary Swoveland
Numbers is only concerned with
nil, not nil or false.
onetwopunch
You're right, thats why I added the bit about nil as well :)
If you are checking that does the whole array contains nil than you can use any?
array = [nil, nil, nil]
#=> [nil, nil, nil]
array.any?
#=> false
false means that array does not contains any actual value.
OR do the comparison using uniq
array.uniq == [nil]
#=> true
