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"
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