I have ruby array and it is nil but when I check using nil? and blank? it returns false
@a = [""]
@a.nil?
=> false
@a.empty?
=> false
How do I check for the nil condition that return true?
3 Answers
[""] is an array with a single element containing an empty String object. [].empty? will return true. @a.nil? is returning false because @a is an Array object, not nil.
Examples:
"".nil? # => false
[].nil? # => false
[""].empty? # => false
[].empty? # => true
[""].all? {|x| x.nil?} # => false
[].all? {|x| x.nil?} # => true
[].all? {|x| x.is_a? Float} # => true
# An even more Rubyish solution
[].all? &:nil? # => true
That last line demonstrates that [].all? will always return true, because if an Array is empty then by definition all of its elements (no elements) fulfill every condition.
Comments
p defined? "" #=> "expression"
p defined? nil #=> "nil"
The one "" you are thinking as nil, actually an expression. Look at the size of an empty array and non-empty array as below for more proof:
p [].size #=> 0
p [""].size #=> 1
Said the your #nil? and #empty gives false. Which is expected.
[""]is not nil. What are you trying to do?if @a == [""]?nil.