Chaining block passing in ruby [duplicate]

Question

This question already has answers here:

Chaining methods using Symbol#to_proc shorthand in Ruby? (4 answers)

Closed 9 years ago.

lets say I have an array

array = [[2], [1], [0]]

I can do this:

array.map(&:any?)
# => [true, true, true]

and I can do this:

array.map do |x|
    x.any?(&:zero?)
end
# => [false, false, true]

why cant i do this? (or something similar):

array.map(&:any?(&:zero?))

returns SyntaxError: unexpected '(', expecting ')'

array.map(&:any?(&:zero?))

Thank you for your time.

Answer 1

Because :any?(&:zero?) is not an appropriate symbol literal. You can make it a symbol by doing :"any?(&:zero?)", but still, there is no such method.

Answer 2

Reasons why are explained in other answers. You can however use the shortcut for anything if you define a proc:

any_zeros= ->(o) { o.any?(&:zero?) }
array = [[2], [1], [0]].map(&any_zeros)

Answer 3

Why? Simple answer: because Ruby doesn't include syntax for it.

You are basically trying to pass a default argument to the method. The Ruby devs, at some point, made a decision that a feature like this was too much work and extra complication for what can be achieved using this little code:

array.map {|e| x.any?(&:zero?)}