Can Ruby return nothing?

Question

Can I return nothing in ruby?

Just for educational purpose

For example:

myarray = [1,2,3]
myarray << some_method

def some_method
         


        

Answer 1

Nothing does not mean anything to ruby from what i know :) You can define your own nothing though and throw it as much as possible. In ruby, if you do not explicitly return something, the last evaluated expression is returned.

Answer 2

You can't return "nothing" from a method in ruby. As you point out you could conditionally add elements to your array. You can also invoke .compact on your array to remove all nil elements.

Answer 3

You can simulate Nothing with exceptions.

class NothingError < RuntimeError  
end  

def nothing
  raise NothingError
end

def foo x
  if x>0 then x else nothing end
end

def nothingness
  begin
    yield
  rescue NothingError
  end
end

a = [1,2,3]
nothingness { a << foo(4) }
nothingness { a << foo(0) }

Probably not a great idea however ...

Answer 4

You can't return a real Nothing with Ruby. Everything is a object. But you can create a fake Nothing to do it. See:

Nothing = Module.new # Same as module Nothing; end
class Array
  alias old_op_append <<
  def <<(other)
    if other == Nothing
      self
    else
      old_op_append(other)
    end
  end
end

This is ugly but works in your sample. (Nothing keeps being a object.)

Answer 5

Basically, what you are looking for is a statement. But Ruby doesn't have statements, only expressions. Everything is an expression, i.e. everything returns a value.

Answer 6

No, you can't return nothing. In ruby you always return something (even if it's just nil) - no way around that.