Ruby send vs __send__

Question

I understand the concept of some_instance.send but I\'m trying to figure out why you can call this both ways. The Ruby Koans imply that there is some reason bey

Answer 1

If you really need send to behave like it would normally do, you should use __send__, because it won't (it shouldn't) be overriden. Using __send__ is especially useful in metaprogramming, when you don't know what methods the class being manipulated defines. It could have overriden send.

Watch:

class Foo
  def bar?
    true
  end

  def send(*args)
    false
  end
end

foo = Foo.new
foo.send(:bar?)
# => false
foo.__send__(:bar?)
# => true

If you override __send__, Ruby will emit a warning:

warning: redefining `__send__' may cause serious problems

Some cases where it would be useful to override send would be where that name is appropriate, like message passing, socket classes, etc.