Can you override a method by including a module? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

Overriding method by another defined in module

Here's some code:

class Foo
  def bar
    puts "Original ba开发者_如何学JAVAr"
  end
end

module M
  def bar
    puts "Called M::bar"    
  end
end

Foo.send(:include,M)
Foo.new.bar
# => Original bar

Does ruby prevent overriding a previously defined method when a method of the same name is "included"?

---

I don't quite understand your question. What, exactly, do you think is "prevented" here, and by whom?

This is precisely how it is supposed to work. Module#include mixes in the module as the direct superclass of whatever class it is being mixed into. M is a superclass of Foo, so Foo#bar overrides M#bar, because that's how inheritance works: subclasses override superclasses, not the other way around. Nothing is being "prevented" here, of course you can still override Foo#bar in a subclass of Foo.

You can clearly see the ancestry:

class FooS; end
module M; end
class Foo < FooS; include M end

Foo.ancestors # => [Foo, M, FooS, Object, Kernel, BasicObject]

---

Rephrasing @Jorg's answer:

If you do

Foo.send(:include,M)
Foo.ancestors

You get back

[Foo, M, Object, Kernel, BasicObject]

That means that when bar gets called, it looks to see if there's Foo#bar first, and only if that didn't exist would it try looking at M#bar (and then Object, Kernel, BasicObject and then calls method_missing).

Personally speaking, I wouldn't mind the ability for M to be looked at first, before looking at Foo. I've heard there's talk of adding to Ruby 2.0 the ability to do this, but that's not going to help you right now.

---

Your include call doesn't do what you think... try Foo.send(:extend,M)