Ruby. How to know which class instance method is defined?

Question

I want to know which class method_missing is defined. It is defined in Object.

How can I figure out which class along the hierarchy overrides it?

Marek Lipka · Accepted Answer · 2014-11-25T08:29:29.090

6

You can use UnboundMethod#owner method to check where the method is implemented:

class A
  def method_missing(*args)
    # do something
  end
end
method = A.instance_method(:method_missing)
method.owner
# => A

Note: If the method is implemented in module (which is later mixed into the class hierarchy somewhere), owner will return this module.

edited Nov 25 '14 at 08:29

answered Nov 25 '14 at 08:24

Marek Lipka

Good answer. Correct me if I'm wrong, but I think you can stop with `method`, which returns `#` (assuming it's just for debugging and you don't need the class returned in the code itself). – Cary Swoveland Nov 25 '14 at 09:20
No, `A.method(:method_missing)` returns `Method` instance representing `BasicObject#method_missing`, instead of `A#method_missing`. It's because `A#method_missing` is implemented as instance method, not class method. – Marek Lipka Nov 25 '14 at 09:23
I was referring to the value of your variable `method`, which is displayed as `#`, showing the owner, `A`. Similarly, for `class B #`, again showing `A` as the owner. Correct? – Cary Swoveland Nov 25 '14 at 15:40
Yes, and it's exactly what OP wanted. – Marek Lipka Nov 25 '14 at 15:45
My only point was that you don't have to add `.owner` to see who the owner is. – Cary Swoveland Nov 25 '14 at 15:49
Oh, you're right. Though calling `owner` makes it clear, so I don't think my answer need modification. – Marek Lipka Nov 25 '14 at 17:40
@MarekLipka Yes, it helps. This is what I want. – Zhang Kai Yu Nov 26 '14 at 08:34
@CarySwoveland Both comments help. Thank you, too. – Zhang Kai Yu Nov 26 '14 at 08:36

1 Answers1