From: Daniel DeLorme <dan-ml@...42.com>
Date: 2008-12-13T14:25:50+09:00
Subject: singleton methods vs. meta instance methods

If I understand the ruby object model correctly, then an object's 
singleton methods are defined as the instance methods of that object's 
meta/singleton class. So I tried to confirm this:

obj = Object.new
obj_meta = (class << obj;self;end)
def obj.foobar; end
obj.singleton_methods            #=> ["foobar"]
obj_meta.instance_methods(false) #=> ["foobar"]

So far so good. But if I try the same thing with a class:

class A; end
A_meta = (class << A;self;end)
def A.foobar; end
A.singleton_methods            #=> ["foobar"]
A_meta.instance_methods(false) #=> ["allocate", "superclass", "foobar", 
"new"]

I understand why those 3 extra methods appear, but in that case 
shouldn't they also appear as part of A.singleton_methods? Furthermore 
this does not happen with builtin classes. Does anyone have an 
explanation for what is going on here?

Daniel