From: nobu@...
Date: 2014-01-17T08:58:17+00:00
Subject: [ruby-core:59821] [ruby-trunk - Bug #9413] [Closed] Object Metaclass Constants Array doesn't Include Singleton Constant

Issue #9413 has been updated by Nobuyoshi Nakada.

Status changed from Open to Closed
% Done changed from 0 to 100

Applied in changeset r44628.

----------
eval.c: singleton class constants

* eval.c (rb_mod_s_constants): return its own constants for other
  than Module itself.  [ruby-core:59763] [Bug #9413]

----------------------------------------
Bug #9413: Object Metaclass Constants Array doesn't Include Singleton Constant
https://bugs.ruby-lang.org/issues/9413#change-44394

* Author: Dmitri Moore
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: core
* Target version: current: 2.2.0
* ruby -v: ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin12.0]
* Backport: 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED
----------------------------------------
Let's assume we have this Ruby class:

    class MyClass
      class << self
        MC_CONST = 30
      end
    end 

Then, let's instantiate `MyClass` and add another constant to the object's metaclass:

    m = MyClass.new
    class << m
      OBJ_MC_CONST = 50
    end

There are no issues with the object singleton constant:

    m.singleton_class::OBJ_MC_CONST # => 50 <-- [OK]
    m.singleton_class.constants.include? :OBJ_MC_CONST # => true <- [OK]

But not exactly what I'd expect with the class singleton constant: 

    MyClass.singleton_class::MC_CONST # => 30 <-- [OK]
    MyClass.singleton_class.const_get :MC_CONST # => 30 <-- [OK]
    MyClass.singleton_class.const_defined? :MC_CONST=> true <-- [OK]
    MyClass.singleton_class.constants.include? :MC_CONST # => false <-- [Why???]

Why does the array returned by `.constants` method on metaclass of `MyClass` class doesn't contain :MC_CONST?

Here is the SO (StackOverflow) thread for this http://stackoverflow.com/questions/21057002/where-are-the-ruby-class-singleton-constants-stored/21061117?iemail=1&noredirect=1#21061117



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