From: Joshua Ballanco <jballanc@...>
Date: 2012-03-18T10:20:22+09:00
Subject: [ruby-core:43379] [ruby-trunk - Bug #5544] Lookup scope for class variables in class_eval'd procs changed in 1.9.3


Issue #5544 has been updated by Joshua Ballanco.


I suppose so long as it is documented, the difference is ok. I think this can be closed in that case.
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Bug #5544: Lookup scope for class variables in class_eval'd procs changed in 1.9.3
https://bugs.ruby-lang.org/issues/5544#change-24684

Author: Joshua Ballanco
Status: Closed
Priority: Normal
Assignee: Shugo Maeda
Category: core
Target version: 
ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]


When using class_eval with a proc, references to class variables scoped to the receiver in 1.9.2, but in 1.9.3 class variables are now lexically scoped to the environment of the proc. For example, this code:

    class Foo
      def initialize
        @@value = "Set from Foo initialize"
      end
      def report
        @@value
      end
    end
    
    class Bar
      def initialize
        @@value = "Set from Bar initialize"
      end
      def report
        @@value
      end
      def monkey
        Foo.class_eval do
          def set(value)
            @@value = value
          end
        end
      end
    end
    
    b = Bar.new
    b.monkey
    f = Foo.new
    
    puts "Before monkeying:"
    puts "Bar's class var: #{b.report}"
    puts "Foo's class var: #{f.report}"
    
    f.set("Set through Monkey")
    
    puts "After monkeying:"
    puts "Bar's class var: #{b.report}"
    puts "Foo's class var: #{f.report}"

Running under 1.9.2-p290:

    Before monkeying:
    Bar's class var: Set from Bar initialize
    Foo's class var: Set from Foo initialize
    After monkeying:
    Bar's class var: Set from Bar initialize
    Foo's class var: Set through Monkey

Running under 1.9.3-p0:

    Before monkeying:
    Bar's class var: Set from Bar initialize
    Foo's class var: Set from Foo initialize
    After monkeying:
    Bar's class var: Set through Monkey
    Foo's class var: Set from Foo initialize




-- 
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