activesupport/lib/active_support/module_attribute_accessors.rb


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# Extends the module object with module and instance accessors for class attributes, 
# just like the native attr* accessors for instance attributes.
class Module # :nodoc:
  def mattr_reader(*syms)
    syms.each do |sym|
      class_eval(<<-EOS, __FILE__, __LINE__)
        unless defined? @@#{sym}
          @@#{sym} = nil
        end
        
        def self.#{sym}
          @@#{sym}
        end

        def #{sym}
          @@#{sym}
        end
      EOS
    end
  end
  
  def mattr_writer(*syms)
    syms.each do |sym|
      class_eval(<<-EOS, __FILE__, __LINE__)
        unless defined? @@#{sym}
          @@#{sym} = nil
        end
        
        def self.#{sym}=(obj)
          @@#{sym} = obj
        end

        def #{sym}=(obj)
          @@#{sym} = obj
        end
      EOS
    end
  end
  
  def mattr_accessor(*syms)
    mattr_reader(*syms)
    mattr_writer(*syms)
  end
end