instance method cattr_writer

# File activesupport/lib/active_support/core_ext/class/attribute_accessors.rb, line 29
  def cattr_writer(*syms)
    options = syms.extract_options!
    syms.flatten.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
        " unless options[:instance_writer] == false }
      EOS
    end
  end