rails / activesupport / lib / active_support / core_ext / module / aliasing.rb

aliasing.rb

class Module
  def alias_method_chain(target, feature)
    # Strip out punctuation on predicates or bang methods since
    # e.g. target?_without_feature is not a valid method name.
    aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1
    yield(aliased_target, punctuation) if block_given?

    with_method = "#{aliased_target}_with_#{feature}#{punctuation}"
    without_method = "#{aliased_target}_without_#{feature}#{punctuation}"

    alias_method without_method, target
    alias_method target, with_method

    share_access_modifier target, without_method
  end

  def share_access_modifier(new_method, old_method)
    modifier = access_modifier(old_method)
    modifier and __send__(modifier, new_method)
  end

  def access_modifier(method_name)
    case
    when public_method_defined?(method_name)
      :public
    when protected_method_defined?(method_name)
      :protected
    when private_method_defined?(method_name)
      :private
    end
  end

  def alias_attribute(new_name, old_name)
    module_eval <<-STR, __FILE__, __LINE__ + 1
      def #{new_name}; self.#{old_name}; end          # def subject; self.title; end
      share_access_modifier(#{new_name}, #{old_name})
    STR

    respond_to?("#{old_name}?") and module_eval <<-STR, __FILE__, __LINE__ + 1
      def #{new_name}?; self.#{old_name}?; end        # def subject?; self.title?; end
      share_access_modifier(#{new_name}?, #{old_name}?)
    STR

    respond_to?("#{old_name}=") and module_eval <<-STR, __FILE__, __LINE__ + 1
      def #{new_name}=(v); self.#{old_name} = v; end  # def subject=(v); self.title = v; end
      share_access_modifier(#{new_name}=, #{old_name}=)
    STR
  end
end