Module: ActiveSupport::Deprecation::DeprecatedConstantAccessor

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Included In: `::AbstractController::Helpers`, `::ActionController::Base`, `::ActionController::ContentSecurityPolicy`, `::ActionController::Helpers`, `::ActionController::RequestForgeryProtection`, `::ActionDispatch`, `::ActionMailer::Base`, `::ActionView::FileSystemResolver`, `::ActionView::FixtureResolver`, `::ActionView::NullResolver`, `::ActionView::Resolver`, `::ActionView::TestCase`, `::ActionView::TestCase::Behavior`, `::ActionView::TestCase::TestController`, `::ActiveRecord`, Rails::ApplicationController, `::Rails::Generators::Testing`, `::Rails::HealthController`, Rails::InfoController, Rails::MailersController, Rails::WelcomeController
Defined in:	activesupport/lib/active_support/deprecation/constant_accessor.rb

Overview

DeprecatedConstantAccessor transforms a constant into a deprecated one by hooking const_missing.

It takes the names of an old (deprecated) constant and of a new constant (both in string form) and a deprecator.

The deprecated constant now returns the same object as the new one rather than a proxy object, so it can be used transparently in rescue blocks etc.

PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)

# (In a later update, the original implementation of {PLANETS} has been removed.)

PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
include ActiveSupport::Deprecation::DeprecatedConstantAccessor
deprecate_constant 'PLANETS', 'PLANETS_POST_2006', deprecator: ActiveSupport::Deprecation.new

PLANETS.map { |planet| planet.capitalize }
# => DEPRECATION WARNING: PLANETS is deprecated! Use PLANETS_POST_2006 instead.
     (Backtrace information…)
     ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]

Class Method Summary

.included(base)

Class Method Details

.included(base)

[ GitHub ]

# File 'activesupport/lib/active_support/deprecation/constant_accessor.rb', line 28


def self.included(base)
  require "active_support/inflector/methods"

  extension = Module.new do
    def const_missing(missing_const_name)
      if class_variable_defined?(:@@_deprecated_constants)
        if (replacement = class_variable_get(:@@_deprecated_constants)[missing_const_name.to_s])
          replacement[:deprecator].warn(replacement[:message] || "#{name}::#{missing_const_name} is deprecated! Use #{replacement[:new]} instead.", caller_locations)
          return ActiveSupport::Inflector.constantize(replacement[:new].to_s)
        end
      end
      super
    end

    def deprecate_constant(const_name, new_constant, message: nil, deprecator: nil)
      ActiveSupport.deprecator.warn("DeprecatedConstantAccessor.deprecate_constant without a deprecator is deprecated") unless deprecator
      deprecator ||= ActiveSupport::Deprecation._instance
      class_variable_set(:@@_deprecated_constants, {}) unless class_variable_defined?(:@@_deprecated_constants)
      class_variable_get(:@@_deprecated_constants)[const_name.to_s] = { new: new_constant, message: message, deprecator: deprecator }
    end
  end
  base.singleton_class.prepend extension
end