Class Module
In: lib/inactive_support/core_ext/module/aliasing.rb
Parent: Object


Public Instance methods

Allows you to make aliases for attributes, which includes getter, setter, and query methods.


  class Content < ActiveRecord::Base
    # has a title attribute

  class Email < Content
    alias_attribute :subject, :title

  e = Email.find(1)
  e.title    # => "Superstars"
  e.subject  # => "Superstars"
  e.subject? # => true
  e.subject = "Megastars"
  e.title    # => "Megastars"


# File lib/inactive_support/core_ext/module/aliasing.rb, line 63
  def alias_attribute(new_name, old_name)
    module_eval "def \#{new_name}; self.\#{old_name}; end\ndef \#{new_name}?; self.\#{old_name}?; end\ndef \#{new_name}=(v); self.\#{old_name} = v; end\n", __FILE__, __LINE__+1

Encapsulates the common pattern of:

  alias_method :foo_without_feature, :foo
  alias_method :foo, :foo_with_feature

With this, you simply do:

  alias_method_chain :foo, :feature

And both aliases are set up for you.

Query and bang methods (foo?, foo!) keep the same punctuation:

  alias_method_chain :foo?, :feature

is equivalent to

  alias_method :foo_without_feature?, :foo?
  alias_method :foo?, :foo_with_feature?

so you can safely chain foo, foo?, and foo! with the same feature.


# File lib/inactive_support/core_ext/module/aliasing.rb, line 23
  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, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}"
    alias_method without_method, target
    alias_method target, with_method
      when public_method_defined?(without_method)
        public target
      when protected_method_defined?(without_method)
        protected target
      when private_method_defined?(without_method)
        private target