Module which provides the ability to unscope associations

unscoped_associations.rb

# Provides the ability to unscope associations, this solves problems described in
# http://stackoverflow.com/questions/1540645/how-to-disable-default-scope-for-a-belongs-to/11012633#11012633
#
# Examples
#
#    class Document < ActiveRecord::Base
#      default_scope where(deleted: false)
#    end
#
#    class Comment < ActiveRecord::Base
#      extend Unscoped
#
#      belongs_to :document
#      unscope :document
#    end
#
module UnscopedAssociations

  # Public: Ensure a previously defined association is not scoped by a default_scope.
  #
  # associations - The Symbol with the name(s) of the associations to unscope.
  #
  # Examples
  #
  #    # Unscope a single association
  #    unscope :document
  #
  #    # Unscope multiple in one way.
  #    unscope :document, :comments
  #
  # Raises ArgumentError if the named association does not exist on the model, so ensure
  # the association is defined _before_ calling `unscope`.
  #
  # Returns nothing.
  def unscope(*associations)
    associations.flatten.each do |association|
      unless self.reflect_on_association(*association)
        raise ArgumentError, "no association named #{association} exists on this model"
      end
      
      class_eval <<-RUBY, __FILE__, __LINE__ + 1
        if self.reflect_on_association(#{association.inspect}).options[:polymorphic]
          # for polymorphic association the klass is not known for association reflection
          def #{association}(force_reload = false)
            self.association(#{association.inspect}).klass.unscoped { super(force_reload) }
          end
        else
          def #{association}(force_reload = false)
            self.class.reflect_on_association(#{association.inspect}).klass.unscoped { super(force_reload) }
          end
        end
      RUBY
    end
  end

  # Public: Define an association of the given type and ensure it is not scoped by default_scope.
  def unscoped_association(association_method, association, *args)
    send(association_method, association, *args)
    unscope(association)
  end

  # Public: Define a belongs_to association that ignores the target class's default_scope.
  def belongs_to_unscoped(*args)
    unscoped_association(:belongs_to, *args)
  end

  # Public: Define a has_one association that ignores the target class's default_scope.
  def has_one_unscoped(*args)
    unscoped_association(:has_one, *args)
  end

  # Public: Define a has_many association that ignores the target class's default_scope.
  def has_many_unscoped(*args)
    unscoped_association(:has_many, *args)
  end
end