module Authority # Should be included into all models in a Rails app. Provides the model # with both class and instance methods like `updatable_by?(user)` # Exactly which methods get defined is determined from `config.abilities`; # the module is evaluated after any user-supplied config block is run # in order to make that possible. # All delegate to the methods of the same name on the model's authorizer. module Abilities extend ActiveSupport::Concern # Assume authorizer is `ApplicationAuthorizer` (but let the user change that) included do class_attribute :authorizer_name self.authorizer_name = "ApplicationAuthorizer" end module ClassMethods Authority.adjectives.each do |adjective| class_eval <<-RUBY, __FILE__, __LINE__ + 1 def #{adjective}_by?(user, options = {}) if options.empty? authorizer.#{adjective}_by?(user) else authorizer.#{adjective}_by?(user, options) end end RUBY end # @return [Class] of the designated authorizer def authorizer @authorizer ||= authorizer_name.constantize # Get an actual reference to the authorizer class rescue NameError raise Authority::NoAuthorizerError.new("#{authorizer_name} does not exist in your application") end end Authority.adjectives.each do |adjective| class_eval <<-RUBY, __FILE__, __LINE__ + 1 def #{adjective}_by?(user, options = {}) if options.empty? authorizer.#{adjective}_by?(user) else authorizer.#{adjective}_by?(user, options) end end def authorizer self.class.authorizer.new(self) # instantiate on every check, in case model has changed end RUBY end end end