Checkout of Instiki Trunk 1/21/2007.

vendor/rails/actionpack/lib/action_controller/dependencies.rb

@@ -0,0 +1,83 @@
+module ActionController #:nodoc:
+  module Dependencies #:nodoc:
+    def self.append_features(base)
+      super
+      base.extend(ClassMethods)
+    end
+
+    # Dependencies control what classes are needed for the controller to run its course. This is an alternative to doing explicit
+    # +require+ statements that bring a number of benefits. It's more succinct, communicates what type of dependency we're talking about,
+    # can trigger special behavior (as in the case of +observer+), and enables Rails to be clever about reloading in cached environments
+    # like FCGI. Example:
+    #
+    #   class ApplicationController < ActionController::Base
+    #     model    :account, :company, :person, :project, :category
+    #     helper   :access_control
+    #     service  :notifications, :billings
+    #     observer :project_change_observer
+    #   end
+    #
+    # Please note that a controller like ApplicationController will automatically attempt to require_dependency on a model of its 
+    # singuralized name and a helper of its name. If nothing is found, no error is raised. This is especially useful for concrete 
+    # controllers like PostController:
+    #
+    #   class PostController < ApplicationController
+    #     # model  :post (already required)
+    #     # helper :post (already required)
+    #   end
+    #
+    # Also note, that if the models follow the pattern of just 1 class per file in the form of MyClass => my_class.rb, then these
+    # classes don't have to be required as Active Support will auto-require them.
+    module ClassMethods #:nodoc:
+      # Specifies a variable number of models that this controller depends on. Models are normally Active Record classes or a similar
+      # backend for modelling entity classes.
+      def model(*models)
+        require_dependencies(:model, models)
+        depend_on(:model, models)
+      end
+
+      # Specifies a variable number of services that this controller depends on. Services are normally singletons or factories, like
+      # Action Mailer service or a Payment Gateway service.
+      def service(*services)
+        require_dependencies(:service, services)
+        depend_on(:service, services)
+      end
+      
+      # Specifies a variable number of observers that are to govern when this controller is handling actions. The observers will
+      # automatically have .instance called on them to make them active on assignment.
+      def observer(*observers)
+        require_dependencies(:observer, observers)
+        depend_on(:observer, observers)
+        instantiate_observers(observers)
+      end
+
+      # Returns an array of symbols that specify the dependencies on a given layer. For the example at the top, calling
+      # <tt>ApplicationController.dependencies_on(:model)</tt> would return <tt>[:account, :company, :person, :project, :category]</tt>
+      def dependencies_on(layer)
+        read_inheritable_attribute("#{layer}_dependencies")
+      end
+    
+      def depend_on(layer, dependencies) #:nodoc:
+        write_inheritable_array("#{layer}_dependencies", dependencies)
+      end
+
+      private
+        def instantiate_observers(observers)
+          observers.flatten.each { |observer| Object.const_get(Inflector.classify(observer.to_s)).instance }
+        end
+        
+        def require_dependencies(layer, dependencies)
+          dependencies.flatten.each do |dependency|
+            begin
+              require_dependency(dependency.to_s)
+            rescue LoadError => e
+              raise LoadError.new("Missing #{layer} #{dependency}.rb").copy_blame!(e)
+            rescue Object => exception
+              exception.blame_file! "=> #{layer} #{dependency}.rb"
+              raise
+            end
+          end
+        end
+    end
+  end
+end