rails--rails/actionpack/lib/action_controller/scaffolding.rb

module ActionController
  module Scaffolding # :nodoc:
    def self.append_features(base)
      super
      base.extend(ClassMethods)
    end

    # Scaffolding is a way to quickly put an Active Record class online by providing a series of standardized actions
    # for listing, showing, creating, updating, and destroying objects of the class. These standardized actions come
    # with both controller logic and default templates that through introspection already know which fields to display
    # and which input types to use. Example:
    #
    #  class WeblogController < ActionController::Base
    #    scaffold :entry
    #  end
    #
    # This tiny piece of code will add all of the following methods to the controller:
    #
    #  class WeblogController < ActionController::Base
    #    def index
    #      list
    #    end
    #
    #    def list
    #      @entries = Entry.find_all
    #      render_scaffold "list"
    #    end
    #  
    #    def show
    #      @entry = Entry.find(@params["id"])
    #      render_scaffold
    #    end
    #    
    #    def destroy
    #      Entry.find(@params["id"]).destroy
    #      redirect_to :action => "list"
    #    end
    #    
    #    def new
    #      @entry = Entry.new
    #      render_scaffold
    #    end
    #    
    #    def create
    #      @entry = Entry.new(@params["entry"])
    #      if @entry.save
    #        flash["notice"] = "Entry was successfully created"
    #        redirect_to :action => "list"
    #      else
    #        render_scaffold('new')
    #      end
    #    end
    #    
    #    def edit
    #      @entry = Entry.find(@params["id"])
    #      render_scaffold
    #    end
    #    
    #    def update
    #      @entry = Entry.find(@params["entry"]["id"])
    #      @entry.attributes = @params["entry"]
    #  
    #      if @entry.save
    #        flash["notice"] = "Entry was successfully updated"
    #        redirect_to :action => "show/" + @entry.id.to_s
    #      else
    #        render_scaffold('edit')
    #      end
    #    end
    #  end
    #
    # The <tt>render_scaffold</tt> method will first check to see if you've made your own template (like "weblog/show.rhtml" for 
    # the show action) and if not, then render the generic template for that action. This gives you the possibility of using the 
    # scaffold while you're building your specific application. Start out with a totally generic setup, then replace one template 
    # and one action at a time while relying on the rest of the scaffolded templates and actions.
    module ClassMethods
      # Adds a swath of generic CRUD actions to the controller. The +model_id+ is automatically converted into a class name unless
      # one is specifically provide through <tt>options[:class_name]</tt>. So <tt>scaffold :post</tt> would use Post as the class
      # and @post/@posts for the instance variables.
      # 
      # It's possible to use more than one scaffold in a single controller by specifying <tt>options[:suffix] = true</tt>. This will
      # make <tt>scaffold :post, :suffix => true</tt> use method names like list_post, show_post, and create_post 
      # instead of just list, show, and post. If suffix is used, then no index method is added.
      def scaffold(model_id, options = {})
        validate_options([ :class_name, :suffix ], options.keys)

        singular_name = model_id.id2name
        class_name    = options[:class_name] || Inflector.camelize(singular_name)
        plural_name   = Inflector.pluralize(singular_name)
        suffix        = options[:suffix] ? "_#{singular_name}" : ""

        unless options[:suffix]
          module_eval <<-"end_eval", __FILE__, __LINE__
            def index
              list
            end
          end_eval
        end
        
        module_eval <<-"end_eval", __FILE__, __LINE__
          def list#{suffix}
            @#{plural_name} = #{class_name}.find_all
            render#{suffix}_scaffold "list#{suffix}"
          end

          def show#{suffix}
            @#{singular_name} = #{class_name}.find(@params["id"])
            render#{suffix}_scaffold
          end
          
          def destroy#{suffix}
            #{class_name}.find(@params["id"]).destroy
            redirect_to :action => "list#{suffix}"
          end
          
          def new#{suffix}
            @#{singular_name} = #{class_name}.new
            render#{suffix}_scaffold
          end
          
          def create#{suffix}
            @#{singular_name} = #{class_name}.new(@params["#{singular_name}"])
            if @#{singular_name}.save
              flash["notice"] = "#{class_name} was successfully created"
              redirect_to :action => "list#{suffix}"
            else
              render#{suffix}_scaffold('new')
            end
          end
          
          def edit#{suffix}
            @#{singular_name} = #{class_name}.find(@params["id"])
            render#{suffix}_scaffold
          end
          
          def update#{suffix}
            @#{singular_name} = #{class_name}.find(@params["#{singular_name}"]["id"])
            @#{singular_name}.attributes = @params["#{singular_name}"]

            if @#{singular_name}.save
              flash["notice"] = "#{class_name} was successfully updated"
              redirect_to :action => "show#{suffix}", :id => @#{singular_name}.id.to_s
            else
              render#{suffix}_scaffold('edit')
            end
          end
          
          private
            def render#{suffix}_scaffold(action = caller_method_name(caller))
              if template_exists?("\#{self.class.controller_path}/\#{action}")
                render_action(action)
              else
                @scaffold_class = #{class_name}
                @scaffold_singular_name, @scaffold_plural_name = "#{singular_name}", "#{plural_name}"
                @scaffold_suffix = "#{suffix}"
                add_instance_variables_to_assigns

                @content_for_layout = @template.render_file(scaffold_path(action.sub(/#{suffix}$/, "")), false)
                self.active_layout ? render_file(self.active_layout, "200 OK", true) : render_file(scaffold_path("layout"))
              end
            end
            
            def scaffold_path(template_name)
              File.dirname(__FILE__) + "/templates/scaffolds/" + template_name + ".rhtml"
            end
            
            def caller_method_name(caller)
              caller.first.scan(/`(.*)'/).first.first # ' ruby-mode
            end
        end_eval
      end

      private
        # Raises an exception if an invalid option has been specified to prevent misspellings from slipping through 
        def validate_options(valid_option_keys, supplied_option_keys)
          unknown_option_keys = supplied_option_keys - valid_option_keys
          raise(ActionController::ActionControllerError, "Unknown options: #{unknown_option_keys}") unless unknown_option_keys.empty?
        end        
    end
  end
end