resource_controller.rb

class ResourceController < Application
  @@page_size = nil
  
  def index
    display_collection
  end

  def show
    display get_resource
  end

  def new
    only_provides :html
    display new_resource
  end

  def edit
    only_provides :html
    display get_resource
  end

  def create
    if new_resource.save
      redirect resource(@resource), :message => {:notice => "#{resource_class_name} was successfully created"}
    else
      raise NotAcceptable
    end
  end

  def update
    if get_resource.update_attributes(get_attributes)
      redirect resource(@resource)
    else
      raise NotAcceptable
    end
  end

  def destroy
    if get_resource.destroy
      redirect resource(controller_name.to_sym)
    else
      raise InternalServerError
    end
  end

  def delete(id)
    destroy(id)
  end

  class <<self
    def paginate(page_size = 25)
      @@page_size = page_size
    end
  end

  protected
  def get_resource
    params.each do |k, v|
      case k.to_s
      when /(.+)_id/
        raise "Resources more than one level deep not supported" if @parent
        @parent = find_resource($1.camel_case, v)
      when 'id'
        @resource = find_resource(resource_class_name, v)
      end
    end

    @resource
  end

  def get_collection
    name = controller_name.snake_case

    @collection = if @parent
                    @parent.send(name.to_sym)
                  else
                    resource_class.all
                  end

    if @@page_size
      @collection = @collection.paginate(:page => params[:page], :per_page => @@page_size)
    end

    instance_variable_set(:"@#{name}", @collection)
  end

  def get_attributes
    params[resource_class_name.snake_case.to_sym] || {}
  end

  def new_resource
    @resource = resource_class.new(get_attributes)
    instance_variable_set(:"@#{resource_class_name.snake_case}", @resource)
  end

  def display_collection
    display get_collection
  end

  private
  def find_resource(class_name, id)
    resource = Kernel.const_get(class_name).get!(id)
    instance_variable_set(:"@#{class_name.snake_case}", resource)
  end

  def resource_class_name
    controller_name.singular.camel_case
  end

  def resource_class
    Kernel.const_get(resource_class_name)
  end
end