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Inherited Resources

Version: 0.9.0 / License: MIT

Description

Inherited Resources speeds up development by making your controllers inherit
all restful actions so you just have to focus on what is important. It makes
your controllers more powerful and cleaner at the same time.

Plus, making your controllers follow a pattern, it helps you to write better
code by following fat models and skinny controllers convention.

Inherited Resources is tested and compatible with Rails 2.2.x and Rails 2.3.×.

keywords: resources, controller, singleton, belongs_to, polymorphic, named_scope and I18n

Installation

Install Inherited Resources is very easy. It is stored in GitHub, so just run
the following:

gem sources -a http://gems.github.com sudo gem install josevalim-inherited_resources

If you want it as plugin, just do:

script/plugin install git://github.com/josevalim/inherited_resources.git

Basic Usage

To use Inherited Resources you just have to inherit (duh) it:

   class ProjectsController < InheritedResources::Base
   end

And all actions are defined and working, check it! Your projects collection
(in the index action) is still available in the instance variable @projects
and your project resource (all other actions) is available as @ project.

The next step is to define which mime types this controller provides:

   class ProjectsController < InheritedResources::Base
     respond_to :html, :xml, :json
   end

You can also specify them based per action:

   class ProjectsController < InheritedResources::Base
     respond_to :html, :xml, :json
     respond_to :js, :only => :create
     respond_to :iphone, :except => [ :edit, :update ]
   end

For each request, it first checkes if the “controller/action.format” file is
available (for example “projects/create.xml”) and if it’s not, it checks if
the resource respond to :to_format (in this case, :to_xml). Otherwise returns 404.

Another option is to specify which actions the controller will inherit from
the InheritedResources::Base:

   class ProjectsController < InheritedResources::Base
     actions :index, :show, :new, :create
   end

Or:

   class ProjectsController < InheritedResources::Base
     actions :all, :except => [ :edit, :update, :destroy ]
   end

In your views, you will get the following helpers:

   resource        #=> @project
   collection      #=> @projects
   resource_class  #=> Project

As you might expect, collection (@projects instance variable) is only available
on index actions.

If for some reason you cannot inherit from InheritedResources::Base, you can
call inherit_resources or resource_controller in your controller class scope:

  class AccountsController < ApplicationController
    inherit_resources # or resource_controller
  end

Overwriting defaults

Whenever you inherit from InheritedResources, several defaults are assumed.
For example you can have an AccountsController to account management while the
resource is an User:

   class AccountsController < InheritedResources::Base
     defaults :resource_class => User, :collection_name => 'users', :instance_name => 'user'
   end

In the case above, in your views you will have @users and @user variables, but
the routes used will still be accounts_url and account_url. If you plan also to
change the routes, you can use :route_collection_name and :route_instance_name.

Namespaced controllers work out of the box, but if you need to specify a
different route prefix, you can do the following:

   class Administrators::PeopleController < InheritedResources::Base
     defaults :route_prefix => 'admin'
   end

Then your named routes will be: ‘admin_people_url’, ‘admin_person_url’ instead
of ‘administrators_people_url’ and ‘administrators_person_url’.

If you want to customize how resources are retrieved you can overwrite
collection and resource methods. The first is called on index action and the
second on all other actions. Let’s suppose you want to add pagination to your
projects collection:

   class ProjectsController < InheritedResources::Base
     protected
       def collection
         @projects ||= end_of_association_chain.paginate(params[:page]).all
       end
   end

The end_of_association_chain returns your resource after nesting all associations
and scopes (more about this below).

InheritedResources also introduces another method called begin_of_association_chain.
It’s mostly used when you want to create resources based on the @current_user and
you have urls like “account/projects”. In such cases, you have to do
@current_user.projects.find or @current_user.projects.build in your actions.

You can deal with it just doing:

   class ProjectsController < InheritedResources::Base
     protected
       def begin_of_association_chain
         @current_user
       end
   end

Overwriting actions

Let’s suppose that after destroying a project you want to redirect to your
root url instead of redirecting to projects url. You just have to do:

   class ProjectsController < InheritedResources::Base
     def destroy
       super do |format|
         format.html { redirect_to root_url }
       end
     end
   end

You are opening your action and giving the parent action a new behavior. No
tricks, no DSL, just Ruby.

On the other hand, I have to agree that calling super is not very readable.
That’s why all methods have aliases. So this is equivalent:

   class ProjectsController < InheritedResources::Base
     def destroy
       destroy! do |format|
         format.html { redirect_to root_url }
       end
     end
   end

Even more, since most of the times when you change a create, update or destroy
action is because you want to to change to where it redirects, a shortcut is
provided. So you can do:

   class ProjectsController < InheritedResources::Base
     def destroy
       destroy!{ root_url }
     end
   end

Now let’s suppose that before create a project you have to do something special
but you don’t want to create a before filter for it:

   class ProjectsController < InheritedResources::Base
     def create
       @project = Project.new(params[:project])
       @project.something_special!
       create!
     end
   end

Yes, that simple! The nice part is since you already set the instance variable
@project, it will not build a project again.

Before we finish this topic, we should talk about one more thing: “success/failure
blocks”. Let’s suppose that when we update our project, in case of failure, we
want to redirect to the project url instead of re-rendering the edit template.

Our first attempt to do this would be:

   class ProjectsController < InheritedResources::Base
     def update
       update! do |format|
         unless @project.errors.empty? # failure
           format.html { redirect_to project_url(@project) }
         end
       end
     end
   end

Looks to verbose, right? We can actually do:

   class ProjectsController < InheritedResources::Base
     def update
       update! do |success, failure|
         failure.html { redirect_to project_url(@project) }
       end
     end
   end

Much better! So explaining everything: when you give a block which expects one
argument it will be executed in both scenarios: success and failure. But If you
give a block that expects two arguments, the first will be executed only in
success scenarios and the second in failure scenarios. You keep everything
clean and organized inside the same action.

Some DSL

For those DSL lovers, InheritedResources won’t leave you alone. You can overwrite
your success/failure blocks straight from your class binding. For it, you just
need to add a DSL block to your application controller:

    class ApplicationController < ActionController::Base
      include InheritedResources::DSL
    end

And then you can rewrite the last example as:

    class ProjectsController < InheritedResources::Base
      update! do |success, failure|
        failure.html { redirect_to project_url(@project) }
      end
    end

Flash messages and I18n

Flash messages are powered by I18n api. It checks for messages in the following
order:

   flash.controller_name.action_name.status
   flash.actions.action_name.status

If none is available, a default message in english set. In a create action
on projects controller, it will search for:

   flash.projects.create.status
   flash.actions.create.status

The status can be :notice (when the object can be created, updated
or destroyed with success) or :error (when the objecy cannot be created
or updated).

Those messages are interpolated by using the resource class human name, which
is also localized and it means you can set:

   flash:
     actions:
       create:
         notice: "Hooray! {{resource_name}} was successfully created!"

It will replace {{resource_name}} by the human name of the resource class,
which is “Project” in this case.

But sometimes, flash messages are not that simple. Sometimes you want to say
the title of the project while updating a project. Well, that’s easy also:

   flash:
     projects:
       update:
         notice: "Hooray! The project "{{project_title}}" was updated!"

Since :project_title is not available for interpolation by default, you have
to overwrite interpolation_options.

   def interpolation_options
     { :project_title => @project.title }
   end

Then you will finally have:

“Hooray! The project “Plataforma” was updated!"

By default, resource name is capitalized. If you want to make it lower case, you
can add to your application controller:

   def interpolation_options
     { :resource_name => resource_class.human_name.downcase }
  end

Finally, if your controller is namespaced, for example Admin::ProjectsController,
the messages will be checked in the following order:

   flash.admin.projects.create.notice
   flash.admin.actions.create.notice
   flash.projects.create.notice
   flash.actions.create.notice

Has Scope

InheritedResources tries to integrate nicely with your model. In order to do so,
it also is named_scope fluent. Let’s suppose our Project model with the scopes:

  class Project < ActiveRecord::Base
    named_scope :featured, :conditions => { :featured => true }
    named_scope :by_methodology, proc {|methodology| { :conditions => { :methodology => methodology } } }
    named_scope :limit, proc{|limit| :limit => limit.to_i }
  end

Your controller:

  class ProjectsController < InheritedResources::Base
    has_scope :featured, :boolean => true, :only => :index
    has_scope :by_methodology
    has_scope :limit, :default => 10
  end

Then for each request:

/projects  # acts like a normal request, but returning 10 projects
/projects?featured=true  # calls the featured named scope and bring 10 featured projects
/projects?featured=true&by_methodology=agile&limit=20  # brings 20 featured projects with methodology agile

You can retrieve the current scopes in use with :current_scopes method.
In the last case, it would return:

  { :featured => "true", :by_methodology => "agile", :limit => "20" }

Finally, let’s suppose you store on the session how many projects the user sees
per page. In such cases, you can give a proc as default value:

   has_scope :limit, :default => proc{|c| c.session[:limit] || 10 }

Belongs to

Finally, our Projects are going to get some Tasks. Then you create a
TasksController and do:

   class TasksController < InheritedResources::Base
     belongs_to :project
   end

belongs_to accepts several options to be able to configure the association.
For example, if you want urls like /projects/:project_title/tasks, you can
customize how InheritedResources find your projects:

   class TasksController < InheritedResources::Base
     belongs_to :project, :finder => :find_by_title!, :param => :project_title
   end

It also accepts :route_name, :parent_class and :instance_name as options.
Check the lib/inherited_resources/class_methods.rb for more.

Nested belongs to

Now, our Tasks get some Comments and you need to nest even deeper. Good
practices says that you should never nest more than two resources, but sometimes
you have to for security reasons. So this is an example of how you can do it:

   class CommentsController < InheritedResources::Base
     nested_belongs_to :project, :task
   end

If you need to configure any of these belongs to, you can nest them using blocks:

   class CommentsController < InheritedResources::Base
     belongs_to :project, :finder => :find_by_title!, :param => :project_title do
       belongs_to :task
     end
   end

Warning: calling several belongs_to is the same as nesting them:

   class CommentsConroller < InheritedResources::Base
     belongs_to :project
     belongs_to :task
   end

In other words, the code above is the same as calling nested_belongs_to.

Polymorphic belongs to

We can go even further. Let’s suppose our Projects can now have Files, Messages
and Tasks, and they are all commentable. In this case, the best solution is to
use polymorphism:

   class CommentsController < InheritedResources::Base
     belongs_to :task, :file, :message, :polymorphic => true # polymorphic_belongs_to :task, :file, :message
   end

You can even use it with nested resources:

   class CommentsController < InheritedResources::Base
     belongs_to :project do
       belongs_to :task, :file, :message, :polymorphic => true
     end
   end

The url in such cases can be: /project/1/task/13/comments /project/1/file/11/comments /project/1/message/9/comments

When using polymorphic associations, you get some free helpers:

   parent?         #=> true
   parent_type     #=> :task
   parent_class    #=> Task
   parent          #=> @task

Optional belongs to

Later you decide to create a view to show all comments, independent if they belong
to a task, file or message. You can reuse your polymorphic controller just doing:

  class ProjectsController < InheritedResources::Base
    belongs_to :task, :file, :message, :optional => true # optional_belongs_to :task, :file, :message
  end

This will handle all those urls properly: /comment/1 /tasks/2/comment/5 /files/10/comment/3 /messages/13/comment/11

This is treated as a special type of polymorphic associations, thus all helpers
are available. As you expect, when no parent is found, the helpers return:

   parent?         #=> false
   parent_type     #=> nil
   parent_class    #=> nil
   parent          #=> nil

Singletons

Now we are going to add manager to projects. We say that Manager is a singleton
resource because a Project has just one manager. You should declare it as
has_one (or resource) in your routes.

To declare an association as singleton, you just have to give the :singleton
option.

   class ManagersController < InheritedResources::Base
     belongs_to :project, :singleton => true   # singleton_belongs_to :project
   end

It will deal with everything again and hide the action :index from you.

URL Helpers

When you use InheritedResources it creates some URL helpers.
And they handle everything for you. :)

   # /posts/1/comments
   resource_url               # => /posts/1/comments/#{@comment.to_param}
   resource_url(comment)      # => /posts/1/comments/#{comment.to_param}
   new_resource_url           # => /posts/1/comments/new
   edit_resource_url          # => /posts/1/comments/#{@comment.to_param}/edit
   edit_resource_url(comment) #=>  /posts/1/comments/#{comment.to_param}/edit
   collection_url             # => /posts/1/comments

   # /projects/1/tasks
   resource_url               # => /projects/1/tasks/#{@task.to_param}
   resource_url(task)         # => /projects/1/tasks/#{task.to_param}
   new_resource_url           # => /projects/1/tasks/new
   edit_resource_url          # => /projects/1/tasks/#{@task.to_param}/edit
   edit_resource_url(task)    # => /projects/1/tasks/#{task.to_param}/edit
   collection_url             # => /projects/1/tasks

   # /users
   resource_url               # => /users/#{@user.to_param}
   resource_url(user)         # => /users/#{user.to_param}
   new_resource_url           # => /users/new
   edit_resource_url          # => /users/#{@user.to_param}/edit
   edit_resource_url(user)    # => /users/#{user.to_param}/edit
   collection_url             # => /users

Those urls helpers also accepts a hash as options, just as in named routes.

   
   # /projects/1/tasks
   collection_url(:page => 1, :limit => 10) #=> /projects/1/tasks?page=1&limit=10

Another nice thing is that those urls are not guessed during runtime. They are
all created when your application is loaded (except for polymorphic
associations, that relies on Rails polymorphic_url).

Bugs and Feedback
-———————

If you discover any bugs, please send an e-mail to jose.valim@gmail.com
If you just want to give some positive feedback or drop a line, that’s fine too!

Copyright © 2009 José Valim
http://josevalim.blogspot.com/