Inherited Resources

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.

In addition to making your controllers follow a pattern, it helps you to write better code by following fat models and skinny controllers convention. There are two screencasts available besides this README:

• http://railscasts.com/episodes/230-inherited-resources
• http://akitaonrails.com/2009/09/01/screencast-real-thin-restful-controllers-with-inherited-resources

Installation

Rails 3

You can let bundler install Inherited Resources by adding this line to your application's Gemfile:

gem 'inherited_resources'

And then execute:

$ bundle install

Or install it yourself with:

$ gem install inherited_resources

Rails 2.3.x

If you want to use the Rails 2.3.x version, you should install:

$ gem install inherited_resources --version=1.0.6

Or checkout from the v1.0 branch:

http://github.com/josevalim/inherited_resources/tree/v1.0

HasScope

Since Inherited Resources 1.0, has_scope is not part of its core anymore but a gem dependency. Be sure to check the documentation to see how you can use it:

• http://github.com/plataformatec/has_scope

And it can be installed as:

$ gem install has_scope

Responders

Since Inherited Resources 1.0, responders are not part of its core anymore, but is set as Inherited Resources dependency and it's used by default by InheritedResources controllers. Be sure to check the documentation to see how it will change your application:

• http://github.com/plataformatec/responders

And it can be installed with:

$ gem install responders

Using responders will set the flash message to :notice and :alert. You can change that through the following configuration value:

InheritedResources.flash_keys = [ :success, :failure ]

Notice the CollectionResponder won't work with InheritedResources, as InheritedResources hardcodes the redirect path based on the current scope (like belongs to, polymorphic associations, etc).

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 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 checks 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 in your controller class scope:

class AccountsController < ApplicationController
  inherit_resources
end

One reason to use the inherit_resources macro would be to ensure that your controller never responds with the html mime-type. InheritedResources::Base already responds to :html, and the respond_to macro is strictly additive. Therefore, if you want to create a controller that, for example, responds ONLY via :js, you will have write it this way:

class AccountsController < ApplicationController
  respond_to :js
  inherit_resources
end

Overwriting defaults

Whenever you inherit from InheritedResources, several defaults are assumed. For example you can have an AccountsController for account management while the resource is a 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(:page => params[:page])
    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 by 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. 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

Since most of the time when you change a create, update or destroy action you do so because you want to to change its redirect url, a shortcut is provided. So you can do:

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

If you simply want to change the flash message for a particular action, you can pass the message to the parent action using the keys :notice and :alert (as you would with flash):

class ProjectsController < InheritedResources::Base
  def create
    create!(:notice => "Dude! Nice job creating that project.")
  end
end

You can still pass the block to change the redirect, as mentioned above:

class ProjectsController < InheritedResources::Base
  def create
    create!(:notice => "Dude! Nice job creating that project.") { 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, it's 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 too 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.

Smart redirects

Although the syntax above is a nice shortcut, you won't need to do it frequently because (since version 1.2) Inherited Resources has smart redirects. Redirects in actions calculates depending on the existent controller methods.

Redirects in create and update actions calculates in the following order: resource_url, collection_url, parent_url (which we are going to see later), and root_url. Redirect in destroy action calculate in following order collection_url, parent_url, root_url.

Example:

class ButtonsController < InheritedResources::Base
  belongs_to :window
  actions :all, :except => [:show, :index]
end

This controller redirect to parent window after all CUD actions.

Success and failure scenarios on destroy

The destroy action can also fail, this usually happens when you have a before_destroy callback in your model which returns false. However, in order to tell InheritedResources that it really failed, you need to add errors to your model. So your before_destroy callback on the model should be something like this:

def before_destroy
  if cant_be_destroyed?
    errors.add(:base, "not allowed")
    false
  end
end

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 CommentsController < 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

Right now, Inherited Resources is limited and does not allow you to have two polymorphic associations nested.

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 CommentsController < 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 resource of current controller as singleton, you just have to give the :singleton option in defaults.

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

So now you can use urls like "/projects/1/manager".

In the case of nested resources (when some of the can be singletons) you can declare it separately

class WorkersController < InheritedResources::Base
  #defaults :singleton => true #if you have only single worker
  belongs_to :project
  belongs_to :manager, :singleton => true
end

This is correspond urls like "/projects/1/manager/workers/1".

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

Namespaced Controllers

Namespaced controllers works out the box.

class Forum::PostsController < InheritedResources::Base
end

Inherited Resources prioritizes the default resource class for the namespaced controller in this order:

Forum::Post
ForumPost
Post

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
parent_url                 # => /posts/1

# /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
parent_url                 # => /projects/1

# /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
parent_url                 # => /

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

In polymorphic cases, you can also give the parent as parameter to collection_url.

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).

Custom actions

Since version 1.2, Inherited Resources allows you to define custom actions in controller:

class ButtonsController < InheritedResources::Base
  custom_actions :resource => :delete, :collection => :search
end

This code creates delete and search actions in controller (they behaves like show and index actions accordingly). Also, it will produce delete_resource_{path,url} and search_resources_{path,url} url helpers.

What about views?

Sometimes just DRYing up the controllers is not enough. If you need to DRY up your views, check this Wiki page:

https://github.com/josevalim/inherited_resources/wiki/Views-Inheritance

Notice that Rails 3.1 ships with view inheritance built-in.

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 module 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

Strong Parameters

If your controller defines a method named permitted_params, InheritedResources will call it where it would normally call params. This allows for easy integration with the strong_parameters gem:

def permitted_params
  params.permit(:widget => [:permitted_field, :other_permitted_field])
end

Note that this doesn't work if you use strong_parameters' require method instead of permit, because whereas permit returns the entire sanitized parameter hash, require returns only the sanitized params below the parameter you required.

If you need params.require you can do it like this:

def permitted_params
  {:widget => params.require(:widget).permit(:permitted_field, :other_permitted_field)}
end

Or better yet just override #build_resource_params directly:

def build_resource_params
  [params.require(:widget).permit(:permitted_field, :other_permitted_field)]
end

Bugs and Feedback

If you discover any bugs, please describe it in the issues tracker, including Rails and InheritedResources versions.

Questions are better handled on StackOverflow.

Copyright (c) 2009-2012 José Valim http://blog.plataformatec.com.br See the attached MIT License.