== 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.

Plus, making your controllers follow a pattern, it helps you to write better
code by following fat models and skinny controllers convention. There is
a screencast made by Fabio Akita about its features:

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

This Inherited Resources branch is tested and compatible with Rails 2.3.x.

== Installation

Inherited Resources is available as gem on Gemcutter, so just run the following:

    sudo gem install inherited_resources --version=1.0.3

If you want it as plugin, just do:

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

=== HasScope

Since Inherited Resources 1.0, has_scope is not part of its core anymore.
However, if you are using has_scope in your application, Inherited Resources
will handle all the required hooks automatically.

has_scope gem is available at:

  http://github.com/plataformatec/has_scope

And can be installed as:

  sudo 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 as:

  sudo 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 ]

== Rspec known bug

Rspec monkey patches a couple of controller methods in a way that Controller specs
(with integrate views true or false) and Inherited Resources are not compatible.

However, since your controllers inherit from InheritedResources::Base, they are
already unit-tested in the plugin, so there is no need to test them again in Rspec.

You should test things like url redirection and associations in your integration
specs.

== 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 in your controller class scope:

    class AccountsController < ApplicationController
      inherit_resources
    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(: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 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

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.

== 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

== 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

== 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

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 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
    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).

== Bugs and Feedback

If you discover any bugs or want to drop a line, join us in the mailing list:

http://groups.google.com/group/inherited_resources

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