API
Controller is a lightweight version of ActionController::Base
, created for applications that don't require all functionalities that a complete Rails controller provides, allowing you to create controllers with just the features that you need for API
only applications.
An API
Controller is different from a normal controller in the sense that by default it doesn't include a number of features that are usually required by browser access only: layouts and templates rendering, flash, assets, and so on. This makes the entire controller stack thinner, suitable for API
applications. It doesn't mean you won't have such features if you need them: they're all available for you to include in your application, they're just not part of the default API
controller stack.
Normally, ApplicationController
is the only controller that inherits from ActionController::API
. All other controllers in turn inherit from ApplicationController
.
A sample controller could look like this:
class PostsController < ApplicationController
def index
posts = Post.all
render json: posts
end
end
Request, response, and parameters objects all work the exact same way as ActionController::Base
.
Renders
The default API
Controller stack includes all renderers, which means you can use render :json
and brothers freely in your controllers. Keep in mind that templates are not going to be rendered, so you need to ensure your controller is calling either render
or redirect_to
in all actions, otherwise it will return 204 No Content.
def show
post = Post.find(params[:id])
render json: post
end
Redirects
Redirects are used to move from one action to another. You can use the redirect_to
method in your controllers in the same way as in ActionController::Base
. For example:
def create
redirect_to root_url and return if not_authorized?
# do stuff here
end
Adding New Behavior
In some scenarios you may want to add back some functionality provided by ActionController::Base
that is not present by default in ActionController::API
, for instance MimeResponds
. This module gives you the respond_to
method. Adding it is quite simple, you just need to include the module in a specific controller or in ApplicationController
in case you want it available in your entire application:
class ApplicationController < ActionController::API
include ActionController::MimeResponds
end
class PostsController < ApplicationController
def index
posts = Post.all
respond_to do |format|
format.json { render json: posts }
format.xml { render xml: posts }
end
end
end
Make sure to check the modules included in ActionController::Base
if you want to use any other functionality that is not provided by ActionController::API
out of the box.
Constants
MODULES | = | [ AbstractController::Rendering, UrlFor, Redirecting, ApiRendering, Renderers::All, ConditionalGet, BasicImplicitRender, StrongParameters, DataStreaming, DefaultHeaders, Logging, # Before callbacks should also be executed as early as possible, so # also include them at the bottom. AbstractController::Callbacks, # Append rescue at the bottom to wrap as much as possible. Rescue, # Add instrumentations hooks at the bottom, to ensure they instrument # all the methods properly. Instrumentation, # Params wrapper should come before instrumentation so they are # properly showed in logs ParamsWrapper ] |
Class Public methods
without_modules(*modules) Link
Shortcut helper that returns all the ActionController::API
modules except the ones passed as arguments:
class MyAPIBaseController < ActionController::Metal
ActionController::API.without_modules(:UrlFor).each do |left|
include left
end
end
This gives better control over what you want to exclude and makes it easier to create an API
controller class, instead of listing the modules required manually.