V1.3: Share Code
Actions as objects have a lot of advantages but they make code sharing less intuitive. This section shares a few techniques to make this possible.
In our settings (
apps/web/application.rb), there is a code block that allows us to share the code for all the actions of our application.
When an action includes the
Web::Action module, that block code is yielded within the context of that class.
This is heavily inspired by Ruby Module and its
Imagine we want to check if the current request comes from an authenticated user.
We craft a module in
# apps/web/controllers/authentication.rb module Web module Authentication def self.included(action) action.class_eval do before :authenticate! expose :current_user end end private def authenticate! halt 401 unless authenticated? end def authenticated? !!current_user end def current_user @current_user ||= UserRepository.new.find(session[:user_id]) end end end
Once included by an action, it will set a before callback that executes
:authenticate! for each request.
If not logged in, a
401 is returned, otherwise the flow can go ahead and hit
It also exposes
current_user for all the views (see Exposures).
It will be really tedious to include this module for all the actions of our app.
We can use
controller.prepare for the scope.
# apps/web/application.rb require_relative './controllers/authentication' module Web class Application < Hanami::Application configure do controller.prepare do include Web::Authentication end end end end
Code included via
prepare is available for ALL the actions of an application.
Skipping A Callback
Let’s say we have included
Authentication globally, but want to skip the execution of its callback for certain resources.
A typical use case is to redirect unauthenticated requests to our sign in form.
The solution is really simple and elegant at the same time: override that method.
# apps/web/controllers/sessions/new.rb module Web module Controllers module Sessions class New include Web::Action def call(params) # ... end private def authenticate! # no-op end end end end end
The action will still try to invoke
:authenticate!, because, technically speaking, callbacks execution can’t be skipped.
But if we override that method with an empty implementation, it does nothing and our non-signedin users can reach the wanted resource.
Imagine we have a RESTful resource named
There are several actions (
destroy) which need to find a specific book to perform their job.
What if we want to DRY the code of all these actions? Ruby comes to our rescue.
# apps/web/controllers/books/set_book.rb module Web module Controllers module Books module SetBook def self.included(action) action.class_eval do before :set_book end end private def set_book @book = BookRepository.new.find(params[:id]) halt 404 if @book.nil? end end end end end
We have defined a module for our behavior to share. Let’s include it in all the actions that need it.
# apps/web/controllers/books/update.rb require_relative './set_book' module Web module Controllers module Books class Update include Web::Action include SetBook def call(params) # ... end end end end end