How is this sent to the Show action

Question

I am new to ruby on rails and i want to understand how this piece of code redirect to the show action thanks :

def create
  @article = Article.new(params[:article])
  @article.save

  redirect_to @article
end

Answer 1

I am new to ruby on rails

To understand how it works, you need to understand the nature of Ruby, rather than Rails.

---

OOP

Because Rails is built on top of Ruby, it's an exponent of the object orientated programming pattern - the idea that every element of your application should be geared towards the creation & manipulation of objects:

Although the answer to your question lies in the Rails application of this methodology, its understanding begins in how Ruby gets it to work.

In order to have a truly object orientated experience, Ruby builds classes which are available in memory to manipulate & utilize. These classes are invoked, and have a series of methods which you can use to interact with them.

In the sense of Rails (I'm not super experienced with Ruby), these methods come in two forms:

• Class methods (def self.x)
• Instance methods (def x)

These work to give you the ability to call these methods to manipulate your object as you see fit. For example, if you were creating a game with aliens, you could have @alien.is_visible?

This is the underline structure which Ruby gives us.

---

Rails

Because Rails is built on top of Ruby (Ruby being the language, Rails being the framework), your answer lies in how Rails manipulates the objects you create.

To understand it properly, you need to know that Rails is an MVC (Model View Controller) framework:

As you can see, Rails builds your objects in your Models. This is why you can call @article = Article.find x.

Thus, when you ask how redirect_to @article works, you need to remember that Rails builds its objects in a certain way (IE with a series of base methods - inherited from ActiveRecord::Base).

These methods give each model object a certain structure, which Rails can use within its helpers. This is the case with redirect_to:

          Prefix Verb     URI Pattern                  Controller#Action

        articles GET      /articles(.:format)          articles#index
                 POST     /articles(.:format)          articles#create
     new_article GET      /articles/new(.:format)      articles#new
    edit_article GET      /articles/:id/edit(.:format) articles#edit
         article GET      /articles/:id(.:format)      articles#show
                 PATCH    /articles/:id(.:format)      articles#update
                 PUT      /articles/:id(.:format)      articles#update
                 DELETE   /articles/:id(.:format)      articles#destroy

Rails expects its objects to conform to a certain structure, backed up by CRUD / RESTful routes:

Thus, if you have @article (which is to conform with Rails' model structure, and you have the routes set up as below):

#config/routes.rb
resources :articles

Rails will be able to take your instance of the Article object, and use it to populate the redirect_to route.

--

This is how Rails populates many of its helper methods, including form_for and render. It's intelligent guessing, based on the conventions which govern the framework.

It's why Rails programmers are often eager to point out how "Railsy" their code is.

Answer 2

Basically you have the following route:

Prefix Verb   URI Pattern                  Controller#Action
article GET    /articles/:id(.:format)      articles#show

In order to redirect to the show action of a specific article, you need to end up with a string of the form '/articles/:id', and there are several levels of syntastic sugar to accomplish this:

redirect_to @article
redirect_to article_path(@article)
redirect_to article_path(@article.id)

You could also explicitly specify the path, or even the full URL:

redirect_to "/articles/#{@article.id}"
redirect_to "http://myapp.com/articles/#{@article.id}"

although I wouldn't recommend that.

See the API docs for more ways of using redirect_to

Answer 3

If you define your routes using the Rails convention of defining RESTful routes i.e. resources :articles in your routes.rb file, then redirect_to @article will take you to the show page of this particular @article instance. Rails is doing the underlying magic here.

When you write resources :articles in your routes.rb file, Rails is generating these routes for you automatically:

      Prefix Verb   URI Pattern                  Controller#Action
    articles GET    /articles(.:format)          articles#index
             POST   /articles(.:format)          articles#create
 new_article GET    /articles/new(.:format)      articles#new
edit_article GET    /articles/:id/edit(.:format) articles#edit
     article GET    /articles/:id(.:format)      articles#show
             PATCH  /articles/:id(.:format)      articles#update
             PUT    /articles/:id(.:format)      articles#update
             DELETE /articles/:id(.:format)      articles#destroy

So you have this particular route which is mapped to articles controller's show action:

article GET    /articles/:id(.:format)      articles#show

This route is matched when you do: redirect_to @article and that is why it's taking you to the show page of this @article.

To know more about how RESTful routes works, see this Rails tutorial