How does articles_path work? (RubyOnRails tutorial)

Question

I am following the official ruby on rails tutorial and I just finished chapter 5.9.

Adding links should be simple but I am majorly confused.

When I type bin/rake routes, I get the following output:

fl4m3ph03n1x: ~/blog $ bin/rake routes
      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
        root GET    /                            welcome#index
fl4m3ph03n1x: ~/blog $  

Which makes sense according to the tutorial.

To make use of this, I have a view:

<h1>New Article</h1>

<%= form_for :article, url: articles_path do |f| %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>

  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>

  <p>
    <%= f.submit %>
  </p>
<% end %>

<%= link_to 'Back', articles_path %>

This view has a submit form and a link in the end. According to ruby, I specify the submit button link in the form by using articles_path in <%= form_for :article, url: articles_path do |f| %>.

I really have no idea how that variable is set, but I will take the bait and accept it. According to the tutorial, when clicking the submit button articles_path will be "POST /articles(.:format) articles#create" by default.

However, in the link <%= link_to 'Back', articles_path %>, articles_path is supposed to redirect us to the index page...

Can someone explain me how the same variable has 2 radically different behaviors in the same View ??

Answer 1

How action view methods work :

link_to default request type is 'GET'.

button_to default request type is 'POST'.

Each generated route has a specific type, which is how rails map different requests to the correct ones.

For form_for action view helper method, it differentiates between 'POST' and 'PUT' automatically depending on whether you passed an instance or not to the form.

you can also explicitly provide the method type for the form by adding

method: 'GET' OR :html => { :method => 'GET' }

** check different syntax capabilities depending on rails version.

Same goes to other methods, so if you want link_to to send post request you have to pass method="POST" to it.

---

**How rails differentiate between index and show actions **

In the generated routes table you may have noticed that index action does NOT need an instance id because it is supposed to list all articles. However, for show, you need to pass an instance to it, because it is supposed to show a specific instance only.

= link_to "index", articles_path
= link_to "show", article_path(article)

NOTICE ::

The two methods is not the same, "articles" and "article", plural vs singular. Even if they were identical in names one of them will take an instance and the other won't.