Ruby on Rails Tutorial Confused about how Params hash works

Question

So I've seen that other people have been confused me about this, and I have read other answers but I'm still confused.

How is information stored and parsed into the params hash during a delete request? I understand how it works in regards to submitting information to it. i.e. when a Put, Post or Get request is issued, I understand that the info is passed via params hash to respective controller action.

However, based on the code below in the user partial (_user.html.erb) :

<li>
    <%= gravatar_for user, size: 52 %>
    <%= link_to user.name, user %>

    <% if current_user.admin? && !current_user?(user) %>
    <%= link_to "delete", user, method: delete,
                            data: {confirm: "You sure?"} %>
                            <% end %>
</li>

And the code in the DESTROY action that is automatically routed to:

def destroy
  User.find(params[:id]).destroy
  flash[:success] = "User destroyed."
  redirect_to users_url
end

I don't understand how the params hash gets the user id stored in it. I'd understand if it were params[:user][:id] since we are posting the user which has its list of attributes. But, I don't get how the id gets stored DIRECTLY into the params hash. This has been bothering me for a while so please any insight would be appreciated.

Answer 1

It's the way how rails works. If you do a rake routes you will see that you get something like DELETE /users/:id.

This means that the user object that you pass as the parameter gets interpreted as :id. When Rails sees this, it will know that it has to look at the ID of the object passed, by convention all the models do have an ID field.

Answer 2

It's based on rails routing model.

If you used resources :user in config/routes.db it will create the following route (you can view it by running rake routes) :

DELETE users/:id

the symbol :id means that whatever you add after users/ while calling url will be set in params as :id. (in the case, for the DELETE HTTP verb)