Question

I had a general question of what is going on when code like this runs:

<%= form_for(current_user.favorite_relationships.find_by_lesson_id(@lesson),
             html: {method: :delete},
             remote: true) do |f| %>
             <div><%= f.hidden_field :lesson_id %></div>
  <%= f.submit "Unfavorite", class: "btn btn-large" %>
<% end %>

specifically the very first line of code. i usually see some form of instance variable instead of

current_user.favorite_relationships.find_by_lesson_id

I can assume that this will go into the FavoriteRelationship controller’s destroy action. Is there anything else someone can infer from that form above? Like what will be available or gets passed in the destroy action?

Answer 1

Presumably, the controller has supplied a Lesson object to the view through the variable @lesson. Your current user, a User object, presumably has_many :favorite_relationships, which in turn belongs_to :lesson, meaning there is a field within the favorite_relationships table called lesson_id.

Rails builds “magic” finder methods for your models for the fields it contains. If a model has a lesson_id field, Rails provides a find_by_lesson_id helper. Rails is smart enough to extract @lesson.id when you pass it an actual Lesson object instead of an integer.

The net result is that an object of type FavoriteRelationship is being passed into the form_for helper. This is no different than finding the object in the controller and passing it to the view via a (for example) @favorite_relationship variable.

what will be available or gets passed in the destroy action?

The only thing available to the controller on the subsequent request to the FavoriteRelationship’s destroy route is the id of the object to destroy. You’ll be able to access it via params[:id].