Question

I’ve a couple of model I’ve made using the scaffold generator.

There are:

rails g scaffold event title:string content:text
rails g scaffold link title:string

I would like that each event has many links, and link belongs to events.

So in the event models I’ve coded:

has_many :links

And inside the link model:

belongs_to :event

Moving on I’ve run:

rake db:migrate

In order build the database. And I’ve made a couple of events using scaffold feature.

Now I’d like to add links directly inside the event’s show>views.

Inside the show.html.erb (inside the view>events dir) I’ve written:

<%= form_for([@event, @event.links.build]) do |f| %>

<p><%= f.text_field %></p>
<p><%= f.submit "Add the link" %></p>
<% end %>

But when I try to visit the show page the browser says:

unknown attribute: event_id 

And it says the error is on this line:

<%= form_for([@event, @event.links.build]) do |f| %>

What I did wrong?

Thanks in advance

Answer 1

You must create the foreign key in your migrations, the event_id, by changing the existing ones or creating a new one.

Since you have already migrate them it’s recommended you create a new one, so it should be something like this

class AddEventForeignKeyToLinks < ActiveRecord::Migration
  def up
    change_table :links do |t|
      t.references :event
    end
  end

  def down
    remove_column :links, :event_id
  end
end

Edit: Don’t forget that to create the migration file you should use the command

rails generate migration AddEventForeignKeyToLinks

Or any other name then AddEventForeignKeyToLinks

---

routes

resources :events do 
  resources :links 
end