Ruby on Rails-rake db：seed中止了

Question

I added to my app the devise gem for logIn. My page is a shop and one user has many orders and I add in model user:

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_many :comandas    #I add this line, comandas = orders in Spanish
end

And in the migrate file of Comandas(orders) I added this:

class CreateComandas < ActiveRecord::Migration[5.0]
  def change
    create_table :comandas do |t|
        t.belongs_to :user, index: true #references to user
        t.float   :total
      t.timestamps
    end
  end
end

And now I'm testing the DB with seeds file but when I add a Comanda to a User this raise me the error that rake is aborted.

My seeds file:

c1 = Comanda.create(total: 100)
u1 = User.find_by email: "aaa@aaa.cat"
u1.comandas << [c1]

I'created the user before.

Error: Screen shot of shell

UPDATE:

I finally found the problem. The problem was that I created all models before add this modification. And when I was adding this relation, Rails didn't change me the database. I checked this going into the sqlite command line and listing the columns of Comandas table. And I saw that the reference to user wasn't here. And decide to drop all database executing this command:

rake db:drop db:create db:migrate

And after I added a user and I run:

rake db:seed 

And works! Thanks to all for the help!

Answer 1

Add user_id in comandas table.

Add new migration to add user_id :

rails g migration AddUserIdToCommando user_id:integer

Answer 2

The Comanda model is not enclosed, but I can guess the possible reason for this behavior.

First, what will probably work, and is more compatible with the actual underlying db model is:

c1 = Comanda.new(total: 100)
u1 = User.find_by email: "aaa@aaa.cat"
c1.user_id = u1.id
c1.save!

The User model has no idea of it's child's foreign key, the Comandas table's 'user_id' column. It's more intuitive to see that the Comanda model is responsible for saving its own db columns.

However I can guess, that due to the fact that recent versions of Rails enforce the belongs_to relation by default, when you try to do -

c1 = Comanda.create(total: 100)

it fails, since by using Comanda.create rather than Comanda.new, you're attempting to create and save a new Comanda object with a nil User relation. You can overcome this by specifying:

belongs_to :user, :optional => true

in your Comanda model, but this will probably break your business model.

The actual error is due to the fact that the first line (create c1) failed, and when processing gets to the last line (commandas << ...), the c1 object is nil or invalid and then the update to the user object fails.

Hope this helps!