Multiple belongs_to in ActiveRecord - ruby-on-rails

Question

I am looking to model a messaging system.
At the moment I have two models, User and Message. I wish for there to be multiple associations on a message to a user, the sender and receiver.
This is my active record migration for my Message.
class CreateMessages < ActiveRecord::Migration[5.1]
def change
create_table :messages do |t|
t.string :body
t.belongs_to :sender, :class_name=>'User', :foreign_key=>'sent_from'
t.belongs_to :recipient, :class_name=>'User', :foreign_key=>'sent_to'
t.timestamps
end
end
end
However when I attempt to create a new Message I get the following error:
class DashboardController < ApplicationController
before_action :authenticate_user!
def index
Message.create(body: "Hello World", 1, 2)
end
end
However I get the following error
ActiveRecord::StatementInvalid (SQLite3::SQLException: no such table: main.recipients: INSERT INTO "messages" ("body", "created_at", "updated_at") VALUES (?, ?, ?)):
What am I missing here? What is the best way to model this relationship?

Answer 1

A few things wrong here.
According to the docs, belongs_to (which is an alias for references) in a migration takes the options: :type, :index, :foreign_key, :polymorphic, and :null. There is no :class_name, and :foreign_key should be true or false (defaults to false).
So, your migration should probably look more like:
class CreateMessages < ActiveRecord::Migration[5.1]
def change
create_table :messages do |t|
t.string :body
t.belongs_to :sender
t.belongs_to :recipient
t.timestamps
end
end
end
message.rb will look something like:
class Message < ActiveRecord::Base
belongs_to :sender, class_name: 'User'
belongs_to :recipient, class_name: 'User'
...
end
I don't know why you're creating a Message in the index action of your DashboardController. But, hey, whatever floats your boat.
But, it should probably look more like:
class DashboardController < ApplicationController
before_action :authenticate_user!
def index
Message.create(body: "Hello World", sender_id: 1, recipient_id: 2)
end
end
Or, it might look something like:
class DashboardController < ApplicationController
before_action :authenticate_user!
def index
sender = User.find_by(...)
recipient = User.find_by(...)
Message.create(body: "Hello World", sender: sender, recipient: recipient)
end
end
Rails can be pretty smart, but when you do:
Message.create(body: "Hello World", 1, 2)
it's not so smart to know whether 1 is a sender or a recipient. Same with 2. You need to tell rais which is which.