Does association in rails generated automatically?-CodePudding

If I have command and model like this:

Command

$ bin/rails generate model User name:string firstname:string

$ bin/rails genarate model Profile username:string password:string

model generated by rails

class User < ApplicationRecord
  has_one :profile
end

Class Profile < ApplicationRecord
  belongs_to :user
end

Is the 1:1 association in migrate folder generated automatically by rails or I have to implement it myself?

CodePudding user response：

The migration file for Profiles (class CreateProfiles < ActiveRecord::Migration) should have a foreign key declaration like this:

t.references :user, null: false, foreign_key: true

whole code:

create_table :profiles do |t|
  t.string :username
  t.string :password
  t.references :user, null: false, foreign_key: true

  t.timestamps
end

That can also be generated automaticaly with the generator command by adding user:references like so: $ bin/rails genarate model Profile username:string password:string user:references

You can also refer to the Active Record Migrations guide and search for "references" on that page.

CodePudding user response：

ActiveRecord::Associations::ClassMethods does not create database columns automatically. That would actually be a very risky and undesirable feature. You do not want your Rails server to change the DB schema at runtime. Thats what migrations are for.

You can however use the references "type" in the generators (also aliased as belongs_to) which creates a a foreign key column as well as an assocation in the model:

bin/rails g model Profile username:string password:string user:references

class CreateProfiles < ActiveRecord::Migration[7.0]
  def change
    create_table :profiles do |t|
      t.string :username
      t.string :password
      t.references :user, null: false, foreign_key: true
      t.timestamps
    end
  end
end

class Profile < ApplicationRecord
  belongs_to :user
end

There is no equivilent for adding has_one or has_many assocations from generators as they don't actually correspond to a database column on this model.

If you need to add a foreign key column to the table after the fact you do it by generating a migration:

bin/rails g migration AddUserIdToProfiles user:refereces