Rails 3:belongs_to、has_one 和 Migrations [英] Rails 3: belongs_to, has_one and Migrations

问题描述

我是 Rails 的新手，我是从 Django 背景开始学习的.我已经接受了这样一个事实，即模型和数据库模式在 Rails 在线 Django 中是分开的.但是，我仍在处理迁移问题.

I'm new to Rails, and I'm coming to it from a Django background. I've come to terms with the fact that models and the database schema are separate in Rails, online Django. However, I'm still getting to grips with migrations.

我的问题相当简单 - 如何使用迁移向模型添加关系?例如，我将 Artist 和 Song 作为空模型，它们现在是 ActiveRecord::Base 的子类，没有任何关系.

My question is fairly simple - how do I add a relationship to a model using a migration? For example, I have Artist and Song as empty models that subclass ActiveRecord::Base at the moment, with no relationships whatsoever.

我需要开始这样做:

class Artist < ActiveRecord::Base
  has_many :songs
end

class Song < ActiveRecord::Base
  belongs_to :artist
end

但是如何使用 rails g migrate 更改架构以反映这一点?我使用的是 Rails 3.1.3.

But how do I change the schema to reflect this using rails g migrate? I'm using Rails 3.1.3.

推荐答案

您必须在迁移文件中添加外键，如下所示:

You have to add the foreign key in your migration file, something like this:

def change
  create_table :songs do |t|
    t.references :artist
  end

  add_index :songs, :artist_id
end

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