Rails has_and_belongs_to_many迁移 [英] Rails has_and_belongs_to_many migration

问题描述

我有两个要执行has_and_belongs_to_many关系的模型restaurant和user.

I have two models restaurant and user that I want to perform a has_and_belongs_to_many relationship.

我已经进入模型文件并添加了has_and_belongs_to_many :restaurants和has_and_belongs_to_many :users

I have already gone into the model files and added the has_and_belongs_to_many :restaurants and has_and_belongs_to_many :users

我认为在这一点上我应该能够对Rails 3进行类似的操作.

I assume at this point I should be able to do something like with Rails 3:

rails generate migration ....

但是我尝试过的一切似乎都失败了.我确信这是非常简单的事情，我是Rails的新手，所以我还在学习.

but everything I have tried seems to fail. I'm sure this is something really simple I'm new to rails so I'm still learning.

推荐答案

您需要以字母顺序添加仅包含restaurant_id和user_id(无主键)的单独的联接表. >.

You need to add a separate join table with only a restaurant_id and user_id (no primary key), in alphabetical order.

首先运行您的迁移，然后编辑生成的迁移文件.

First run your migrations, then edit the generated migration file.

路轨3

rails g migration create_restaurants_users_table

路轨4 :

rails g migration create_restaurants_users

路轨5

rails g migration CreateJoinTableRestaurantUser restaurants users

从文档:

如果JoinTable，还有一个生成器将生成联接表 是名称的一部分:

There is also a generator which will produce join tables if JoinTable is part of the name:

---

您的迁移文件(请注意:id => false；这是阻止创建主键的原因):

---

Your migration file (note the :id => false; it's what prevents the creation of a primary key):

路轨3

class CreateRestaurantsUsers < ActiveRecord::Migration
  def self.up
    create_table :restaurants_users, :id => false do |t|
        t.references :restaurant
        t.references :user
    end
    add_index :restaurants_users, [:restaurant_id, :user_id]
    add_index :restaurants_users, :user_id
  end

  def self.down
    drop_table :restaurants_users
  end
end

路轨4

class CreateRestaurantsUsers < ActiveRecord::Migration
  def change
    create_table :restaurants_users, id: false do |t|
      t.belongs_to :restaurant
      t.belongs_to :user
    end
  end
end

t.belongs_to将自动创建必要的索引. def change将自动检测向前或向后迁移，而无需进行上/下迁移.

t.belongs_to will automatically create the necessary indices. def change will auto detect a forward or rollback migration, no need for up/down.

路轨5

create_join_table :restaurants, :users do |t|
  t.index [:restaurant_id, :user_id]
end

注意:还有一个自定义表名称的选项，可以作为参数传递给名为table_name的create_join_table.从文档

Note: There is also an option for a custom table name that can be passed as a parameter to create_join_table called table_name. From the docs

默认情况下，联接表的名称来自于 提供给create_join_table的前两个参数，按字母顺序 命令.要自定义表的名称，请提供:table_name 选项:

By default, the name of the join table comes from the union of the first two arguments provided to create_join_table, in alphabetical order. To customize the name of the table, provide a :table_name option:

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