两个belongs_to的关联迁移同型号 [英] Same Model for Two belongs_to Associations migration
问题描述
我如何创建一个具有两个引用到相同型号的模型迁移。
How do I create a migration for a model that has two references to the same model.
我有两个角色,买方和卖方的用户模型,我也有一个销售模式,所以每个销售应该有一个买家和一个卖方。
I have a user model with two roles, buyer and seller, I also have a sales model so each sale should have one buyer and one seller.
我见过这个答案那就表明我的销售模型应该看起来像
I've seen this answer that would suggest my sales model should look like
class Sale < ActiveRecord::Base
belongs_to :buyer, :class_name => 'User', :foreign_key => 'buyer_id'
belongs_to :seller, :class_name => 'User', :foreign_key => 'seller_id'
end
但我不知道如何创建的迁移和得到它的工作...!
but I don't know how to create the migration and get it to work...!
推荐答案
您必须创建以下迁移:
rails g migration AddBuyerAndSellerToSales buyer:references seller:references
这应该创建以下迁移文件:
This should create the following migration file:
class AddBuyerAndSellerToSales < ActiveRecord::Migration
def change
add_reference :sales, :buyer, index: true, foreign_key: true
add_reference :sales, :seller, index: true, foreign_key: true
end
end
如果您使用的数据库引擎如PostgreSQL,你必须告诉引擎哪个表的外键将指向。
If you use a database engine like PostgreSQL you have to tell the engine to which table the foreign key will point.
class AddBuyerAndSellerToSales < ActiveRecord::Migration
def change
add_reference :sales, :buyer, index: true # foreign_key: true <= remove this!
add_reference :sales, :seller, index: true # foreign_key: true <= remove this!
add_foreign_key :sales, :users, column: :buyer_id
add_foreign_key :sales, :users, column: :seller_id
end
end
希望这有助于!
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