Rails 可选的belongs_to [英] Rails optional belongs_to

问题描述

我正在编写用于库存管理的 Rails 前端.我希望用户能够注册产品，所以我有:

I'm writing a Rails frontend for inventory management. I want users to be able to register products, so I have:

class User < ActiveRecord::Base
  has_many :products
  # <snip>
end

和

class Product < ActiveRecord::Base
  belongs_to :user
  # <snip>
end

问题在于产品是在用户注册之前创建的.也就是说，调用 Product.create 并让它将 user_id 设置为 nil 是完全可以接受的.但是，正如您所想象的，Rails 并不支持这种开箱即用的功能:

The problem is that products are created prior to being registered by a user. That is, it's perfectly acceptable to call Product.create and just have it set the user_id to nil. As you can imagine, though, Rails doesn't support this out of the box:

> Product.create!
   (0.3ms)  SELECT COUNT(*) FROM "products" WHERE "products"."type" IN ('Product')
   (0.1ms)  begin transaction
   (0.1ms)  rollback transaction
ActiveRecord::RecordInvalid: Validation failed: User can't be blank
    from ~/.rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/validations.rb:56:in `save!'

我想过很多笨拙的变通方法，其中最吸引人的是让 NullUser 子类化 User 并使用它来创建产品.但这似乎仍然是一个黑客.这有什么 Rails 方式?

I've thought about a bunch of kludgey workarounds, the most appealing of which is to have a NullUser subclassing User and use that to create products. But that still seems like a hack. What's the Rails Way with this?

谢谢.

相关迁移:

class AddUseridToProducts < ActiveRecord::Migration
  def change
    add_column :products, :user_id, :integer
  end
end

及以后:

class Changeuseridtobeoptionalforproducts < ActiveRecord::Migration
  def change
    change_column :products, :user_id, :integer, null: true
  end
end

推荐答案

您是否有需要用户在场的验证?如果是这样，请将其删除.

Do you have a validation that requires user be present? If so, remove that.

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