Rails 4模型关联左联接验证ID [英] rails 4 model association left join validate id

问题描述

我已经为此进行了一段时间的争执，我想创建一个LEFT联接条件，所以我有一个Coupon模型，用户可以创建优惠券，但是当他们被分配时，他们可能会分配也可能不会分配给工作他们被认为已执行.我在带有add_reference :jobs, :coupon, index: true索引的优惠券模型上将其设置为has_one :job，但这似乎令人厌烦.我认为今天我的大脑已经炸了……如果使用优惠券，我理想地想确认它是否已分配给有效工作，这就是我使用索引的原因.

I have been battling this for a bit now, I want to create a LEFT join condition, so I have a Coupon model, users can create coupons but they may or may not be assigned to a job, when they are a assigned they are considered executed. I had this setup as has_one :job on the coupon model with a add_reference :jobs, :coupon, index: true index, but this seems borked. I think my brain is fried today… If coupon is used I would ideally like to confirm that it is assigned to valid job, which is why I was working with the index.

class CreateCoupons < ActiveRecord::Migration
  def change
    create_table :coupons do |t|
      t.string :code, limit: 250, null: false
      t.datetime :start_at, null: false
      t.datetime :end_at, null: false
      t.datetime :executed_at
      t.datetime :deleted_at
      t.timestamps null: false
    end

    add_reference :jobs, :coupon, index: true
    add_index :coupons, :deleted_at
    add_index :coupons, :code, unique: true
  end
end

class CreateJobs < ActiveRecord::Migration
  def change
    create_table :jobs do |t|
      t.string :title, limit: 50, null: false
      t.string :slug, limit: 250, null: false
      t.string :location, limit: 100, null: false
      t.string :short_description, limit: 250, null: false
      t.text   :description, null: false
      t.text   :application_process, null: false
      t.boolean :is_featured, default: false
      t.datetime :start_at
      t.datetime :end_at

      t.timestamps null: false
    end

    add_index :jobs, :slug
  end
end

还有模型类...

class Coupon < ActiveRecord::Base
  has_one :job
end

class Job < ActiveRecord::Base
  belongs_to :coupon
end

推荐答案

首先，我要说的是您目前所拥有的并没有什么真正的问题，实际上还不清楚您的问题出在哪里.

Let me start by saying that there's nothing really wrong with what you've got currently, and it's not actually clear what your problem here is.

我实际上将对此建模，将job_id放在coupons表上，即:

I would actually model this the other way around, having job_id on the coupons table, ie.:

add_reference :coupons, :job, index:true

然后...

class Coupon < ActiveRecord:Base
  belongs_to :job
end

最大的优点是，无需查看任何其他表就可以知道是否执行了优惠券，如果job_id为NULL则不执行该优惠券-现在，您需要如何获取优惠券实际上在jobs表上执行SELECT只是为了找出是否存在带有该coupon_id

The biggest advantage with that is that you can know whether your coupon is executed or not without looking at any other table, if job_id is NULL then it's not executed - whereas how you have it now you'd need to actually do a SELECT on the jobs table just to find out if there was a record with that coupon_id

您的executed?方法将变为:

def executed?
  job_id.present?
end

这篇关于Rails 4模型关联左联接验证ID的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！