Rails的ActiveRecord的::有道验证presence的联想？ [英] Rails ActiveRecord:: Proper way for validating presence on associations?

问题描述

我的模型之间的Rails的关联项目和队列。一个项目的has_many队列。队列必须有一个项目，因此对PROJECT_ID一个presence验证

I have a Rails association between models Project and Queue. A project has_many queues. A queue must have a project, and consequently has a presence validation on project_id

假设我想创建队列一个新的项目。举例来说，这样的事情：

Suppose I want to create a new project WITH queues. For example, something like this:

project = Project.new(valid: param, options: here)
project.queues << Queue.new(other_valid: param, options: here)
project.save!

的保存是要失败的，因为队列失败PROJECT_ID presence验证。

The save is going to fail because the queues fail the project_id presence validation.

我平常丑得到解决这个的方法是创建一个项目，然后加入队列，并包裹了一大堆的事务，因此如果任何部分的过程中失败，它会回退。 ......不知怎的，这似乎难看比它应该是。

My usual ugly way of getting around this is to create a project, then add queues, and wrap the whole lot in a transaction so that if any part of the process fails, it rolls back. ...Somehow that seems uglier than it should be.

那么，有没有击中presence验证创建一个新的项目队列的更优雅的方式，但仍然断言，这些队列必须有一个项目？

So, is there a more graceful way of creating queues on a new project without hitting the presence validation, but still assert that those queues must have a project?

干杯

推荐答案

尝试使用的您的队列协会建立的方法，像这样的：

Try to use the build method on your queues association, like this:

project = Project.new(valid: param, options: here)
project.queues.build(other_valid: param, options: here) //this will build the queue and set its project_id to your current project.
project.save!

只是要确保你的PROJECT_ID具有正确的价值，称 project.save之前插入此行：！

project.queues.each do |queue|
  puts queue.project_id 
end

---

那么，什么是错的与你的code？

---

So what's wrong with your code?

project = Project.new(valid: param, options: here) //build a new project - this is not yet persisted, so your id column is nil
project.queues << Queue.new(other_valid: param, options: here) // this line tries to save the queue to the database, does not wait for you to call project.save!
project.save!

当您拨打：

project.queues << Queue.new(other_valid: param, options: here)`

Rails的尝试到新的队列保存到数据库中，但因为你的项目没有保存， queue.project_id 是零所以你排队验证失败。

Rails tries to save your new queue to the database, but since your project is not saved, queue.project_id is nil so your queue validation fails.

如果您尝试从数据库中获取一个项目（一个持久的项目），您的code将工作没有错误。类似的事情

If you try something similar with a project fetched from the database (a persisted project), your code will work without errors.

如果你仍然想使用类似的东西，添加新的队列就可以了，这样才保存项目：

If you still want to use something similar, save the project before adding a new queue on it, like this:

project = Project.new(valid: param, options: here)

if project.save
  project.queues << Queue.new(other_valid: param, options: here) //this guarantees that project_id exists
end

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