确保父模型是一个的has_many一样的：通过协会轨3.2 [英] Ensure parent models are the same for a has_many :through association in rails 3.2

问题描述

我有一个与产品和文件<相关的处父模型/ code>通过的has_many / 模式belongs_to的的关系。在产品和文件模型，然后通过的has_many互相关联：通过通过关系 ProductDocuments 加入的模式。

I have a Department parent model that is associated with a Product and Document model through a has_many / belongs_to relationship. The Product and Document models are then associated to each other through a has_many :through relationship via a ProductDocuments join model.

作为协会的一部分，还有就是产品和文件车型具有相同的<$ C的要求$ C>部门时被互相关联父模型。

As part of the associations there is a requirement that the Product and Document models have the same Department parent model when being associated to each other.

现在我做以下内容：

ProductDocumentsController < ApplicationController
    ...
    def create
        @product = Product.find(params[:product_document][:product_id])
        @document = Document.find(params[:product_document][:document_id])

        if @product.department.id == @document.department.id
            ...
        end
    end
    ...
end

这工作的，但是感觉效率不高，因为它引入了控制器有两个附加的数据库调用。

This works, however it feels inefficient as it introduces two addition database calls in the controller.

没有人知道的一种方法，这可以以更有效的方式来完成，或者通过模型中的验证？

Does anyone know of a way that this can be accomplished in a more efficient way, perhaps through a validation in the model?

任何帮助将大大AP preciated;谢谢！

Any help would be greatly appreciated; thank you!

推荐答案

下面是我的想法。获取铅笔，纸和我一起绘制=）。我已经结束了这样的事情。

Here are my thoughts. Get pencil, paper and draw with me =). I've ended up with something like this.

Department * * * Product
*                   *
*                   *
*                   *
Document * * * ProductDocument

这就是所谓的循环引用的。通常情况下它会导致像你这样的情况 - 其中的表可能无限多领域的平等复杂的验证。那么，我们如何解决这个问题？

And that is something called circular reference. Typically it leads to cases like yours - complex validations of field equality among possibly infinite number of tables. So, how do we fix it?

变种夫妇：

1. 简单地打破环节之一。例如，文件将参照产品孤单。


2. 删除引用处来自产品和文件，并把它在其他地方。例如，进入 ProductDocument （但是，它会被重命名为更合适，因为它会加入三种型号的东西）。

1. Simply break one of the links. For example, Document will reference to Product alone.
2. Remove references to Department from both Product and Document, and put it somewhere else. For example, into ProductDocument (however, it's going to be renamed to something more appropriate since it will join three models).

这就是我能说的现在。

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