在验证失败使用的has_many时加入模型：通过 [英] Failing validations in join model when using has_many :through

问题描述

我完全code可以看出，在<一个href="https://github.com/andyw8/simpleform_examples">https://github.com/andyw8/simpleform_examples

My full code can be seen at https://github.com/andyw8/simpleform_examples

我有一个联接模式产品分类用下面的验证：

I have a join model ProductCategory with the following validations:

validates :product, presence: true
validates :category, presence: true

我的产品模式有以下关联：

has_many :product_categories
has_many :categories, through: :product_categories

当我尝试创建一个类，调用 @ product.save 控制器的新产品失败，！

When I try to create a new product with a category, the call to @product.save! in the controller fails with:

Validation failed: Product categories is invalid

当我删除了验证，一切正常和连接模型正确保存。

When I remove the validations, everything works and the join models are saved correctly.

我用 strong_parameters 但是我没有的认为的，应与此相关的问题。

I'm using strong_parameters but I don't think that should be related to this issue.

推荐答案

这是在回调链中的赛车状况。

This is a "racing condition" in the callback chain.

当你创建一个产品它没有它被保存在任何ID，因此也就不存在产品在产品分类<范围/ code>。

When you create a product it doesn't have any id before it is saved, therefore there is no product in the scope of ProductCategory.

Product.new(name: "modern times", category_ids:[1, 2]) #=> #<Product id: nil >

在验证这一阶段（保存之前）， ProductCatgory 不能以它的外键的product_id 指定任何标识。

At that stage of validation (before saving), ProductCatgory cannot assign any id to it's foreign key product_id.

这就是原因，你有关联验证：使验证发生在整个交易的范围

That's the reason you have association validations : so that the validation happens in the scope of the whole transaction

更新：正如评论说您仍然无法保证产品/类presence。有许多方法围绕这取决于你为什么要这么做（通过某种形式如直接进入产品分类）

UPDATE: As said in the comment you still can't ensure presence of a product/category. There's many ways around depending on why you want do this (e.g direct access to ProductCategory through some form)

• 您可以创建一个标志，有验证：产品，presence：的确，如果：？direct_access
• 如果你只能更新它们：验证：产品，presence：真的，在更新
• 在第一个（在products_controller）创建你的产品后添加的类别

• You can create a flag to have validates :product, presence: true, if: :direct_access?
• or if you can only update them: validates :product, presence: true, on: "update"
• create your product first (in the products_controller) and add the categories after

......不过说实在的，这些都是从简单的任何妥协或解决方法 @ product.create（PARAMS）

... But indeed these are all compromises or workarounds from the simple @product.create(params)

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