多对一与多个目标实体

问题描述

这似乎很简单，但我不能正确：

有三个实体： Fruit Vegetable 和 Snack 。 Snack有字段 id ，时间和 food 。食物是指 一个水果或一种蔬菜。所以它基本上是一个多对一/一对多的关系，因为一个小吃总是只有一个食物。但是有多个目标实体。

如何在Doctrine2中映射？

我会在使用之前知道Doctrine2将使用两个字段： food_type 和 food_id 。但如何才能从食物类型到正确的实体连接？我想到一个JoinColumns数组，但是找不到一种方法来连接正确的实体。我还看看映射的超类，因为有一个DiscriminatorColumn，但它也似乎是错误的方法。如果我得到它正确的超类不能是一个实体本身 - 所以我不能创建一个食物实体。

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解决方案

您可以创建一个（抽象）映射的超类名为 Food ，它可以保存水果和蔬菜的一些基本信息。 p>

您的问题的关键字是继承映射，这是它的文档：

然后，您可以在实体关系中引用此映射的超类。

This seems simple but I can't get it right:

There are three entities: Fruit, Vegetable and Snack. Snack has the fields id, time and food. Food is a reference to either one fruit or one vegetable. So it is basically a many-to-one/one-to-many relationship as one snack will always only hold one food. But there is more than one target entity.

How would I map this in Doctrine2?

A simple solution I would have used before knowing Doctrine2 would be to use two fields: food_type and food_id. But how can I make a connection from food type to the correct entity? I thought about an array of JoinColumns but can't find a way to connect the correct entity. I also had a look at mapped superclasses because there is a DiscriminatorColumn, but it also seems to be the wrong approach. If I get it right the superclass can't be an entity itself - so I cannot create a food entity.

Any help is appreciated. I'm sure I am missing something simple here.

解决方案

You can create a (abstract) mapped superclass called Food, which can hold some basic information for Fruit and Vegetable.

The keyword for your question is inheritance mapping, this is the documentation for it: http://doctrine-orm.readthedocs.org/en/latest/reference/inheritance-mapping.html

Then you could reference this mapped superclass in your entity relationship.

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