php 带有额外字段的 Doctrine 2 和多对多链接表

Doctrine 2 and Many-to-many link table with an extra field

提问by Henry van Megen

(Sorry for my incoherent question: I tried to answer some questions as I was writing this post, but here it is:)

（抱歉我的问题语无伦次：我在写这篇文章时试图回答一些问题，但在这里：）

I'm trying to create a database model with a many-to-many relationship inside a link table, but which also has a value per link, in this case a stock-keeping table. (this is a basic example for more problems I'm having, but I thought I'd just test it with this before I would continue).

我正在尝试在链接表中创建一个具有多对多关系的数据库模型，但每个链接也有一个值，在这种情况下是一个库存表。（这是我遇到的更多问题的基本示例，但我想我会在继续之前用它进行测试）。

I've used exportmwbto generate the two Entities Store and Product for this simple example, both are displayed below.

我已经使用exportmwb为这个简单的例子生成了两个实体商店和产品，两者都显示在下面。

However, the problem now is that I can't figure out how to access the stock.amount value (signed int, as it can be negative) using Doctrine. Also, when I try to create the tables using doctrine's orm:schema-tool:create function

但是，现在的问题是我无法弄清楚如何使用 Doctrine 访问 stock.amount 值（有符号整数，因为它可以是负数）。此外，当我尝试使用学说的 orm:schema-tool:create 函数创建表时

This yielded only two Entities and three tables, one as a link table without values and two data tables, as many-to-many relationships aren't entities themselves so I can only have Product and Store as an entity.

这仅产生了两个实体和三个表，一个作为没有值的链接表和两个数据表，因为多对多关系本身不是实体，所以我只能将 Product 和 Store 作为实体。

So, logically, I tried changing my database model to have stock as a separate table with relationships to store and product. I also rewrote the fieldnames just to be able to exclude that as a source of the problem:

因此，从逻辑上讲，我尝试更改我的数据库模型，将库存作为一个单独的表，并与商店和产品建立关系。我还重写了字段名，以便能够将其排除为问题的根源：

Then what I found was that I still didn't get a Stock entity... and the database itself didn't have an 'amount'-field.

然后我发现我仍然没有得到 Stock 实体……而且数据库本身没有“金额”字段。

I really needed to be able to bind these stores and products together in a stock table (among other things)... so just adding the stock on the product itself isn't an option.

我真的需要能够将这些商店和产品绑定到一个库存表中（除其他外）......所以只在产品本身上添加库存不是一种选择。

root@hdev:/var/www/test/library# php doctrine.php orm:info
Found 2 mapped entities:
[OK]   Entity\Product
[OK]   Entity\Store

And when I create the database, it still doesn't give me the right fields in the stock table:

当我创建数据库时，它仍然没有给我股票表中的正确字段：

So, looking up some things here, I found out that many-to-many connections aren't entities and thus cannot have values. So I tried changing it to a separate table with relationships to the others, but it still didn't work.

所以，在这里查找一些东西，我发现多对多连接不是实体，因此不能有值。因此，我尝试将其更改为与其他表有关系的单独表，但仍然无效。

What am I doing wrong here?

我在这里做错了什么？

回答by Ocramius

A Many-To-Many association with additional values is not a Many-To-Many, but is indeed a new entity, since it now has an identifier (the two relations to the connected entities) and values.

具有附加值的多对多关联不是多对多，但确实是一个新实体，因为它现在具有标识符（与连接实体的两个关系）和值。

That's also the reason why Many-To-Many associations are so rare: you tend to store additional properties in them, such as sorting, amount, etc.

这也是为什么许多-to-many关联是如此罕见：你会存储在他们的附加属性，如sorting，amount等。

What you probably need is something like following (I made both relations bidirectional, consider making at least one of them uni-directional):

您可能需要的是以下内容（我将两个关系设为双向，考虑至少将其中一个设为单向）：

Product:

产品：

namespace Entity;

use Doctrine\ORM\Mapping as ORM;

/** @ORM\Table(name="product") @ORM\Entity() */
class Product
{
    /** @ORM\Id() @ORM\Column(type="integer") */
    protected $id;

    /** ORM\Column(name="product_name", type="string", length=50, nullable=false) */
    protected $name;

    /** @ORM\OneToMany(targetEntity="Entity\Stock", mappedBy="product") */
    protected $stockProducts;
}

Store:

店铺：

namespace Entity;

use Doctrine\ORM\Mapping as ORM;

/** @ORM\Table(name="store") @ORM\Entity() */
class Store
{
    /** @ORM\Id() @ORM\Column(type="integer") */
    protected $id;

    /** ORM\Column(name="store_name", type="string", length=50, nullable=false) */
    protected $name;

    /** @ORM\OneToMany(targetEntity="Entity\Stock", mappedBy="store") */
    protected $stockProducts;
}

Stock:

库存：

namespace Entity;

use Doctrine\ORM\Mapping as ORM;

/** @ORM\Table(name="stock") @ORM\Entity() */
class Stock
{
    /** ORM\Column(type="integer") */
    protected $amount;

    /** 
     * @ORM\Id()
     * @ORM\ManyToOne(targetEntity="Entity\Store", inversedBy="stockProducts") 
     * @ORM\JoinColumn(name="store_id", referencedColumnName="id", nullable=false) 
     */
    protected $store;

    /** 
     * @ORM\Id()
     * @ORM\ManyToOne(targetEntity="Entity\Product", inversedBy="stockProducts") 
     * @ORM\JoinColumn(name="product_id", referencedColumnName="id", nullable=false) 
     */
    protected $product;
}

回答by timdev

Doctrine handles many-to-many relationships just fine.

Doctrine 可以很好地处理多对多关系。

The problem that you're having is that you don't need a simple ManyToMany association, because associations can't have "extra" data.

您遇到的问题是您不需要简单的多对多关联，因为关联不能有“额外”数据。

Your middle (stock) table, since it contains more than product_id and store_id, needs its own entity to model that extra data.

您的中间（库存）表，因为它包含的不仅仅是 product_id 和 store_id，需要它自己的实体来建模额外的数据。

So you really want three classes of entity:

所以你真的想要三类实体：

• Product
• StockLevel
• Store

• 产品
• 库存水平
• 店铺

and two associations:

和两个协会：

• Product oneToMany StockLevel
• Store oneToMany StockLevel

• 产品一对多库存水平
• 存储 oneToMany StockLevel