问题描述
在许多ddd示例中，我们有一个简单的示例：
In many ddd examples we have a simple:
Order（聚合根[AR]）
和
OrderLine（聚合成员[AM ]）
Order (aggregate root [AR])and OrderLine (aggregate member [AM])
+
发票（总根[AR]）
和
InvoiceLine（总成员[AM]）
Invoice (aggregate root [AR])and InvoiceLine (aggregate member [AM])
在这些示例中，我们在订单上开具发票，因此它是从一个AR（发票）直接引用到另一个（订单）的显然是正确的。
In that examples we issue an invoice on order so it is direct reference from one AR (Invoice) to another (Order) which is clearly correct.
但是，在我看来，情况更复杂：
However, in my case things are more complicated:
我们在许多订单行上开具发票
We issue an Invoice on many OrderLines from different Orders.
因此，在一张发票上，我们有：
InvoiceLine＃1引用了订单＃1的OrderLine＃1，
是另一张InvoiceLine ＃2引用OrderLine＃2（来自另一个Order＃2）
So on one Invoice, we have:InvoiceLine #1 referencing to OrderLine #1 from Order #1, another InvoiceLine #2 referencing to OrderLine #2 (from another Order #2)
，例如，没有InvoiceLine引用Order＃1的OrderLine＃2。
and, for example, there is no InvoiceLine referencing to OrderLine#2 from Order #1.
如何解决这种情况？
似乎我们必须在InvoiceLine中保留对OrderLine的引用，这是不正确的，afaik。但我没有其他想法：/
It seems like we have to hold reference to OrderLine in InvoiceLine which is not correct, afaik. But I have no other ideas :/
在此先感谢您提出任何建议。
Thanks in advance for any suggestions.
推荐答案
您不应持有从一个AR到另一个AR的真实对象实例引用。任何实体引用都应该是瞬态的。
You should not hold real object instance references from one AR to another. Any entity references should be transient.
您应该只存储标识符。
在您的情况下，您可以存储相关InvoiceLine条目上的订单ID和OrderLine号。甚至可能是一个价值对象。
In your case you could be storing the Order ID and OrderLine Number on the relevant InvoiceLine entries. It may even be a value object.
通过这种方式，当您从发票库中获取发票AR时，就不会遇到任何对象检索问题。
In this way you are not faced with any object retrieval issues when you get you Invoice AR from its repository.
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