查找值是否应建模为聚合根？ [英] Should lookup values be modeled as aggregate roots?

问题描述

作为域模型的一部分，假设我有一个 WorkItem 对象。 WorkItem 对象与查找值具有多种关系，例如：

As part of my domain model, lets say I have a WorkItem object. The WorkItem object has several relationships to lookup values such as:

WorkItemType ：

• UserStory


• 错误


• 增强

优先级：

• 高


• 中


• 低

可能还有更多，例如状态，严重程度等...

And there could possibly be more, such as Status, Severity, etc...

DDD指出，如果聚合根中存在某些内容，则不应尝试在聚合根之外访问它。因此，如果我希望能够添加诸如Task之类的新WorkItemTypes或诸如Critical之类的新Priority，这些查找值是否需要是具有其自身存储库的聚合根？这似乎有些矫kill过正，尤其是当它们只是一个键值对时。

DDD states that if something exists within an aggregate root that you shouldn't attempt to access it outside of the aggregate root. So if I want to be able to add new WorkItemTypes like Task, or new Priorities like Critical, do those lookup values need to be aggregate roots with their own repositories? This seems a little overkill especially if they are only a key value pair. How should I allow a user to modify these values and still comply with the aggregate root encapsulation rule?

推荐答案

Landon，我认为我应该如何允许用户修改这些值并仍然遵守聚合根封装规则？唯一的方法是使这些值对聚合根。我知道这可能看起来有些矫，过正，但这是DDD将事情制动成小组件。

Landon, I think that the only way is to make those value pairs aggregate roots. I know that is might look overkill, but that's DDD braking things into small components.

我认为使用存储库是正确方法的原因是：

The reasons why I think using a repository is the right way are:

• 用户需要能够独立于工作项添加这些值对。


• 这些值对不没有本地唯一的身份

请记住，DDD只是一组准则，不是硬道理。如果您认为这是多余的，则可能需要创建一个将对作为值对象返回的查找。如果您没有在应用程序中而是通过数据库添加值对的功能，则可能会特别有效。

Remember that DDD is just a set of guidelines, not hard truths. If you think that this is overkill, you might want to create a lookup that returns the pairs as value objects. This might work out specially if you don't have a feature to add value pairs in the application, but rather through the database.

另外，很好的问题是！有很多关于这种情况的博客文章...但是，并非所有人都同意这样做的最佳方法。

As a side note, good question! There are quite a few blog posts about this situations... But not all agree on the best way to do this.

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