在阅读DDD之后,我了解到我的用户是实体对象 – 我使用他们的唯一ID来引用它们.
当一个用户“跟随”另一个用户(即形成连接)时,该关系存储在多对多表中.其字段包括FollowerID,TargetID和Status.每个Follower / Target组合只能有两个记录(一个是Active,另一个是Inactive),所以我可以根据它们的属性安全地识别对象.
所以,我认为我的Connection对象是Value Objects,而不是Entity Objects,但我不确定.你能帮我解决这个问题吗？
你是正确的,实体是唯一的,并带有身份的概念(即只有一个唯一的用户可以存在).连接依赖于其他用户实体.它代表了两个用户之间的某些方面.这方面是指是否存在活动或非活动连接.如果不包含用户连接的数据,则连接没有标识.它甚至可能在数据库中拥有它自己的主键,但从域的角度来看,它没有自己的身份.因此,我会说Connection是一个值对象.
为了支持我的结论,Microsoft.Net Architecting Applications for the Enterprise,第187页说：
A value object class represents an entity in the domain that mostly
contains data and lives for the data it contains. A value object is
fully identified by a combination of values it contains. An entity
object, on the other hand, has its own life and rich behavior
regardless of the data it contains. Entity objects are usually objects
with a longer lifetime. A value object represents an aspect of an
entity and can live only in relation to an entity.
另请参阅第189页：
One further comment is needed to explain the difference between entities and value objects. You don’t need a repository or a data mapper for a value object. You need a repository only for an entity. The repository (or the mapper) for a given entity will certainly take care of all value objects that depend on a given entity.