问题
I have been using Core Data to model my database. I have 2 entities that are in many to many relationship. Each person can have many addresses, and on each address multiple persons can live.
Now i would like to add property to this relationship. For example one person - address will have label home, other person - address can will have label mama's place.
I can't add this property on address entity, because same address will have different labels for different persons.
Since relationships are modeled like NSSets, I don't see a way to do what I want.
Can this be somehow done?
回答1:
It is not possible to add attributes to a many-many relationship directly. The Apple-recommended approach (see "Modelling a relationship based on its semantics" in the CoreData Programming Guide) is to replace the many-many relationship with an intermediate entity, to which you add the attributes. Each of your existing entities will have a one-many relationship with the new entity.
In your case, you might have something like this:
Person <--->> PersonAddressDetails <<---> Address
You can then add the label attribute to the PersonAddressDetails entity.
来源：https://stackoverflow.com/questions/47225873/adding-properties-to-many-to-many-relationship