用于一对多关系的CoreData谓词 [英] CoreData predicate for one to many relationship

问题描述

我有两个实体:A和B. A的每个元素可以具有B的更多元素(一对多).

I have two entity: A and B. Every element of A can have more elements of B (one to many).

现在我有一个项目A，在这个项目中，我要取一个项目B(包含在A中)，它具有B.field ="myParameter".

Now I have an item of A and I would to take, in this item, one item B (contained in A) that it has B.field = "myParameter".

如何为此生成谓词?

推荐答案

您可能正在寻找(已通过 MagicalRecord 测试):

You may be looking for that (tested with MagicalRecord):

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(field LIKE %@) AND (isLinkedToAObject == %@)", myFieldParameter, objectA];

使用: ClassB具有属性isLinkedToAObject可以将其链接到ClassA.

With: ClassB has a property isLinkedToAObject to link it to ClassA.

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