NSPredicate带有！=? [英] NSPredicate with a !=?

问题描述

我有核心数据实体人员和边界.他们之间存在多对多关系(每个人可以有很多边界，每个边界可以有很多人).

I have Core Data Entities Person and Boundary. They have a many-to-many relationship (each person can have many boundaries, and each boundary can have many persons).

我正在尝试创建一个列表，列出Fred Fred也没有任何关系.

I am trying to create a list of what boundaries Person Fred doesn't have a relationship too.

Person *person = [Person MR_findFirstByAttribute:@"name" withValue:@"Fred"];
DLog(@"person.boundaries.count: %d", person.boundaries.count);

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY persons != %@", person];

DLog(@"testBoundaries.count: %d", [Boundary MR_countOfEntitiesWithPredicate:predicate]);

我在数据库中有47个边界，Fred可以看到所有47个边界.因此，我希望我的提取操作将返回0:

I have 47 boundaries in the database, and Fred can see all 47. So I expect my fetch to return 0:

DEBUG | -[LoginViewController viewDidLoad] | person.boundaries.count: 47
DEBUG | -[LoginViewController viewDidLoad] | testBoundaries.count: 47

我的谓词怎么了?

推荐答案

[NSPredicate predicateWithFormat:@"ANY persons != %@", fred]

查找与Fred以外的任何其他人相关的所有对象.您想要的是

finds all objects that are related to any person other that Fred. What you want is

[NSPredicate predicateWithFormat:@"NOT(ANY persons = %@)", fred]

，并且此应该返回与Fred无关的所有对象.

and this should return all objects that are not related to Fred.

但是，似乎有一个核心数据错误，"NOT ANY"或"NONE"无法正常工作 在谓词中 比较 NSPredicate聚合运算与无.解决方法是使用SUBQUERY:

However, there seems to be a Core Data bug that "NOT ANY" or "NONE" do not work correctly in a predicate, compare NSPredicate Aggregate Operations with NONE. The workaround is to use a SUBQUERY:

[NSPredicate predicateWithFormat:@"SUBQUERY(persons, $p, $p == %@).@count == 0", fred]

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