NSPredicate的2级钻取？ [英] NSPredicate for 2-level drill-down?

问题描述

核心数据实体A与实体B具有一对多关系，其与实体C具有一对多关系，其具有两个属性：类型和值。

A core data entity A has a to-many relationship to entity B, which has a to-many relationship with entity C, which has two attributes:type and value.

A = >> B = >> C
（So：A.Bs.Cs.type，A.Bs.Cs.value）

A =>> B =>> C (So: A.Bs.Cs.type, A.Bs.Cs.value)

什么是 NSArray 过滤谓词所有A的任何B有任何C（类型=='test1'&&值=='test2'）？

Whats an NSArray filter predicate for all A's that have any B that has any C that has (type=='test1' && value=='test2')?

我看到的子查询示例只有1级深度。

The subquery samples I've seen only go 1 level deep.

c> [NSCompoundPredicate andPredicateWithSubpredicates：]
with subpredicate 1）ANY Bs.Cs.type =='test1'和subpredicate 2）ANY Bs.Cs.value =='test2 '，但不返回任何内容。

I also tried [NSCompoundPredicate andPredicateWithSubpredicates:] with subpredicate 1) "ANY Bs.Cs.type=='test1'" and subpredicate 2) "ANY Bs.Cs.value=='test2'", but nothing is returned.

是的，我看过 NSPredicate

推荐答案

您需要使用 NSExpression + expressionForSubquery：usingIteratorVariable：predicate：或其中记录的表达式语法。

You need to use NSExpression +expressionForSubquery:usingIteratorVariable:predicate: or the expression syntax documented there.

我认为对于你的情况，

I think for your case it would be something like

(SUBQUERY(Bs, $b, 
   SUBQUERY($b.Cs, $c, $c.type=='text1' && $c.value='test2').@count != 0
 ).@count != 0)

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