swift - 在 swift 3 中创建复杂的 NSCompoundPredicate

Question

我想在 swift 3 中创建一个复杂的NSCompoundPredicate，但是，我不知道该怎么做。

假设我有 5 个谓词 (p1,p2,p3,p4,p5)。我想实现以下条件：

compound1 = (p1 AND p2 AND p3) // NSCompoundPredicate(type: .and, 
                              //subpredicates: predicates)
compound2 = (p4 AND p5) // NSCompoundPredicate(type: .and, 
                       //subpredicates: predicates)
compound3 = (compound1 OR compound2) // problem is here

fetchRequest.predicate = compound3

NSCompoundPredicate因为它的第二个参数得到它不想要的 NSPredicates 数组。什么是最好的解决方案？

Answer 1

NSCompoundPredicate继承自NSPredicate，因此您可以将在第一步中创建的复合谓词作为子谓词传递给另一个复合谓词：

let compound1 = NSCompoundPredicate(type: .and, subpredicates: [p1, p2, p3])
let compound2 = NSCompoundPredicate(type: .and, subpredicates: [p4, p5])
let compound3 = NSCompoundPredicate(type: .or, subpredicates: [compound1, compound2])

fetchRequest.predicate = compound3