针对特定集合的多对多关系核心数据查询

Question

public enum Ability: String {
  case newcomer = "Newcomer"
  case beginner = "Beginner"
  case intermediate = "Intermediate"
  case advanced = "Advanced"
}

public enum Group: String {
  case solo = "Solo"
  case duo = "Duo"
  case team = "Team"
}

我想找到符合以下条件的所有表演。

ability == "Beginner"
group == "Duo"
performers == "Jane Davies" && "Alice Evans"

The documentation表示不支持核心数据中的聚合操作，这是令人惊讶的。这方面的问题一直是asked before，建议使用＆＃39; Any＆＃39;。

根据我的理解，＆＃39;任何＆＃39;将返回包括＆＃39; Jane＆＃39;或者＆＃39; Alice＆＃39;或者＆＃39;简＆amp;爱丽丝＆＃39;对？我只想要包括＆amp; Jane＆amp; amp;爱丽丝＆＃39;

如何为此查询编写谓词？

由于

Answer 1

使用（不同的） Performer 对象列表，以下谓词应该工作 查找与这些对象完全相关的所有 Performance 对象 表演者：

let perf1 = ... // Performer object for "Jane Davies"
let perf2 = ... // Performer object for "Alice Evans"
let list = [perf1, perf2]

let predicate = NSPredicate(format: "performers.@count = %ld AND ALL performers in %@", list.count, list)

但显然不是。解决方法是使用SUBQUERY：

let predicate = NSPredicate(format: "performers.@count = %ld AND SUBQUERY(performers, $p, $p in %@).@count = %ld",
      list.count, list, list.count)