核心数据：忽略对多谓词

Question

我有 Group <-->> Member 关系。在 class Group: NSManagedObject { 我有以下属性：

@NSManaged public var members: Set<Member>

 public var status: Int16 {
    set {
        self.willChangeValue(forKey: "status")
        self.setPrimitiveValue(newValue, forKey: "status")
        self.didChangeValue(forKey: "status")
        self.members.removeAll()
    }
    get {
        self.willAccessValue(forKey: "status")
        var status: Int16 = 0
        if let statusKey = self.primitiveValue(forKey: "status") as? Int16 {
            self.didAccessValue(forKey: "status")
            status = statusKey
        }
        return status
    }
}

在 class Member: NSManagedObject 我有以下属性：

@NSManaged public var memberOf: Group?
@NSManaged public var status: Int16

要求：过滤基于： if Groups.status = 1 AND member.status = 1（对于每个成员）

我有以下代码：

     let statusPredicate = NSPredicate(format: "status == %@", NSNumber(integerLiteral: 1))
     let statusMemberPredicate = NSPredicate(format: "ANY members.status == %d", 1)
     let compoundPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.and, subpredicates: [statusPredicate, statusMemberPredicate])
     print("compoundPredicate \(compoundPredicate)")

     let requestGroups: NSFetchRequest<Group> = NSFetchRequest()
     requestGroups.entity = Group.entity()
     requestGroups.predicate = compoundPredicate
     requestGroups.returnsObjectsAsFaults = false
     requestGroups.fetchBatchSize = 20
     frcGroup = NSFetchedResultsController(fetchRequest: requestGroups, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)
     try? frcGroup?.performFetch()

     if let members = frcGroup?.fetchedObjects?.first?.members {
            for member in members{
                  print("member.status \(member.status)")
                }
             }
         }

我得到以下日志：

compoundPredicate status == 1 AND ANY members.status == 1
member.status 0
member.status 1
member.status 0

我也试了下面的，得到了和上面一样的日志：

let statusMemberPredicate = NSPredicate(format: "members.status CONTAINS %d", 1)

看起来它正在获取所有 members 并忽略 members.status == 1 谓词。

我做错了什么？

Answer 1

谓词仅确定正在获取的对象是否应包含在结果中。它对相关对象没有影响。在您的情况下，如果 Group 具有 status = 1，并且其任何相关 Member 对象具有 status = 1，则它将包含在结果中。但其 members 属性不受谓词影响。它将包括所有相关成员，即使它们与谓词不匹配。所以你的结果是我所期望的。

如果要过滤 members，您应该在获取组对象后单独进行。

核心数据：忽略对多谓词

Core Data: To-many predicate ignored

core-data

nsfetchedresultscontroller

nsfetchrequest

swift