Question

我正在尝试为NSPredicate中使用的NSFetchResultsController创建一个UITableView。我有3个实体，User（1到多个） - ＆gt; Visit（1对多） - ＆gt; Treatment，并希望获得用户拥有的所有治疗方法。

我尝试过使用子查询SELF，ANY，只返回Visits而不是Treatments。

有人可以指导我如何从用户实体访问治疗实体吗？

提前感谢您的帮助！

Image of the CoreData Model

修改

这是我目前用来尝试获取处理的代码

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:kTreatmentVisits];
fetchRequest.sortDescriptors = descriptors;
fetchRequest.fetchBatchSize = 10;
fetchRequest.predicate = [NSPredicate predicateWithFormat:@"ANY treatmentVisits = %@.visitTreatment", user.userVisit];

结果我得到了访问，而不是治疗

<NSFetchRequest: 0x60b000148a40> (entity: treatmentVisits; predicate: (ANY treatmentVisits == {<Visits: 0x60b0000a0ad0> (entity: VisitsEntity; id: 0xd0000000000c000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p3> ; data: {
visitCause = "";
visitEndDate = nil;
visitId = nil;
visitRecommendation = "";
visitStartDate = "2016-08-11 04:43:50 +0000";
visitTreatment = "<relationship fault: 0x60300025e6d0 'visitTreatment'>";
visitType = 0;
visitUser = "0xd000000001940000 <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/UsersEntity/p101>";
}), <Visits: 0x60b0000bec10> (entity: VisitsEntity; id: 0xd00000000008000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p2> ; data: {
visitCause = "";
visitEndDate = nil;
visitId = nil;
visitRecommendation = "";
visitStartDate = "2016-08-04 20:26:33 +0000";
visitTreatment = "<relationship fault: 0x60300025e850 'visitTreatment'>";
visitType = 0;
visitUser = "0xd000000001940000 <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/UsersEntity/p101>";
}), <Visits: 0x60b000148570> (entity: VisitsEntity; id: 0xd00000000010000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p4> ; data: <fault>), <Visits: 0x60b000148620> (entity: VisitsEntity; id: 0xd00000000004000a <x-coredata://5CDB188C-2177-415B-9B74-E30B20EA4DAA/VisitsEntity/p1> ; data: <fault>)}.visitTreatment); sortDescriptors: ((
"(treatmentStartTime, descending, compare:)"
)); batch size: 10; type: NSManagedObjectResultType; )

我希望能够访问 visitTreatment

中的内容

我也试过

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"SELF IN %@", user.userVisit];

具有相同的结果。

Answer 1

首先，如果您想获得治疗，FRC的基础提取必须指定治疗实体：

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"TreatmentsEntity"];

然后通过指定谓词将结果限制为给定UsersEntity的处理，例如requiredUser：

fetchRequest.predicate = [NSPredicate predicateWithFormat:"treatmentVisits.visitUser == %@", requiredUser];

然后，您需要直接执行获取请求：

NSError *error = nil;
NSArray *results = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (results == nil) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();    
} else {
    NSLog(@"Results is %@",results);
}

或者，对于获取的结果控制器，使用fetchRequest初始化FRC，然后调用performFetch：

NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
NSError *error = nil;
if (![frc performFetch:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
} else {
    NSLog(@"Results %@",frc.fetchedObjects);
}

Answer 2

您需要使用Treatment作为要获取的实体。直到用户的参考两个级别应该是微不足道的，因为反向关系是一个。

正确的谓词就像是

NSPredicate(format: "visit.user = $@", user)

您的日志表明您正在访问，而非治疗。

NSPredicate用于NSFetchResultsController

2 个答案: