问题描述
- 访问一对一关系引发了崩溃
-
有两个表Assets和Rewards,对应关系是一对一。我想访问reward表。NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Assets"]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"assetsId == %@",str]; [request setPredicate:predicate]; [self.managedObjectContext executeFetchRequest:request onSuccess:^(NSArray *assetsArr) { for (Assets *assets in assetsArr) { NSLog(@"assets %@",[assets valueForKey:@"assetrewards.rewardsId"]); } } onFailure:^(NSError *error) { NSLog(@"Error fetching: %@", error); }];
崩溃报告:
: Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<Assets 0x9fb9380> valueForUndefinedKey:]: the entity Assets is not key value coding-compliant for the key "assetrewards.rewardsId".'
检测:
NSLog(@"assets %@",[assets valueForKey:@"assetrewards"]);
得到的输出结果:
assets <Rewards: 0xad8a4f0> (entity: Rewards; id: 0x9fe4bf0 <x-coredata://B2D33481-2AF2-4C6D-9428-33BDCF653881-15578-00004A2B32ACC29E/Rewards/pc05848de529d4cbab6eb4475a5f9f591> ; data: <fault>)
我想要通过对应关系访问reward内的所有值,或者是一个特定的asset可以得到对应reward的详细内容。
请高手指点。
解决方案
你不能使用valueForKey:
,在多步骤的路径,比如assetrewards.rewardsId
,需要使用valueForKeyPath:
。代码在寻找名为assetrewards.rewardsId的关键字,而不是名为assetrewards可以指向rewardsId对象的关键字
时间: 2024-08-02 00:15:22