我有两个实体之间的一对多关系。运动员(评估)<-->>评估(whosEval)。我试图只显示被选中的运动员的评价。但是，当我尝试通过 eval.whosEval 访问关系时，出现未定义的错误。当我运行该应用程序时，该表是空的，而如果我注释掉谓词，它会显示所有运动员的所有评估。我错过了什么吗？谢谢。
allEvals.m
-(void)viewWillAppear:(BOOL)animated{
self.title = [NSString stringWithFormat:@"%@'s Evaluations",_athletesFullName];
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
_managedObjectContext = [appDelegate managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSFetchRequest *athleteRequest = [[NSFetchRequest alloc] init];
[athleteRequest setEntity:[NSEntityDescription entityForName:@"Athlete" inManagedObjectContext:_managedObjectContext]];
NSError *athleteError = nil;
NSArray *results = [_managedObjectContext executeFetchRequest:athleteRequest error:&athleteError];
NSPredicate *athletePredicate = [NSPredicate predicateWithFormat:@"full == %@", _athletesFullName];
[request setPredicate:athletePredicate];
Athlete *currentAthlete = [results objectAtIndex:0];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"whosEval == %@", currentAthlete];
[request setPredicate:predicate];
NSEntityDescription *eval = [NSEntityDescription entityForName:@"Eval" inManagedObjectContext:_managedObjectContext];
[request setEntity:eval];
NSSortDescriptor *sortDescriptor =
[[NSSortDescriptor alloc] initWithKey:@"date_recorded"
ascending:NO
selector:@selector(localizedCaseInsensitiveCompare:)];
NSArray *sortDescriptors = [[NSArray alloc]initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[_managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil){
//handle error
}
[self setEvalArray:mutableFetchResults];
[self.tableView reloadData];
NSLog(@"Athlete's Full Name is: %@",_athletesFullName);
}
最佳答案
你的谓词在它真正应该使用运动员对象时却使用了运动员姓名:
@"whosEval == %@", self.athlete
关于ios - NSPredicate 不会工作？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18293447/