ios - 'NSInvalidArgumentException'，原因 : 'keypath Patient.nachname not found in entity '

Question

为什么我会收到 NSInvalidArgumentException？

我的 TableView Controller 代码:

- (NSFetchedResultsController *)fetchedResultsController {

CoreDataHelper *cdh = [(MRMedSafeAppDelegate *) [[UIApplication sharedApplication] delegate] cdh];

if (_fetchedResultsController != nil) {
    return _fetchedResultsController;
}

NSFetchRequest  *fetchRequest = [[NSFetchRequest  alloc] init];
NSEntityDescription  *entity = [NSEntityDescription
                                entityForName:@"Patient" inManagedObjectContext:cdh.context];
[fetchRequest setEntity:entity];

NSSortDescriptor  *sort1 = [[NSSortDescriptor  alloc]
                            initWithKey:@"Patient.nachname" ascending:YES];
NSSortDescriptor  *sort2 = [[NSSortDescriptor  alloc]
                            initWithKey:@"Patient.vorname" ascending:YES];

[fetchRequest setSortDescriptors:[NSArray  arrayWithObjects:sort1, sort2, nil]];

[fetchRequest setFetchBatchSize:20];

NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                    managedObjectContext:cdh.context
                                      sectionNameKeyPath:nil
                                               cacheName:nil];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;

return _fetchedResultsController;

我的病人.h:

@interface Patient : NSManagedObject
@property (nonatomic, retain) NSDate * geburtsdatum;
@property (nonatomic, retain) NSString * nachname;
@property (nonatomic, retain) NSString * vorname;
@property (nonatomic, retain) NSNumber * weiblich;
@end

我的病人.m:

#import "Patient.h"
@implementation Patient
@dynamic geburtsdatum;
@dynamic nachname;
@dynamic vorname;
@dynamic weiblich;
@end

由 XCode 5 从 Model.xcdatamodeld 文件中生成的 Patient.h 和 Patient.h。

为什么我得到异常？

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'keypath Patient.nachname not found in entity '

患者是唯一的类，没有其他模型类，模型中也没有关系。

Answer 1

只需在

中使用“nachname”而不是“Patient.nachname”

NSSortDescriptor  *sort1 = [[NSSortDescriptor  alloc]
                        initWithKey:@"Patient.nachname" ascending:YES];

即应该是

NSSortDescriptor  *sort1 = [[NSSortDescriptor  alloc]
                        initWithKey:@"nachname" ascending:YES];

下一个排序描述符和“vorname”也是如此。