核心数据无法识别选择器错误

Question

我正在使用Core Data来保存一些字符串.我有以下类名为Results

Results.h

#import <CoreData/CoreData.h>

@interface Results : NSManagedObject

@property(nonatomic, retain) NSString *lessondate;
@property(nonatomic, retain) NSString *lesson;
@property(nonatomic, retain) NSString *location;
@property(nonatomic, retain) NSString *start;
@property(nonatomic, retain) NSString *end;

@end

Results.m

#import "Results.h"

@implementation Results

@dynamic lessondate;
@dynamic lesson;
@dynamic location;
@dynamic start;
@dynamic end;

@end

以下是我执行保存的代码:

-(void)saveLesson{

Results *result = (Results *)[NSEntityDescription insertNewObjectForEntityForName:@"Diary" inManagedObjectContext:managedObjectContext];

result.lessondate = calendarDateString;
result.lesson = [NSString stringWithFormat:@"%@", lessonText.text];
result.location = [NSString stringWithFormat:@"%@", locationTest.text];
result.start = [NSString stringWithFormat:@"%@", startTimeText.text];
result.end = [NSString stringWithFormat:@"%@", endTimeText.text];
NSError *error;


// here's where the actual save happens, and if it doesn't we print something out to the console
if (![managedObjectContext save:&error])
{
    NSLog(@"Problem saving: %@", [error localizedDescription]);
}


[self dismissViewControllerAnimated:YES completion:nil];

}

但是当我尝试在应用程序中保存数据时,应用程序崩溃并显示这些错误

2013-02-18 11:46:25.705 After managedObjectContext: <NSManagedObjectContext: 0x1f892480>

2013-02-18 11:46:33.762 -[NSManagedObject setLesson:]: unrecognized selector sent to instance 0x1f80b380

2013-02-18 11:46:33.764  *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSManagedObject setLesson:]: unrecognized selector sent to instance 0x1f80b380'

有人可以告诉我为什么会崩溃吗？完全相同的代码在另一个应用程序中,并且工作正常.

Answer 1

您正在创建一个与您期望的实体不同的实体.

你在打电话

[NSEntityDescription insertNewObjectForEntityForName:@"Diary"
                              inManagedObjectContext:managedObjectContext];

这创造了实体Diary.将@"Results"作为方法的第一个参数.

当您将创建的Diary实体分配给Results对象时,它只是一个语法糖 - 下面的真实对象是您作为实体名称传递的内容. Diaryobject没有lesson属性,你得到了异常.