小编ste*_*anr的帖子

我尝试扩展NSManagedObject.使用XCode我创建了MyBox.m和MyBox.h(直接来自xcdatamodel文件).

然后我修改了这些文件:

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>


@interface MyBox : NSManagedObject

@property (nonatomic, retain) NSDate * endDate;
@property (nonatomic, retain) NSNumber * globalId;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSDate * startDate;

-(NSString *)sayHello;

@end

和

#import "MyBox.h"
@implementation MyBox

@dynamic endDate;
@dynamic globalId;
@dynamic name;
@dynamic startDate;

-(NSString *)sayHello {
    return @"hello";
}  

@end

我可以获取所有myBoxes

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

NSMutableArray *myBoxes = [context executeFetchRequest:fetchRequest error:&error];

但后来我打来电话

MyBox …