小编Ani*_*nil的帖子

我从http://www.appcoda.com/introduction-to-core-data/了解了核心数据,但是当我自己开发一个示例项目时,很多错误出现在两个文件中.任何帮助将不胜感激,因为我是iPhone开发的新手

    //
//  PupilViewController.m
//  Pupils
//
//  Created by Lukasz Mozdzen on 21.04.2013.
//  Copyright (c) 2013 Lukasz Mozdzen. All rights reserved.
//

#import "PupilViewController.h"

@interface PupilViewController ()
@property (strong) NSMutableArray *pupils;

@end

@implementation PupilViewController


- (NSManagedObjectContext *)managedObjectContext
{
    NSManagedObjectContext *context = nil;
    id delegate = [[UIApplication sharedApplication] delegate];
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }
    return context;
}


- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    // Fetch the devices from persistent data store
    NSManagedObjectContext *managedObjectContext = …