Question

我无法访问我的NSManagedObject的属性。我看到了这个对象，可以访问viewDidLoad中的属性，然后访问viewWillAppear中的其他方法，我仍然会看到此对象，但在调用属性后获取null。

@interface ListsViewController（）

@property (weak, nonatomic) IBOutlet UITableView *tableView;
@property (strong, nonatomic) NSArray *lists;

@end

@implementation ListsViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    NSManagedObjectContext *managedObjectContext = [[CoreDataController sharedInstance] newManagedObjectContext];
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"List"];
    NSError *error = nil;
    NSArray *result = [managedObjectContext executeFetchRequest:request error:&error];
    if (!result) {
        NSLog(@"Failure fetch: %@", error);
    } else {
        self.lists = result;
        NSLog(@"%@", self.lists);
        List *list = [self.lists firstObject];
        NSLog(@"%@", list.name);
    }

    self.tableView.delegate = self;
//    self.tableView.dataSource = self;
}

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

    NSLog(@"%@", self.lists);
    List *list = [self.lists firstObject];
    NSLog(@"%@", list.name);
}

控制台：

(
 "<List: 0x7fb5b9e6b7c0> (entity: List; id: 0xd000000000040000 <x-coredata://D831EA3F-2A96-4AA8-B9CF-BFFEB0B6D611/List/p1> ; data: <fault>)",
 "<List: 0x7fb5b9e53700> (entity: List; id: 0xd000000000080000 <x-coredata://D831EA3F-2A96-4AA8-B9CF-BFFEB0B6D611/List/p2> ; data: <fault>)"
 )
Underway
(
 "<List: 0x7fb5b9e6b7c0> (entity: List; id: 0xd000000000040000 <x-coredata://D831EA3F-2A96-4AA8-B9CF-BFFEB0B6D611/List/p1> ; data: <fault>)",
 "<List: 0x7fb5b9e53700> (entity: List; id: 0xd000000000080000 <x-coredata://D831EA3F-2A96-4AA8-B9CF-BFFEB0B6D611/List/p2> ; data: <fault>)"
 )
(null)

我做错了什么？

更新

我的错误是我没有持有managedObjectContext：

@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;

- (void)viewDidLoad {
    self.managedObjectContext = [[CoreDataController sharedInstance] newManagedObjectContext];
}

现在工作正常。

在viewDidLoad之后无法访问NSManagedObject的属性

0 个答案: