Ios 应用程序重启后核心数据为空

当我启动应用程序并通过

UITextField

向

Core data

输入一些数据时，它们会正确显示在

UITableView

中。问题是当我重新启动应用程序时，来自

核心数据的所有数据都会丢失。。。这是我的密码


@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;





创建卡车对象后，必须保存上下文，以便将其写入数据库

- (IBAction)saveButtonPressed:(id)sender {
    Truck *truck = [NSEntityDescription insertNewObjectForEntityForName:@"Truck" inManagedObjectContext:_managedObjectContext];
    [truck setModel:self.tField.text];
    [_managedObjectContext save:nil];  // you should provide an NSError object
}

- (IBAction)saveButtonPressed:(id)sender {
    Truck *truck = [NSEntityDescription insertNewObjectForEntityForName:@"Truck" inManagedObjectContext:_managedObjectContext];
    [truck setModel:self.tField.text];
}

- (IBAction)saveButtonPressed:(id)sender {
    Truck *truck = [NSEntityDescription insertNewObjectForEntityForName:@"Truck" inManagedObjectContext:_managedObjectContext];
    [truck setModel:self.tField.text];
    [_managedObjectContext save:nil];  // you should provide an NSError object
}