错误而用于添加场景的视图控制器的dealloc的NSManagedObjectContext，但确定为编辑场景

问题描述：

我已经两个控制器，一个被NSFetchedResultsController错误而用于添加场景的视图控制器的dealloc的NSManagedObjectContext，但确定为编辑场景

@interface AddressesController : UITableViewController<ManageAddressDelegate> 
@property(nonatomic, strong) NSFetchedResultsController *fetchedResultsController; 
@end

哪个显示地址通常称作AddressesController，并执行SegueAddAddress为用户动作如：

- (IBAction)addButtonClicked:(id)sender { 
    [self performSegueWithIdentifier:SegueNewAddress sender:sender]; 
}

，并执行SegueEditAddress当单击某行：

- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath { 
    Address *address = [self.fetchedResultsController objectAtIndexPath:indexPath]; 
    [self performSegueWithIdentifier:SegueEditAddress sender:address]; 
}

另一个控制器EditAddressController，它的两个SegueAddAddress和SegueEditAddress的destinationViewController：

@interface EditAddressController : UITableViewController<EZFormDelegate> 
@property (strong, nonatomic) Address *address; 
@property (strong, nonatomic) NSManagedObjectContext *context; 
@property (weak, nonatomic) id <ManageAddressDelegate> delegate; 
@end

我将与子的NSManagedObjectContext命名为编辑上下文中AddressesController＃prepareForSegue的地址准备子控制器SEGUE：发件人（设置代表协议也）

if ([segue.identifier isEqualToString:SegueEditAddress]) { 
    EditAddressController *controller = segue.destinationViewController; 
    controller.delegate = self; 
    NSManagedObjectContext *editContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType]; 
    editContext.MR_workingName = @"Edit Address Context"; 
    [editContext setParentContext:[self.fetchedResultsController managedObjectContext]]; 
    Address *address = sender; 
    Address *editAddress = [address inContext:editContext]; 
    controller.address = editAddress; 
    controller.context = editContext; 
}

为还加入准备在addingContext一个新地址：

if ([segue.identifier isEqualToString:SegueNewAddress]) { 
    EditAddressController *controller = segue.destinationViewController; 
    controller.delegate = self; 
    NSManagedObjectContext *addingContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType]; 
    addingContext.MR_workingName = @"Adding Address Context"; 
    [addingContext setParentContext:[self.fetchedResultsController managedObjectContext]]; 
    Address *newAddress = [Address createInContext:addingContext]; 
    controller.address = newAddress; 
    controller.context = addingContext; 
}

当用户单击保存EditAddressController按钮，它会回调委托（AddressesController）与下面的代码后，填写地址属性：

- (IBAction)save:(id)sender { 
    [self.delegate controller:self save:self.address]; 
}

和原点AddressesController将由相同的处理新的或编辑行动回调函数：

- (void)controller:(EditAddressController *)controller save:(Address *)address { 
    NSArray *keys = @[@"username", @"phone", @"zipcode", @"street"]; 
    NSDictionary *attributes = [address dictionaryWithValuesForKeys:keys]; 
    void (^success)(AFHTTPRequestOperation *, id) = ^(AFHTTPRequestOperation *operation, id responseObject) { 
     [address importValuesForKeysWithObject:[responseObject JSONValue]]; 
     [address.managedObjectContext saveToPersistentStoreAndWait]; 
     [self.navigationController popViewControllerAnimated:YES]; 
    }; 
    void (^failure)(AFHTTPRequestOperation *, NSError *) = ^(AFHTTPRequestOperation *operation, NSError *error) { 
     DDLogError(@"Failed to create address because of: %@", error); 
    }; 

    if (address.id == nil || address.id.intValue == 0) { 
     [self.http postPath:@"addresses" parameters:parameters success:success failure:failure]; 
    } else { 
     NSString *path = [NSString stringWithFormat:@"addresses/%@", address.id]; 
     [self.http putPath:path parameters:parameters success:success failure:failure]; 
    } 
}

该函数只是将新的或编辑的地址发布到服务器，并在http确定后将其保存到CoreData中。我使用魔法记录来执行CoreData相关操作和上述代码[address.managedObjectContext saveToPersistentStoreAndWait];”意愿引起默认上下文中也被保存和我曾尝试使用正常[的NSManagedObjectContext：保存：错误]中，错误是一样的

问题是，虽然添加和编辑逻辑是相同的99％，但它可以编辑。当我添加一个地址，它将被保存到数据库，并引发一个异常当[self。navigationController popViewControllerAnimated：YES]被调用时，发生错误时EditAddressController的dealloc所述的ivar 上下文：

EXC_BAD_ACCESS（代码= 2，地址= 0x3）

错误堆栈带有（列出一些关键功能只）：

[NSPersistStoreCache decrementRefCountForObjectID] 
... 
[NSManagedObjectContext(_NestedContextSupport) managedContextDidUnregisterObjectsWithIDs:] 
... 
[NSManagedObjectContext dealloc]

经过一些测试后，我发现两个案例之间最重要的区别是地址对象，新地址相关联的上下文似乎已经'绑定'并拒绝任何'release/dealloc'尝试。 – Kadvin 2013-04-23 06:11:02

答

经过几轮测试中，我找到了根本原因：

我们应该低于消息后发送一个复位消息给管理对象上下文：

[address.managedObjectContext saveToPersistentStoreAndWait]; 

[address.managedObjectContext reset];

而且我不知道为什么编辑对象不会造成错误的想法。

错误而用于添加场景的视图控制器的dealloc的NSManagedObjectContext，但确定为编辑场景

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