iphone - 我们应该手动释放 NSDate 吗？

Question

我在头文件中使用以下配置声明了 NSDate:

# TestController.h
@interface TestController : UITableViewController{
    NSDate      *selectedDate;
    NSManagedObject *task;
}
    @property (nonatomic, retain) NSManagedObject *managedObject;
    @property (retain) NSDate *selectedDate 
@end

# TestController.m
@implementation TestController
    - (void)viewDidLoad {
        self.selectedDate = [managedObject valueForKey:@"title"];
    }
    - (void)viewDidUnload {
        self.task = nil;
        self.selectedDate = nil;
    }

    - (void)dealloc {
        [self.task release]
      [self.selectedDate release];
      [super dealloc];
    }
@end

根据我的理解，您应该释放分配、复制或保留的变量。由于我在这里保留变量数据，所以我在dealloc时释放。但是，最终抛出内存释放错误:

[NSDate isNSDate]:发送到释放实例 0x6923750 的消息”

如果我没有手动释放它，它工作正常。我的问题是我应该为这种情况释放变量吗？

更新:

用僵尸模板进行了仪器测试，这是输出:

#   Category    Event Type  RefCt   Timestamp   Address Size    Responsible Library Responsible Caller
0   __NSDate    Malloc  1   1331055104  0x895e9d0   16  CoreData    -[NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:]
1   __NSDate    Retain  2   1333056000  0x895e9d0   0   Task    -[TaskViewCell configureData:]
2   __NSDate    Retain  3   3045008128  0x895e9d0   0   CoreData    -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:]
3   __NSDate    Retain  4   3054921984  0x895e9d0   0   CoreData    -[NSSQLRow copy]
4   __NSDate    Release 3   3059244032  0x895e9d0   0   CoreData    -[NSSQLOperation dealloc]
5   __NSDate    Release 2   3059607040  0x895e9d0   0   CoreData    -[NSKnownKeysDictionary1 dealloc]
6   __NSDate    Retain  3   3715918848  0x895e9d0   0   CoreData    -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:]
7   __NSDate    Retain  4   3727657984  0x895e9d0   0   CoreData    -[NSSQLRow copy]
8   __NSDate    Release 3   3730131200  0x895e9d0   0   CoreData    -[NSSQLOperation dealloc]
9   __NSDate    Release 2   3730286080  0x895e9d0   0   CoreData    -[NSKnownKeysDictionary1 dealloc]
10  __NSDate    Retain  3   4250617856  0x895e9d0   0   CoreData    -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:]
11  __NSDate    Retain  4   4250759936  0x895e9d0   0   CoreData    -[NSManagedObject setValue:forKey:]
12  __NSDate    Release 3   4250761984  0x895e9d0   0   CoreData    -[NSManagedObject setValue:forKey:]
13  __NSDate    Retain  4   4260489984  0x895e9d0   0   CoreData    -[NSSQLRow copy]
14  __NSDate    Release 3   4263536896  0x895e9d0   0   CoreData    -[NSSQLOperation dealloc]
15  __NSDate    Release 2   4263687168  0x895e9d0   0   CoreData    -[NSKnownKeysDictionary1 dealloc]
16  __NSDate    Release 1   4656624128  0x895e9d0   0   Task    -[TaskEditController dealloc]
17  __NSDate    Retain  2   7570179840  0x895e9d0   0   CoreData    -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:]
18  __NSDate    Retain  3   7570360064  0x895e9d0   0   CoreData    -[NSManagedObject setValue:forKey:]
19  __NSDate    Release 2   7570361088  0x895e9d0   0   CoreData    -[NSManagedObject setValue:forKey:]
20  __NSDate    Retain  3   7577499136  0x895e9d0   0   CoreData    -[NSSQLRow copy]
21  __NSDate    Release 2   7602608128  0x895e9d0   0   CoreData    -[NSSQLOperation dealloc]
22  __NSDate    Release 1   7602752256  0x895e9d0   0   CoreData    -[NSKnownKeysDictionary1 dealloc]
23  __NSDate    Release 0   7971558144  0x895e9d0   0   Task    -[TaskEditController dealloc]
24  __NSDate    Zombie  -1  9697122048  0x895e9d0   0   Foundation  -[NSDateFormatter stringForObjectValue:]

没看懂什么意思。但是，我猜 coredata 是否会在保留的情况下发布 NSDate？

Answer 1

解决过度释放对象问题的最佳方法是启动 Instruments(在 XCode 中，键入 ⌘-I 而不是 ⌘-R)并选择“Zombies”模板——它会告诉你在哪里每个对象都被保留和释放，并在您的代码向已释放的实例发送消息时告诉您。

在这种情况下，不平衡的释放可能潜伏在您代码中的其他地方，而在您的 dealloc 方法中放置释放会暴露其他地方的问题。在任何情况下，对您问题的直接回答是“是的，您应该释放您保留的变量”，并且您在此处发布的代码具有正确的保留与发布比率(即一对一)，因此我会寻找您可能发布此 NSDate 的其他地方。