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伙计们，我正在从一个结构如下的 plist 中阅读：

财产清单

可以看到，它是一个plist，包含了不同类型（C，Visitor）的注解信息。我可以很好地显示每种注释类型，但我试图遍历所有类型并一次在地图视图上显示所有注释。这是代码：

NSLog(@"loadAnnotations");
NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"PermitData" ofType:@"plist"];
NSDictionary *rootOfPermitDataPlistDict = [[NSDictionary alloc] initWithContentsOfFile:plistPath];
// NSMutableDictionary *permitDict = [[NSMutableDictionary alloc] init];
 if ([self title] == @"All Permits") {
  for (id key in rootOfPermitDataPlistDict) {
   NSLog(@"key:%@",key);

   //[key retain];
   NSMutableDictionary *permitDict = [NSDictionary dictionaryWithDictionary:[rootOfPermitDataPlistDict objectForKey:key]];
   //[key release];

   //array containing annotation information: latitude, longitude, title, subtitle(see PermitData.plist)
   NSArray *annotationsArray = [[NSArray alloc] initWithArray:[permitDict objectForKey:@"annotations"]];
   [permitDict release];
   [rootOfPermitDataPlistDict release];

   CLLocationCoordinate2D workingCoordinate;
   NSDictionary *annotationContainerDict = [[NSDictionary alloc] init];
   //loop through annotations array, creating parking annotations filled with the information found in the plist
   for(annotationContainerDict in annotationsArray){
    NSLog(@"%@",annotationContainerDict);

    ParkingAnnotation *parkingAnnot = [[ParkingAnnotation alloc] init];
    workingCoordinate.latitude = [[annotationContainerDict objectForKey:@"latitude"] doubleValue];
    workingCoordinate.longitude = [[annotationContainerDict objectForKey:@"longitude"] doubleValue];
    [parkingAnnot setCoordinate:workingCoordinate];
    [parkingAnnot setTitle:[annotationContainerDict objectForKey:@"title"]];
    [parkingAnnot setSubtitle:[annotationContainerDict objectForKey:@"subtitle"]];
    if ([parkingAnnot title] == @"C Parking") [parkingAnnot setAnnotationType:annotationTypeC];
    else if ([parkingAnnot title] == @"Visitor Parking") [parkingAnnot setAnnotationType:annotationTypeVisitor];
    [mapView addAnnotation:parkingAnnot];
    [parkingAnnot release];
   }
   [permitDict release];
  }
 }

这是我运行程序时的控制台输出：

2010-11-25 03:25:28.020 Parking[38918:207] All Permits
2010-11-25 03:25:28.021 Parking[38918:207] loadAnnotations
2010-11-25 03:25:28.021 Parking[38918:207] key:C
2010-11-25 03:25:28.021 Parking[38918:207] {
    latitude = "38.545301";
    longitude = "-121.754066";
    subtitle = "VP 17";
    title = "C Parking";
}
2010-11-25 03:25:28.022 Parking[38918:207] {
    latitude = "38.544831";
    longitude = "-121.754785";
    subtitle = "VP 16";
    title = "C Parking";
}
2010-11-25 03:25:28.022 Parking[38918:207] {
    latitude = "38.544781";
    longitude = "-121.755729";
    subtitle = "VP 22";
    title = "C Parking";
}
2010-11-25 03:25:28.022 Parking[38918:207] {
    latitude = "38.544412";
    longitude = "-121.752489";
    subtitle = "VP 15";
    title = "C Parking";
}

所以它正确地循环通过第一个 NSDictionary，但是当它即将开始循环通过下一个时崩溃。而且我尝试将 NSDictionary 更改为 NSMutableDictionary 但结果是一样的。因此，当我在表格视图中选择“所有许可”行时，它会挂起几分之一秒（没有切换到地图视图），然后崩溃，而不会产生错误。

如果有人不介意在这里帮助我，我将不胜感激。提前致谢！

编辑：这是堆栈跟踪（在下面的评论中描述）：

2010-11-25 20:28:08.141 Parking[39400:207] All Permits
2010-11-25 20:28:08.142 Parking[39400:207] loadAnnotations
2010-11-25 20:28:08.142 Parking[39400:207] key:C
2010-11-25 20:28:08.143 Parking[39400:207] {
    latitude = "38.545301";
    longitude = "-121.754066";
    subtitle = "VP 17";
    title = "C Parking";
}
2010-11-25 20:28:08.143 Parking[39400:207] {
    latitude = "38.544831";
    longitude = "-121.754785";
    subtitle = "VP 16";
    title = "C Parking";
}
2010-11-25 20:28:08.143 Parking[39400:207] {
    latitude = "38.544781";
    longitude = "-121.755729";
    subtitle = "VP 22";
    title = "C Parking";
}
2010-11-25 20:28:08.144 Parking[39400:207] {
    latitude = "38.544412";
    longitude = "-121.752489";
    subtitle = "VP 15";
    title = "C Parking";
}
2010-11-25 20:28:08.145 Parking[39400:207] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSCFDictionary: 0x6d5fd80> was mutated while being enumerated.<CFBasicHash 0x6d5fd80 [0x2667380]>{type = mutable dict, count = 1,
entries =>
    0 : <0x7380> = <NSKeyValueContainerClass: Original class: ParkingAnnotation, Notifying class: NSKVONotifying_ParkingAnnotation>
}
'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x025fdb99 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x0274d40e objc_exception_throw + 47
    2   CoreFoundation                      0x025fd659 __NSFastEnumerationMutationHandler + 377
    3   Parking                             0x00002e93 -[ParkingMapViewController loadAnnotations] + 364
    4   Parking                             0x00002caf -[ParkingMapViewController viewDidLoad] + 117
    5   UIKit                               0x0036a5ca -[UIViewController view] + 179
    6   UIKit                               0x003689f4 -[UIViewController contentScrollView] + 42
    7   UIKit                               0x003787e2 -[UINavigationController _computeAndApplyScrollContentInsetDeltaForViewController:] + 48
    8   UIKit                               0x00376ea3 -[UINavigationController _layoutViewController:] + 43
    9   UIKit                               0x00378067 -[UINavigationController _startTransition:fromViewController:toViewController:] + 326
    10  UIKit                               0x00372ccd -[UINavigationController _startDeferredTransitionIfNeeded] + 266
    11  UIKit                               0x00379d8b -[UINavigationController pushViewController:transition:forceImmediate:] + 876
    12  UIKit                               0x00372b67 -[UINavigationController pushViewController:animated:] + 62
    13  Parking                             0x00002914 -[PermitListViewController tableView:didSelectRowAtIndexPath:] + 307
    14  UIKit                               0x00333a48 -[UITableView _selectRowAtIndexPath:animated:scrollPosition:notifyDelegate:] + 1140
    15  UIKit                               0x0032a32e -[UITableView _userSelectRowAtIndexPath:] + 219
    16  Foundation                          0x0003f21a __NSFireDelayedPerform + 441
    17  CoreFoundation                      0x025def73 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 19
    18  CoreFoundation                      0x025e05b4 __CFRunLoopDoTimer + 1364
    19  CoreFoundation                      0x0253cdd9 __CFRunLoopRun + 1817
    20  CoreFoundation                      0x0253c350 CFRunLoopRunSpecific + 208
    21  CoreFoundation                      0x0253c271 CFRunLoopRunInMode + 97
    22  GraphicsServices                    0x02edc00c GSEventRunModal + 217
    23  GraphicsServices                    0x02edc0d1 GSEventRun + 115
    24  UIKit                               0x002ceaf2 UIApplicationMain + 1160
    25  Parking                             0x00001e08 main + 102
    26  Parking                             0x00001d99 start + 53
)
terminate called after throwing an instance of 'NSException'

但是，我在 for 循环中释放了 permitDict（第二个 [permitDict release] 未注释），所以我不知道为什么它抱怨 NSDictionary 是不可变的。如您所见，permitDict 的类型为 NSMutableDictionary，所以我不知道为什么它会给我这个错误。

4

2 回答 2

4

代码崩溃有两个主要原因。

首先，在 for 循环内的这一行：

[rootOfPermitDataPlistDict release];

破坏您当前正在循环的对象。将它移到最后——在if ([self title]...语句的右大括号之后。

其次，这两行说：

[permitDict release];

应该被删除。不要释放 permitDict，因为您正在使用返回自动释放对象的 dictionaryWithDictionary 创建它。

通过这两个更改，代码应该可以运行。

但是，还有一些其他问题：

  • 你 alloc+initannotationsArray但从不释放它（内存泄漏）。在通过该数组的 for 循环之后释放它（您当前有第二个[permitDict release];）。
  • 您 alloc+initannotationContainerDict但随后仅将变量用作对 annotationsArray 中对象的引用（因此放弃了分配的内存 - 内存泄漏）。不要费心在 annotationContainerDict 上做 alloc+init，只需声明它。更改NSDictionary *annotationContainerDict = [[NSDictionary alloc] init];为NSDictionary *annotationContainerDict;.
  • 您正在使用 比较字符串==。像这样使用isEqualToString:：
    if ([[self title] isEqualToString:@"All Permits"]).... 有关为什么应该使用的解释isEqualToString，请参阅这个问题和这个问题。
  • 这里并不是一个真正严重的问题，但没有必要使用 dictionaryWithDictionary 并因此复制 rootOfPermitDataPlistDict 中已经存在的内容。您可以只使用 permitDict 作为对嵌入式字典的速记引用，如下所示NSMutableDictionary *permitDict = [rootOfPermitDataPlistDict objectForKey:key];：
  • 与 annotationsArray 相同：您不需要分配 + 初始化一个新数组。该数组已经在 rootOfPermitDataPlistDict 中。只需像这样引用它：NSArray *annotationsArray = [permitDict objectForKey:@"annotations"];. 如果您决定这样做，请不要释放 annotationsArray。

内存管理编程指南详细解释了所有这些。

于 2010-11-26T05:04:18.740 回答
1

首先，您的代码存在许多问题，但除非这是性能关键代码，否则您将每秒循环数百次（这可能会创建许多自动释放的对象），使用 alloc] init] 方法只会使代码更难跟随。（因为您必须在精神上经历并不断平衡分配与释放）。不要误会我的意思，了解保留和释放等很重要，但这是我解决问题的方式。

请记住，你在控制之中。让您的停车注释类能够“独立思考”一点。在下面的示例中，我添加了一个 -(id)initWithDictionary: 以便您的其他班级不必坐在那里完成所有繁琐的设置键的繁琐工作。（有一些虚构的部分我假设你会填写空白......

NSString * const PPAnnotationsKey   = @"annotations";
NSString * const PPTitleKey         = @"title";
NSString * const PPSubtitleKey      = @"subtitle";
NSString * const PPLatitudeKey      = @"latitude";
NSString * const PPLongitudeKey     = @"longitude";

NSLog(@"loadAnnotations");
NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"PermitData" ofType:@"plist"]; // autoreleased
NSDictionary *permitDictionary = [NSDictionary dictionaryWithContentsOfFile:plistPath]; // autoreleased
if ([[self title] isEqualToString:@"All Permits"]) {
    for (NSString *parkingGroup in permitDictionary) {
        NSLog(@"parkingGroup == %@", parkingGroup);
        NSArray *annotations = [parkingGroup objectForKey:PPAnnotationsKey];
        for (NSDictionary *entry in annotations) {
            PPParkingAnnotation *annotation = [PPParkingAnnotation parkingAnnotationWithDictionary:entry]; // autoreleased
            if (annotation) {
            // assuming here that mapView's addAnnotation: will retain the
            // annotation
            [mapView addAnnotation:annotation]; 
            }
        }
    }
}

@interface PPParkingAnnotation : NSObject <MKAnnotation> {
    CLLocationCoordinate2D   coordinate;
    NSString                *title;
    NSString                *subtitle;
}
+ (id)parkingAnnotationWithDictionary:(NSDictionary *)dictionary;
- (id)initWithDictionary:(NSDictionary *)dictionary;

@properties...
@end

@implementation PPParkingAnnotation

+ (id)parkingAnnotationWithDictionary:(NSDictionary *)dictionary {
    return [[[[self class] alloc] initWithDictionary:dictionary] autorelease];
}

- (id)initWithDictionary:(NSDictionary *)dictionary {
    [self setTitle:[dictionary objectForKey:PPTitleKey]];
    [self setSubtitle:[dictionary objectForKey:PPTitleKey]];
    // and so on.
}
于 2010-11-26T05:43:47.073 回答