将MKannotation添加到mapview会导致EXC_BAD_ACCESS错误

Question

在使用正确的值更新Core数据后，我想将这些值添加到地图视图中。 这是我为此而编写的代码：

-(void)updateMapWithPredicate:(NSPredicate *)predicate
{
    int numberOfElementiOnMap = 0;
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.ActiviIndicator startAnimating];

        [self.mapView removeAnnotations:self.mapView.annotations];
    });
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Photo"];
    if (predicate) {
        request.predicate = [NSCompoundPredicate andPredicateWithSubpredicates:@[[NSPredicate predicateWithFormat:@"(latitude != nil) AND (longitude != nil)"]
                                                                                 ,predicate]];
    } else {
        request.predicate = [NSPredicate predicateWithFormat:@"(latitude != nil) AND (longitude != nil)"];
    }

    //Get all different coordinate from core data.
    [request setPropertiesToFetch:@[@"latitude", @"longitude"]];
    [request setReturnsDistinctResults:YES];
    [request setResultType:NSDictionaryResultType];
    // Execute the fetch
    NSError *error = nil;
    NSArray *photos = [self.context executeFetchRequest:request error:&error];
    for (NSDictionary *coordinateDic in photos) {
        NSPredicate *predicateToSend;
        if (predicate) {
            /* Get all pictures that corresponding to the coordinate inside the coordinateDic
             */
            predicateToSend = [NSCompoundPredicate andPredicateWithSubpredicates:@[[NSPredicate predicateWithFormat:@"(latitude == %@) AND (longitude == %@)",
                                                                                    [coordinateDic valueForKey:@"latitude"], [coordinateDic valueForKey:@"longitude"]],predicate]];
        } else {
            predicateToSend = [NSPredicate predicateWithFormat:@"(latitude == %@) AND (longitude == %@)",[coordinateDic valueForKey:@"latitude"], [coordinateDic valueForKey:@"longitude"]];
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            //get all picture with the same lautide and longitude that are specified on predicate
            NSArray *photos2 = [Photo pictureFromContext:self.context withPredicate:predicateToSend];
            //if the pictures are more then one, we add only one picture, and we write the number of pictures as a subtitle of the mkannotationview
            if ([photos2 count] > 1) {
                Photo *photo = [photos2 lastObject];
                photo.photoDescription = [NSString stringWithFormat:@"album with %lu picures",(unsigned long)[photos2 count]];
                if (photo) {
                  //  [self.mapView addAnnotation:photo];
                }                
            } else { //add the only pictures
                if ([photos2 firstObject]) {
                   [self.mapView addAnnotation:[photos2 firstObject]];
                }
            }
        });
    }
}

在这段代码中，我基本上从核心日期中检索需要的值，然后将其添加到地图中。

我添加到地图中的对象显然符合<MKAnnotation>协议。我在[self.mapView addAnnotation:[photos2 firstObject]];行上收到错误。奇怪的是，我从核心日期获得的某些对象被正确添加到地图中。我尝试通过启用NSZombie来调试代码，但我得到了同样的错误。我也检查坐标和它的一切。我在调试代码时发现的唯一区别是： 正确添加到地图的对象在调试器中如下所示：

相反，当我收到错误时，我添加到地图的对象在模拟器上看起来像这样：

当我打印的内容为：0我得到这个：

Printing description of *([0]->[0]):
(Photo_Photo_) [0] = {}

它看起来像是指向空实体的指针。 你知道我怎么解决这个问题吗？ 感谢

Answer 1

提交错误报告后，Apple告诉我解决问题的方法。问题是我正在以非KVO兼容的方式更新坐标。我存储像你这样的属性，纬度和经度。尝试在Photo类上添加它。

- (void)willChangeValueForKey:(NSString *)key
{
    if ([key isEqualToString:@"latitude"] || [key isEqualToString:@"longitude"]) { [self willChangeValueForKey:@"coordinate"]; }
    [super willChangeValueForKey:key];
}

- (void)didChangeValueForKey:(NSString *)key
{
    if ([key isEqualToString:@"latitude"] || [key isEqualToString:@"longitude"]) { [self didChangeValueForKey:@"coordinate"]; }
    [super didChangeValueForKey:key];
}

希望这有帮助。