将自定义NSOperations添加到NSOperationQueue时内存泄漏

Question

我正在分析（泄漏）我的应用程序（ARC），它显示了几个我无法弄清楚的内存泄漏。

一个对象（ArchivingTasksManager）启动一个在for循环中创建许多NSOperations的方法，并将它们添加到队列中。每个NSOperation都是一个自定义子类（DownloadImageOperation），我用NSURL实例化。

在ArchivingTasksManager中：

AccountId   Name    Active  Users   Forms
1           Child     T      3       4
5          Child2     F      4       3

在DownloadImageOperation中：

- (void)archiveAllImages
{    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self beginBackgroundTask];
        [self archiveImages];
    });
}

- (void)archiveImages
{
    self.queue.suspended = true;
    self.queue.maxConcurrentOperationCount = 1;

    for (Highlight *highlight in self.list.highlights) {
        for (Experience *experience in highlight.experiences) {
            for (NSURL *imageURL in [experience allImageURLsOfType:ExperienceImageType640x640]) {
                DownloadImageOperation *experienceImageDownload = [[DownloadImageOperation alloc] initWithImageURL:imageURL];

                [self.queue addOperation:experienceImageDownload];
            }

            NSURL *authorURL = [NSURL URLWithString:experience.author.image_250x250Url];

            if (authorURL) {
                DownloadImageOperation *authorImageDownload = [[DownloadImageOperation alloc] initWithImageURL:authorURL];

                [self.queue addOperation:authorImageDownload];
            }
        }

        MapSnapshotOperation *mapSnapshot = [[MapSnapshotOperation alloc] initWithHighlight:highlight];
        [self.queue addOperation:mapSnapshot];
    }

    [self.queue addObserver:self
                 forKeyPath:NSStringFromSelector(@selector(operationCount))
                    options:NSKeyValueObservingOptionInitial context:nil];

    self.totalOperations = self.queue.operationCount;
    self.queue.suspended = false;
}

以下是仪器在ArchivingTasksManager中显示的内容：

以下是Instruments在DownloadImageOperation中显示的内容：