ios - NSOperationQueue 中类的对象 - 使用委托(delegate)的异步方法

Question

我创建了一个 NSOperation 的子类，名为 DownloadQueue。我将所有对象一一添加到 NSOperationQueue，即 appDelegate.queueDownload。

问题是当 DownloadOperation 的对象被执行时，一旦 DownloadOperation 的 download 方法执行，我的 DownloadOperation 从队列中删除。

但我必须将它保存在内存中，因为当我在 DownloadOperation.m 中进行异步调用 [using downloadFromPath] 并且服务器响应文件数据时，当时DownloadOperation 对象被释放并且 liveOperationSucceeded 从未被调用。

可能是我觉得这个问题有点复杂，所以在标记它之前请先阅读它两遍!!这对我很重要。感谢理解。

    // Adding to queue

    DownloadOperation *operation = [[DownloadOperation alloc] init];

    operation.delegate = self;

    [operation operationWithFileOrFolderID:dictDocument[@"id"] withParentPath:self.strParentPath download:NO withFileName:dictDocument[@"name"] withDictionary:dictDocument];
    [operation download];

    [operation setQueuePriority:NSOperationQueuePriorityVeryHigh];

    [appDelegate.queueDownload addOperation:operation];

DownloadOperation.m (which is Subclass of NSOperation)

@implementation DownloadOperation

-(void)main
{
    [self download];
}

- (void)operationWithFileOrFolderID: (NSString *)strID withParentPath: (NSString *)strParentPath download: (BOOL)isDownload withFileName: (NSString *)strFileName withDictionary: (NSMutableDictionary *)dictInfoLocal
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    self.documentsDirectory = paths[0];

    self.strFileName = strFileName;
    self.strID = strID;
    self.strParentPath = strParentPath;
    self.dictInfo = dictInfoLocal;

    if (self)
    {

    }
}

- (void)download
{
    self.liveClient = [[LiveConnectClient alloc] initWithClientId:CLIENT_ID delegate:self];

    [self.liveClient downloadFromPath:[self.strID stringByAppendingString:@"/content"] delegate:self];

    NSLog(@"DownloadFilesVC : Downloading : %@",self.strFileName);    
}

- (void) liveOperationSucceeded:(LiveOperation *)operation
{

}

- (void) liveOperationFailed:(NSError *)error
                   operation:(LiveOperation *)operation
{

}

- (void) liveDownloadOperationProgressed:(LiveOperationProgress *)progress data:(NSData *)receivedData operation:(LiveDownloadOperation *)operation
{

}

@end

Answer 1

您在一个操作中有一个异步操作。

操作队列正在做它应该做的事情，并且在方法 download 完成后弹出完成的 DownloadOperation。它不关心操作是否有回调。

您需要保留 DownloadOperation 操作的所有权，方法是将它添加到强引用集合(例如 NSArray 或 NSSet)并在指定位置丢弃它LiveConnectClient 完成后的点。您可能希望在 DownloadOperation 中添加一个 BOOL 属性。

@property BOOL imReallyReallyFinishedAndCanBeDiscardedOK;

编辑

API 是基于异步/委托(delegate)的。一种简单的方法是遍历文件夹内容并计算返回响应。一旦您收到与请求数量相匹配的回复数量，您就知道您已经完成了。

作为一个非常简化的版本，不关心递归或错误。

@interface DownloadManager  : NSObject

@property NSArray *fileRefList;
@property NSUInteger count;
@property (strong) void (^completionBlock)();

@end

@implementation DownloadManager

-(void)downloadAllTheFiles {

    self.count = 0;
    for(NSString *strID in self.fileRefList) {

        LiveConnectClient *liveClient = [[LiveConnectClient alloc] initWithClientId:CLIENT_ID delegate:self];
        [liveClient downloadFromPath:[strID stringByAppendingString:@"/content"] delegate:self];

    }

}

- (void) liveOperationSucceeded:(LiveOperation *)operation
{
    self.count++;
    [self haveIFinished];
}

- (void) liveOperationFailed:(NSError *)error
                   operation:(LiveOperation *)operation
{
    self.count++;
    [self haveIFinished];
}

-(void)haveIFinished {

    if (self.count == self.fileRefList.count) {
        if (self.completionBlock) {
            self.completionBlock();
        }
    }

}

让 API 为您执行队列操作和后台操作。完成后触发任意 block 。