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我在异步进行ftp请求时遇到了一个问题，我尝试清楚地描述确切的问题：

- (void)viewDidLoad
{
    [super viewDidLoad];

    //I want to do a ftpListRequst in the background here
    dispatch_async(dispatch_get_global_queue(0, 0), ^{

        NewFTPListService *nfl = [[NewFTPListService alloc] initWithFtpPath:@"ftp://root:@10.0.0.3/"];

        [nfl listDirectoryContents];

        [nfl release];

    }); 

    //other main thread code
}

- (NSArray *) listDirectoryContents
{   
    [_listDir start];

    //What I want to do here is to wait until the ftp request finish
    while (!self.isFinish) {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    }

    NSLog(@"Request Finish!");

    return self.result;
}

-(void) start {
    ......
    self.streamInfo->readStream.delegate = self;
    [self.streamInfo->readStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [self.streamInfo->readStream open];

    //If request is blocked (may be the server is not avaliable), after a specific time, this block will be called
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kWRDefaultTimeout * NSEC_PER_SEC), dispatch_get_current_queue(), ^{       
        [self.delegate requestFailed:self];
        [self destroy];
    });

}

当请求成功时，会调用这个方法：

-(void) requestCompleted:(WRRequest *) request{

    self.isSucess = YES;
    self.isFinish = YES;
}

此方法将在“dispatch_after”块中调用

-(void) requestFailed:(WRRequest *) request{
    self.isSucess = NO;
    self.isFinish = YES; 
}

当请求成功时，我看到打印“请求完成！”。当请求被阻止并调用“dispatch_after”块时，会调用“requestFailed”方法，但我没有看到打印“请求完成！”。似乎程序以某种方式卡在了while循环中（循环没有运行，之后的代码也没有运行）。

更重要的是，如果我同步运行程序：

- (void)viewDidLoad
    {
        [super viewDidLoad];

        NewFTPListService *nfl = [[NewFTPListService alloc] initWithFtpPath:@"ftp://root:@10.0.0.3/"];

        [nfl listDirectoryContents];

        [nfl release];
    }

即使请求失败，我也可以成功看到打印“请求完成！”。我想知道为什么会发生这种情况以及如何解决这个问题，以便在请求失败时可以成功运行程序。谢谢！

4

1 回答 1

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嗨只需通过 performSelector 调用此方法

[nfl listDirectoryContents];

或者在 viewDidAppear 方法中调用这个方法。

于 2012-06-16T06:13:43.803 回答