Objc-C：RACObserve 快速变化的值（AFHTTPRequestOperation 的 RACSignal）

Question

我正在使用反应式 cocoa 从服务器创建下载文件。我有一个 DownloadMapFileOperation.m 文件，进度为属性（进度值、currentBytes、totalBytes）。它在我的下一个 RACSignal 方法和浮动进度中变化非常快（这是不必要的，但是

@property (nonatomic, strong, readwrite) NSMutableDictionary *progressDictionary;
@property (nonatomic, assign, readwrite) float progress;

和RACSignal创建方法

- (RACSignal *)signalForDownloadMap:(Place *)place
{
    return [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSString *mapUrlString = [NSString stringWithFormat:@"http://myurl/%@", place.mapFileName];
        NSURL *url = [NSURL URLWithString:mapUrlString];
        NSURLRequest *request = [NSURLRequest requestWithURL:url];

        _downloadFileOperation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

        NSString *documentsDirectory = [paths objectAtIndex:0];

        NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[url lastPathComponent]];

        [_downloadFileOperation setOutputStream:[NSOutputStream outputStreamToFileAtPath:fullPath append:NO]];

        [_downloadFileOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation , id response)
         {
             NSLog(@"Downloaded via compl block");
             [subscriber sendNext:nil];
             [subscriber sendCompleted];

         } failure:^(AFHTTPRequestOperation *operation, NSError *error)
         {
             [subscriber sendError:error];
         }];

        @weakify(self)
        self.progressDictionary = [[NSMutableDictionary alloc] init];
        self.progressDictionary[@"progress"] = @(0);
        self.progressDictionary[@"current"] = @(0);
        self.progressDictionary[@"total"] = @(0);
        self.progress = @(0);

        [_downloadFileOperation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead)
         {
             @strongify(self)
             self.progressDictionary[@"current"] = @(totalBytesRead);
             self.progressDictionary[@"total"] = @(totalBytesExpectedToRead);
             self.progressDictionary[@"progress"] = @((float)totalBytesRead / (float)totalBytesExpectedToRead);
             self.progress = @((float)totalBytesRead / (float)totalBytesExpectedToRead);
             self.progress = @((float)totalBytesRead / (float)totalBytesExpectedToRead);
         }];

        [_downloadFileOperation start];
        return nil;
    }] filter:^BOOL(id value) {
        return !(.mapFileName == nil);
    }]
        deliverOn:[RACScheduler mainThreadScheduler]
    ];
}

我只是想通过 RACObserve 在我的 ViewController 中显示我的进度。

[[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place]
     subscribeNext:^(AFHTTPRequestOperation *operation) {
        NSString *alertMessage = @"Download complete";
        [[[UIAlertView alloc] initWithTitle:@"Complete" message:alertMessage delegate:self cancelButtonTitle:@"Close" otherButtonTitles: nil] show];
        downloadMapView.progressLabel.text = @"Download Complete";
    }];

    [[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place] subscribeError:^(NSError *error) {
        [[[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil] show];
    }];

    RAC(downloadMapView, progressView.progress) = [RACObserve([DownloadMapFileOperation sharedInstance], progress)
                                                   map:^id(id value) {
                                                       return value;
                                                   }];

  RAC(downloadMapView, progressLabel.text) = [RACObserve([DownloadMapFileOperation sharedInstance], progressDictionary)
                                                    map:^id(NSDictionary *value) {
                                                        return [value[@"progress"] isEqual: @(1)] ? @"Download Complete" : [NSString stringWithFormat:@"Downloaded %@ of %@", value[@"current"], value[@"total"]];
                                                    }];

但我的进度视图有时会从 60% 跳到 50%（或 45 - 35 等），并且 NSLog(@"Downloaded via compl block"); 在进度达到 100% 之前显示（有时达到并从大约 70% 开始）。如果我使用 progressDictionary（就像第二个 RACObserve）- 它不起作用（显示 0 进度和下载 0，共 0）

已编辑

我也尝试在我的 DownloadMapFileOperation.m 文件中添加暂停、恢复、取消下载操作的方法。

- (RACSignal *)signalForPauseDownloadMap
{
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [_downloadFileOperation pause];
        [subscriber sendNext:nil];
        [subscriber sendCompleted];
        return nil;
    }];
}

- (RACSignal *)signalForResumeDownloadMap
{
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [_downloadFileOperation resume];
        [subscriber sendNext:nil];
        [subscriber sendCompleted];
        return nil;
    }];
}

- (RACSignal *)signalForCancelDownloadMap
{
    return [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [_downloadFileOperation cancel];
        [subscriber sendNext:nil];
        [subscriber sendCompleted];
        return nil;
    }] filter:^BOOL(id value) {
        return (_downloadFileOperation);
    }];
}

但是：我的下载文件操作没有停止。当我在 VC

中使用时

[[_downloadMapFileOperation signalForPauseDownloadMap]
    subscribeNext:^(id x) {
        [downloadMapView setTitleForStartDownloadButton:@"Resume download"];
        _currentDownloadState = kHTDownloadStatePaused;
    }];

我的进度值工作正常（不会从一个值跳到另一个值）。请帮帮我。谢谢。

Answer 1

对于您关于跳跃下载进度的原始问题，问题是您正在创建对信号的两个副本的订阅，这导致了两次下载。即，这段代码：

[[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place]
 subscribeNext:^(AFHTTPRequestOperation *operation) {
    NSString *alertMessage = @"Download complete";
    [[[UIAlertView alloc] initWithTitle:@"Complete" message:alertMessage delegate:self cancelButtonTitle:@"Close" otherButtonTitles: nil] show];
    downloadMapView.progressLabel.text = @"Download Complete";
}];

[[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place] subscribeError:^(NSError *error) {
    [[[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil] show];
}];

每个 subscribeNext/subscribeError/等等。将创建一个新的订阅，并开始下载。您要订阅的内容如下：

[[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place]
 subscribeNext:^(AFHTTPRequestOperation *operation) {
    NSString *alertMessage = @"Download complete";
    [[[UIAlertView alloc] initWithTitle:@"Complete" message:alertMessage delegate:self cancelButtonTitle:@"Close" otherButtonTitles: nil] show];
    downloadMapView.progressLabel.text = @"Download Complete";
} error:^(NSError *error) {
    [[[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil] show];
}];

对于暂停和恢复，我认为创建更多信号没有意义。如果你确实有权访问下载文件操作，那么直接调用pause/resume就可以了。原始订阅将继续有效，并且应该 pause/resume 根据创建的信号内的行为进行更新。

至于取消，你真正想做的是使用一次性用品。在[RACSignal createSignal:]调用中，你不想returnnil。相反，设置一个一次性用品，在一次性用品被处理后取消下载。

编辑:

理想情况下，您希望通过信号发送进度。在 setDownloadProgressBlock 你会改为：

NSMutableDictionary *progressDictionary = [[NSMutableDictionary alloc] init];
progressDictionary[@"current"] = @(totalBytesRead);
progressDictionary[@"total"] = @(totalBytesExpectedToRead);
progressDictionary[@"progress"] = @((float)totalBytesRead / (float)totalBytesExpectedToRead);
[subscriber sendNext:[progressDictionary copy]];

然后您可以在订阅时阅读 progressDictionary，如下所示：

[[[DownloadMapFileOperation sharedInstance] signalForDownloadMap:self.place]
subscribeNext:^(NSDictionary *progressDictionary) {
    // Do stuff with dictionary here, like update UI with progress
} error:^(NSError *error) {
    // Error related stuff
} completed:^{
    // Completed stuff
}];

注意：如果没有充分的理由，您不应该通过 sendNext 发送 nil。完成逻辑应该只在完成块中完成。

Objc-C：RACObserve 快速变化的值（AFHTTPRequestOperation 的 RACSignal）

Objc-C: RACObserve rapidly changing values (RACSignal for AFHTTPRequestOperation)

ios

objective-c

reactive-cocoa

afhttprequestoperation