ios - 使用 NSURLSessionDataTask 链式请求

Question

我要使用 NSURLSessionDataTask 执行请求链。当第一个请求完成时，我需要使用第一个请求中的 responseData 来执行另一个多重请求。最后，我得到 NSArray 并提供给 TableView 。怎么做？如下所示，它不起作用。

NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:config];
NSString *tvdbId = [[NSUserDefaults standardUserDefaults] objectForKey:@"tvdbId"];
NSURL *urlString = [NSURL URLWithString:[NSString stringWithFormat:@"http://api.trakt.tv/show/seasons.json/%@/%@", kApiKey, tvdbId]];
__weak EpisodeViewController *weakSelf = self;
NSURLSessionDataTask *task = [manager dataTaskWithRequest:[NSURLRequest requestWithURL:urlString] completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
    if (!error) {
        NSArray *seasons = (NSArray *)responseObject;
        __block NSMutableArray *seasonArray = [NSMutableArray new];

        [seasons enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            NSString *seasonNumber = obj[@"season"]; 
            NSURL *urlString = [NSURL URLWithString:[NSString stringWithFormat:@"http://api.trakt.tv/show/season.json/%@/%@/%@", kApiKey, tvdbId, seasonNumber]];
            NSURLSessionDataTask *eposideTask = [manager dataTaskWithRequest:[NSURLRequest requestWithURL:urlString] completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
                NSArray *eposides = (NSArray *)responseObject;
                NSDictionary *dict = @{@"season": seasonNumber, @"eposodes": eposides};
                [seasonArray addObject:dict];
            }];
            [eposideTask resume];
        }];
        weakSelf.eposides = [NSArray arrayWithArray:seasonArray];
        NSLog(@"%@", weakSelf.eposides);

    }
}];
[task resume];

Answer 1

您可以使用 AFNetworking如果您正在下载数据

将您的操作(在您的情况下为 NSURLSessionDataTask)添加到 NSOperationQueue 中并将 maximumconcurrentoperationCount 设置为 1

从每个操作的Completion回调中获取下载的数据(操作结果)

示例代码

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *path = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"temp.zip"]];

    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:TempUrl]];
    operation = [[AFDownloadRequestOperation alloc] initWithRequest:request targetPath:path shouldResume:YES];

    operation.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];

    [operation setProgressiveDownloadProgressBlock:^(AFDownloadRequestOperation *operation, NSInteger bytesRead, long long totalBytesRead, long long totalBytesExpected, long long totalBytesReadForFile, long long totalBytesExpectedToReadForFile) {

         /// Check Download Progress        
        }
    }];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

     //// Success code goes here

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        NSLog(@"Error: %@", error);   

    }];

    [[self downloadQueue] addOperation:operation];