如何檢查connectionDidFinishLoading何時完成

我在iOS應用程序中設置了一個簡單的Objective-C類，它有一個簡單的任務，下載一個JSON文件，解析它，然後傳回一個NSString，其中包含一個從下載的JSON文件。如何檢查connectionDidFinishLoading何時完成

我的問題是，我從另一個類調用這個類，這一切都很好，但是我需要將NSString傳回給我從中調用它的類。

的問題是，該方法傳回空的NSString BEFORE connectionDidFinishLoading發生....等等NSString的從未被分配一個字符串......

我已經建立了while循環在我的方法但它並沒有真正的工作.....

這裏是我的代碼：

-(NSString *)get_user_icon:(NSString *)YT_ID { 

// Set BOOL to 0 for initial setup. 
icon_check = 0; 

NSString *url_YT = [NSString stringWithFormat:YOUT_profile_part_2, YT_ID]; 

dispatch_queue_t downloadQueue = dispatch_queue_create("Icon downloader YouTube", NULL); 
dispatch_async(downloadQueue, ^{ 

    dispatch_async(dispatch_get_main_queue(), ^{ 

     NSURLRequest *theRequest_YT = [NSURLRequest requestWithURL:[NSURL URLWithString:url_YT]]; 
     NSURLConnection *theConnection_YT = [[NSURLConnection alloc] initWithRequest:theRequest_YT delegate:self]; 

     if (theConnection_YT) { 
      YT_JSON_FEED = [[NSMutableData alloc] init]; 
      NSLog(@"Respoce happening..."); 
     } 

     else { 
      NSLog(@"failed"); 
     } 
    }); 
}); 

while (icon_check == 0) { 
    NSLog(@"Wait"); 
} 

return icon_url; 
} 

/// Data loading /// 

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { 
    [YT_JSON_FEED setLength:0]; 
} 

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { 
    [YT_JSON_FEED appendData:data]; 
} 

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { 
    NSString *msg = [NSString stringWithFormat:@"Failed: %@", [error description]]; 
    NSLog(@"%@",msg); 
} 

-(void)connectionDidFinishLoading:(NSURLConnection *)connection { 

NSError *myError = nil; 
NSDictionary *feed = [NSJSONSerialization JSONObjectWithData:YT_JSON_FEED options:NSJSONReadingMutableLeaves error:&myError]; 

icon_url = [[[[[feed objectForKey:@"items"] valueForKey:@"snippet"] valueForKey:@"thumbnails"] valueForKey:@"default"] valueForKey:@"url"]; 

icon_check = 1; 
}

來源

2014-02-21 Supertecnoboff

請勿「檢查」。設置你的委託，當下載結束時你將被TOLD。 – matt

對於同步請求（阻塞，直到有東西返回），使用NSURLConnection的sendSynchronousRequest:returningResponse:error:代替。像這樣：

-(NSString *)get_user_icon:(NSString *)YT_ID { 

    NSString *url_YT = [NSString stringWithFormat:YOUT_profile_part_2, YT_ID]; 

    NSURLRequest *theRequest_YT = [NSURLRequest requestWithURL:[NSURL URLWithString:url_YT]]; 

    NSURLResponse* response = nil; 
    NSError* error = nil; 
    NSData* data = [NSURLConnection sendSynchronousRequest:theRequest_YT returningResponse:&response error:&error]; 

    //Check response and error for possible errors here. 

    //If no errors. 
    NSDictionary *feed = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&myError]; 

    icon_url = [[[[[feed objectForKey:@"items"] valueForKey:@"snippet"] valueForKey:@"thumbnails"] valueForKey:@"default"] valueForKey:@"url"]; 

    return icon_url; 
}

但是，這不建議。您需要將您的API更改爲異步。基於代理的，但更優選的是，使用基於塊的API。

來源

2014-02-21 18:48:05

謝謝你的幫助和解釋。我也將考慮使用基於塊的API。 – Supertecnoboff

如何檢查connectionDidFinishLoading何時完成

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