NSURLConnection 不接收数据

Question

我已经实现了一个NSURLConnection，它向服务器发送请求并接收一些存储在NSMutableData 对象中的数据。这些是我作为NSURLConnectionDelegate 的一部分实现的方法：

-(void)upLoadBook:(NSMutableDictionary *)theOptions{

NSMutableString *theURL = [[NSMutableString alloc] initWithString:@"theURL"];

[theURL appendFormat:@"&Title=%@&Author=%@&Price=%@",  [theOptions objectForKey:@"bookTitle"], 
                                                       [theOptions objectForKey:@"bookAuthor"], 
                                                       [theOptions objectForKey:@"bookPrice"]];
[theURL appendFormat:@"&Edition=%@&Condition=%@&Owner=%@", [theOptions objectForKey:@"bookEdition"],
                                                        [theOptions objectForKey:@"bookCondition"],
                                                        _appDel.userID];

NSLog(@"%@\n", theURL);
NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:theURL]
                                            cachePolicy:NSURLRequestUseProtocolCachePolicy
                                        timeoutInterval:10.0];
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (theConnection) {
    // Create the NSMutableData to hold the received data.
    // receivedData is an instance variable declared elsewhere.
    receivedData = [NSMutableData data];
}
}

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

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse      
  *)response
 {
// This method is called when the server has determined that it
// has enough information to create the NSURLResponse.

// It can be called multiple times, for example in the case of a
// redirect, so each time we reset the data.

// receivedData is an instance variable declared elsewhere.
[receivedData setLength:0];
}

 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
   // do something with the data
  // receivedData is declared as a method instance elsewhere

//Receives a response after book has been uploaded (Preferably a Book ID...)
  responseString = [[NSString alloc] initWithData:receivedData         
 encoding:NSUTF8StringEncoding];

NSLog(@"Response String: %@", responseString);
[_options setValue:responseString forKey:@"bookID"];

[self performSegueWithIdentifier:@"UploadSuccessSegue" sender:self];

}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Whoops." message:@" No internet     
connection.\n Please make sure you have a connection to the internet." 
                                               delegate:self cancelButtonTitle:@"Ok"   
otherButtonTitles: nil];
[alert show];
}

函数uploadBook 似乎被调用，但是，我从来没有到达didFinishLoading 和didReceiveData 从来没有收到任何数据。可能是什么问题。任何提示或线索将不胜感激。

Answer 1

您需要将您的 NSURLConnection 添加到当前运行循环或单独的一个（例如您在单独的线程中设置的一个）。毕竟，委托方法确实需要获取 CPU 时间。

Looking at this related question's accepted answer，也可以通过Grand Central Dispatch：

dispatch_async(dispatch_get_main_queue(), ^{
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
    [conn start];
});

Answer 2

可以肯定的是，在尝试发送请求之前，您应该 %-escape 您的参数列表。

您可以为此目的使用stringByAddingPercentEscapesUsingEncoding：

NSMutableString *theURL = [[NSMutableString alloc] initWithString:@""];

[theURL appendFormat:@"&Title=%@&Author=%@&Price=%@",  [theOptions objectForKey:@"bookTitle"], 
                                                   [theOptions objectForKey:@"bookAuthor"], 
                                                   [theOptions objectForKey:@"bookPrice"]];
[theURL appendFormat:@"&Edition=%@&Condition=%@&Owner=%@", [theOptions objectForKey:@"bookEdition"],
                                                    [theOptions objectForKey:@"bookCondition"],
                                                    _appDel.userID];


 theURL = [NSStringWithFormat:@"YOUR_URL_HERE?",[theURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

请注意，我以最少的更改次数重构了您的代码以获得结果。你肯定能找到更好的重构。

Answer 3

这是我的一个项目的示例：

NSMutableURLRequest *urlRequest = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://www.brayden.me/analytics/device.php"]];
[urlRequest setHTTPMethod:@"POST"];

NSMutableString *postParams = [NSMutableString string];
[postParams appendFormat:@"session=%@&", analyticsSession];
[postParams appendFormat:@"device=%@&", device];
[postParams appendFormat:@"system=%@&", csystem];
[postParams appendFormat:@"version=%@&", version];
[postParams appendFormat:@"launch=%f&", totalLaunchTime];

if([Analytics_Location location].latitude && [Analytics_Location location].longitude) {
    [postParams appendFormat:@"latitude=%@&", [Analytics_Location location].latitude];
    [postParams appendFormat:@"longitude=%@&", [Analytics_Location location].longitude];
}

[urlRequest setHTTPBody:[postParams dataUsingEncoding:NSUTF8StringEncoding]];

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self startImmediately:YES];
[connection start];

确保您的标头方法也使用 .我的代码至少应该向您展示如何正确格式化请求，因为我可以验证这确实从我的 PHP 调用接收数据。