问获取数据的Web服务在ios 6中返回null，但在ios 7中不返回

EN

 NSMutableData *serverData;
 //delegate methods for NSURLConnection
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
      NSString *str = [[NSString alloc] initWithData:serverData encoding:NSUTF8StringEncoding];//here i am initializing 
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
      [serverData appendData:data]; // here i get data that is null but i get response from server

}



Myviewwillappear code here...
- (void)viewWillAppear:(BOOL)animated {
[self performSelector:@selector(GetDataFromServer) withObject:nil afterDelay:0.001];
}
- (void) GetDataFromServer {
NSString *soapMessage = [NSString stringWithFormat:@"<?xml version=\"1.0\" encoding=\"utf-8\"?>"

                         @"<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">"

                         @"<soap:Body>"

                         @"<GetProductList xmlns=\"http://tempuri.org/\">"

                         @"<inCompany>%@</inCompany>"

                         @"<inUserName>%@</inUserName>"

                         @"<inType>%@</inType>"

                         @"<inTypeValue>%@</inTypeValue>"

                         @"<inSearchVal>%@</inSearchVal>"

                         @"<inPage>%@</inPage>"

                         @"</GetProductList>"

                         @"</soap:Body>"

                         @"</soap:Envelope>",Company,Username,type,typevalue,searchval,page];



NSURL *url = [NSURL URLWithString:PVBASE_URL];

NSString *msgLength = [NSString stringWithFormat:@"%d",[soapMessage length]];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

[request addValue:@"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];

[request addValue:PVPRODUCTLIST forHTTPHeaderField:@"SOAPAction"];

[request setHTTPMethod:@"POST"];

[request addValue:msgLength forHTTPHeaderField:@"Content-Length"];

[request setHTTPBody:[soapMessage dataUsingEncoding:NSUTF8StringEncoding]];

connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

if (connection) {



    if (serverData) {



        serverData = nil;

    }

    serverData = [[NSMutableData alloc] init];

}

connection = nil;
}