iOS-NSURLConnection异步发送 HTTP请求

- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar

{
 NSString *new = [searchBar.text stringByReplacingOccurrencesOfString:@" " withString:@"+"];
 NSString *urlString = [NSString stringWithFormat:@"http://192.168.1.104/test.php?cid=%@",new];
 NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding (kCFStringEncodingGB_18030_2000);
  NSString *strUrld8 = [urlString stringByAddingPercentEscapesUsingEncoding:enc];
 //调用http get请求方法 
 [self sendRequestByGet:strUrld8];
}
//HTTP get请求方法
- (void)sendRequestByGet:(NSString*)urlString
{  
 NSURL *url=[NSURL URLWithString:urlString];
 NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url
                cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
               timeoutInterval:60];
 //设置请求方式为get
 [request setHTTPMethod:@"GET"];
 //添加用户会话id
 [request addValue:@"text/html" forHTTPHeaderField:@"Content-Type"];
 //连接发送请求
 receivedData=[[NSMutableData alloc] initWithData:nil];
 NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
 [request release];      
 [conn release];
}

- (void)connection:(NSURLConnection *)aConn didReceiveResponse:(NSURLResponse *)response {
    // 注意这里将NSURLResponse对象转换成NSHTTPURLResponse对象才能去
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response;
    if ([response respondsToSelector:@selector(allHeaderFields)]) {
        NSDictionary *dictionary = [httpResponse allHeaderFields];
        NSLog(@"[email=dictionary=%@]dictionary=%@",[dictionary[/email] description]);
  
    }
}
//接收NSData数据
- (void)connection:(NSURLConnection *)aConn didReceiveData:(NSData *)data {
 [receivedData appendData:data];
}
- (void)connection:(NSURLConnection *)aConn didFailWithError:(NSError *)error{
 NSLog(@"[email=error=%@]error=%@",[error[/email] localizedDescription]);
}
//接收完毕,显示结果
- (void)connectionDidFinishLoading:(NSURLConnection *)aConn {
   NSString *results = [[NSString alloc]
                         initWithBytes:[receivedData bytes]
                         length:[receivedData length]
                         encoding:NSUTF8StringEncoding];
 NSLog(@"results=%@",results);
}