iOS Http請求異步請求

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.


_data = [[NSMutableData alloc] init];

// 組合一個搜索字符串
NSString *urlStr = [NSString stringWithFormat:@"http://www.baidu.com/s?wd=%@", @"php"];
NSURL *url = [NSURL URLWithString:urlStr];

NSURLRequest *request = [NSURLRequest requestWithURL:url];

//發起請求，定義代理
[NSURLConnection connectionWithRequest:request delegate:self];


}
// 分批返回數據

(void)connection:(NSURLConnection ) connection didReceiveData:(NSData )data {
  [_data appendData:data];
  NSLog(@"%@", _data);
}

// 數據完全返回完畢

(void)connectionDidFinishLoading:(NSURLConnection )connection {
  NSString dataString =  [[NSString alloc] initWithData:_data encoding:NSUTF8StringEncoding];
  NSLog(@"%@", dataString);
}</pre>