iOS AFNetWorking 请求json数据

    NSString *str=[NSString stringWithFormat:@"http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=json&ip=218.4.255.255"];

NSURL *url = [NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];                        // UTF－8
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];
// 请求数据，设置成功与失败的回调函数
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSString *html = operation.responseString;
    NSData* data=[html dataUsingEncoding:NSUTF8StringEncoding];
    id dict=[NSJSONSerialization  JSONObjectWithData:data options:0 error:nil];
    NSLog(@"获取到的数据为：%@",dict);
}failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"发生错误！%@",error);
}];
// 加入队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[queue addOperation:operation];</pre>