iOS 从网络获取son并解析

NSString* GXURL = PURL;
    GXURL = [GXURL stringByAppendingString:@"/index.php/Api/android_getRankByShow/eid/521"],GXURL;
    NSURL* url = [NSURL URLWithString:GXURL];
    NSString* gongxian = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];

    NSData * data = [gongxian dataUsingEncoding:NSUTF8StringEncoding];//将string 转换成 NSdata

    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];//将 NSdata转换成 字典

    //NSLog(@"%@",json);

    NSString* callBackData = [json valueForKey:@"data"];
    //NSLog(@"%@",callBackData);
    if([callBackData isEqual:@""])
    {

    }
    else
    {
        NSMutableArray *newList = [[NSMutableArray alloc] init];
        for(NSArray* item in callBackData)
        {
            NSString* nickname = [item valueForKey:@"nickname"];
            //NSLog(@"%@",nickname);

            NSString* gongxianStr = [NSString stringWithFormat:@"%@",nickname];
            [newList addObject:gongxianStr];

        }
        _list = newList;

        [_devoteTable reloadData];

    }