SBJson

    //{"code":"login_success","message":"abcdeeeee"}
    //以{}表示的是字典 
    //“:”key，value分隔符
    //“，”元素分隔符
    
    NSString* str = @"{\"code\":\"login_success\",\"message\":\"abcedsdfsdf\"}";
    
    NSDictionary* dic = [str JSONValue];
    
    NSString* codeStr = [dic objectForKey:@"code"];
    NSString* messageStr = [dic objectForKey:@"message"];
    
    NSLog(@"%@",codeStr);
    NSLog(@"%@",messageStr);

    //["a","b","c"]
    //[]表示的是一个数组
    
    str = @"[\"a\",\"b\",\"c\"]";
    NSArray* array = [str JSONValue];
    for (NSString* str in array) {
        NSLog(@"%@",str);
    }

    //{"num":"3","names":["a","b","c"]}
    str = @"{\"num\":\"3\",\"names\":[\"a\",\"b\",\"c\"]}";
    NSDictionary* jsonDic = [str JSONValue];
    NSLog(@"%@",[jsonDic objectForKey:@"num"]);
    NSArray* jsonArray = [jsonDic objectForKey:@"names"];
    NSLog(@"%@",jsonArray);

    //[NSString stringWithContentsOfURL:]
    NSString* urlStr = @"http://192.168.88.8/sns/my/user_list.php";
    NSURL* url = [NSURL URLWithString:urlStr];
    NSString* jsonStr = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
    dic = [jsonStr JSONValue];
    NSLog(@"%@",[dic objectForKey:@"totalcount"]);

    //NSURL->NSData
    NSData* data = [NSData dataWithContentsOfURL:url];
    
    //NSData->NSString
    str = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
    
    
    //NSString->NSData
    //data = [str dataUsingEncoding:NSUTF8StringEncoding];
    
    //NSData->UIImage
    //UIImage* image = [UIImage imageWithData:data];
    
    //UIImage->NSData
    //data = UIImagePNGRepresentation(image);