先轉成data 然後用系統自帶的JSON解析，解析成字典格式,

類方法如下,也可改為+改為-變成構造方法直接呼叫

+(NSDictionary *)parseJSONStringToNSDictionary:(NSString *)JSONString {
    NSData *JSONData = [JSONString dataUsingEncoding:NSUTF8StringEncoding];
    NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:JSONData options:NSJSONReadingMutableLeaves error:nil];
    return responseJSON;
}