使用动态类型反序列化Json字符串时出错

Question

我有一个非常简单的类来尝试反序列化Json对象：

class UserFeedback {
  String text;
  String from;
  int hits;

  UserFeedback({
    this.text,
    this.from,
    this.hits,
  });

  factory UserFeedback.fromJson(Map<String, dynamic> json) => UserFeedback(
    text: json["text"],
    from: json["from"],
    hits: json["hits"],
  );


  Map<String, dynamic> toJson() => {
    "text": text,
    "from": from,
    "hits": hits,
  };
}

出于某种我不了解的原因，尝试反序列化以下Json部分时出现以下错误：

....
...
json continues
....
.... ,
"userFeedback": [
        {
          "text": "aer a arfafgaagakg agdfllfddfasa",
          "from": "userID-XXXXXX",
          "hits": "2"
        },
        {
          "text": "aer a arfafgaagakg agdfllfddfasa",
          "from": "userID-XXXXXX",
          "hits": "5"
        }
      ]
....
...
json continues
....
.... 

错误似乎与动态功能的使用有关，但是错误输出并没有太大帮助。

ERROR type '(dynamic) => UserFeedback' is not a subtype of type '(String, dynamic) => MapEntry<dynamic, dynamic>' of 'transform'