问题描述

我在一个flutter项目中，使用异步请求api，并且用async函数封装，返回的是一个Future<ClassResponseData>

Future<ClassResponseData> getTimeTableFromStudentID(
    String studentId, String token) async {
  Options options = Options(headers: {HttpHeaders.authorizationHeader: token});
  Response response = await Dio()
      .post(
          "${StackConfig.ApiUrlHead}/api/pc/${StackConfig.ApiVersion}/timetables/getTimeTableFromStudentID",
          data: {"student_id": studentId, "year": "2020-2021", "semester": 1},
          options: options)
      .catchError((e) {
    print(e);
  });
  if (response != null) {
    return ClassResponseData.fromJson(response.data);
  } else {
    return null;
  }
}

我如何获取到Future<ClassResponseData>中的ClassResponseData，并赋值给一个变量？

尝试过的方法

创建一个类，用于获取Future里的数据

class ResponseDataFromAsync {
  ClassResponseData _data;
  String studentId;
  String token;

  ResponseDataFromAsync(this.studentId, this.token);

  set Class_data(ClassResponseData value) {
    //报错：Expected a value of type 'ClassResponseData', but got one of type '_Future<ClassResponseData>'
    //this._data = setData(this.studentId, this.token) as ClassResponseData;
    
    //报错：this._data=null;
    setData(this.studentId, this.token).then((data) {
      this._data = data;
    });
  }

  ClassResponseData get Class_data {
    return _data;
  }

  Future<ClassResponseData> setData(String studentId, String token) async {
    return await getTimeTableFromStudentID(studentId, token);
  }
}

还是无法解决

虽然对 Dart 不是很熟，但是猜想和 JS 差不多：

Future<ClassResponseData> setData(String studentId, String token) async {
    this._data = await getTimeTableFromStudentID(studentId, token);
}

不过此时 setData 没有返回值，所以要修改 <ClassResponseData> 这个类型！

ClassResponseData result = await setData(String studentId, String token);
或者
ClassResponseData result;
setData(String studentId, String token).then(ClassResponseData data) {
result = data;
};