我无法使用解析的整数进行 api 调用答案

【问题标题】：I can't manage to make an api call using a parsed integer我无法使用解析的整数进行 api 调用
【发布时间】：2020-08-27 08:43:39
【问题描述】：

所以我正在使用颤振构建应用程序，我是颤振新手，需要一些帮助。

因此，就上下文而言，我的应用程序连接到一个 REST API，该 API 与一个虚构的电梯公司的 ruby on rails 网络应用程序相关联（用于学习目的），我想要实现的是改变在我的应用程序中使用文本字段的电梯，我几乎明白了，唯一的事情是，每当我像这样进行 api 调用时：

class DetailScreen extends StatelessWidget {
  // Declare a field that holds the Todo.
  final Elevator elevator;

  // In the constructor, require a Todo.
  DetailScreen({Key key, @required this.elevator}) : super(key: key);

  Future _changeStatus(elevator) async {
    //Fetch the data from the api
    // ignore: non_constant_identifier_names
    var id = elevator.id.toString();
    var holder = id.toString();
    var url = 'https://rocketcrybaby.azurewebsites.net/api/elevators/'+holder;
    var response = await http.put(
        url, body: {'status': '${_statusController.text}'});
    if (_statusController.text != "active"|| _statusController.text != "inactive"){
      return "Error not a valid status !";
    }
    print('Response status: ${response.statusCode}');
    print('Response body: ${response.body}');

    //print(await http.read('https://example.com/foobar.txt'));
   return "sucess";
  }



  @override
  Widget build(BuildContext context) {
    // Use the Todo to create the UI.
    return Scaffold(
      appBar: AppBar(
        title: Text("Elevator # " +elevator.id.toString()),
      ),
      body: Center(
        child: Center(
          child: TextField(
            controller: _statusController
          ),
        )
      ),
      floatingActionButton: FloatingActionButton(onPressed: () async => [ await _changeStatus(elevator.id.toString()), print(elevator.status)]),


    );
  }

它返回给我这个错误：

 E/flutter (18441): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: NoSuchMethodError: Class 'String' has no instance getter 'id'.
E/flutter (18441): Receiver: "3"
E/flutter (18441): Tried calling: id

我真的不知道该怎么做了我尝试了我书中的每一个技巧：/

这里是电梯类的参考

class Elevator {
  final String status;
  final String model;
  final int id;

  Elevator({this.status, this.model, this.id}); //Elevator Constructor

  factory Elevator.fromJson(Map<String, dynamic> json) { //Parse the infos as Json String
    return Elevator(
      status: json['status'],
      model: json['model'],
      id: json['id']
    );
  }


}

另外这是我的 api 中电梯的输出


{
        "id": 3,
        "column_id": 1,
        "serial_number": 7204019747089,
        "model": "Excelium",
        "building_type": "Hybrid",
        "status": "Inactive",
        "date_service_since": "2018-03-09T00:00:00",
        "date_last_inspection": "2019-02-19T00:00:00",
        "inspection_certificate": "Yes",
        "information": "Dori",
        "notes": "Dolores aut et. Ea optio rem. Provident exercitationem ut.",
        "created_at": "2020-04-09T20:41:55",
        "updated_at": "2020-04-09T20:41:55"
    },

【问题讨论】：

标签： android rest flutter dart mobile

【解决方案1】：

解决方案：

class DetailScreen extends StatelessWidget {
  // Declare a field that holds the Todo.
  final Elevator elevator;

  // In the constructor, require a Todo.
  DetailScreen({Key key, @required this.elevator}) : super(key: key);

  Future _changeStatus(Elevator  elevator) async {
    //Fetch the data from the api
    // ignore: non_constant_identifier_names
    var id = elevator.id.toString();
    var holder = id.toString();
    var url = 'https://rocketcrybaby.azurewebsites.net/api/elevators/'+holder;
    var response = await http.put(
        url, body: {'status': '${_statusController.text}'});
    if (_statusController.text != "active"|| _statusController.text != "inactive"){
      return "Error not a valid status !";
    }
    print('Response status: ${response.statusCode}');
    print('Response body: ${response.body}');

    //print(await http.read('https://example.com/foobar.txt'));
   return "sucess";
  }



  @override
  Widget build(BuildContext context) {
    // Use the Todo to create the UI.
    return Scaffold(
      appBar: AppBar(
        title: Text("Elevator # " +elevator.id.toString()),
      ),
      body: Center(
        child: Center(
          child: TextField(
            controller: _statusController
          ),
        )
      ),
      floatingActionButton: FloatingActionButton(onPressed: () async => [ await _changeStatus(elevator), print(elevator.status)]),


    );
  }

提示：在声明变量时始终使用变量类型以避免这些错误和良好做法。

谢谢。

【讨论】：

【解决方案2】：

那是因为您的方法：Future _changeStatus(elevator) async 实际上需要 Elevator elevator，但您提供的是 elevator.id.toString()，这是一个字符串。

更改方法参数的类型并在FAB的onPressed中更改为等待_changeStatus(elevator)。

【讨论】：