错误:NoSuchMethodError:方法"toDouble"在null上被调用.接收方:null尝试调用:toDouble() [英] ERROR: NoSuchMethodError: The method 'toDouble' was called on null. Receiver: null Tried calling: toDouble()

问题描述

我正在尝试使用fromJson函数来解析json文件.但是在运行测试时，我收到此错误消息.

错误:NoSuchMethodError:方法'toDouble'在null上调用.接收者:null尝试调用:toDouble()

我不确定这是怎么回事.

我的代码

weather_model_app_test.dart

  group('fromJson'，(){测试(应返回有效模型"，()异步{最终Map< String，dynamic>jsonMap =json.decode(fixture('weather_app.json'));//行为最终结果= WeatherAppModel.fromJson(jsonMap);//断言Expect(结果，tWeatherAppModel);});}); 

weather_app_model.dart

 工厂WeatherAppModel.fromJson(Map< String，dynamic> json){返回WeatherAppModel(weatherMain:json ['weather'] [0] ['main']，weatherDescription:json ['weather'] [0] ['description']，temp:(json ['main'] ['temp']为double).toDouble()，minTemp:(json ['main'] ['temp_min']为double).toDouble()，maxTemp:(json ['main'] ['temp_main']为double).toDouble()，国家/地区:json ['sys'] ['country']，);} 

fixtures/weather_app.dart

  {"coord":{"lon":78，"lat":20}，天气": [{"id":500，"main":雨"，"description":小雨"，"icon":"10d"}]，"base":"model"，主要的": {温度":301.51，压力":1014，湿度":67，"temp_min":301.51，"temp_max":301.51，海平面":1014，"grnd_level":979}，风": {速度":3.19，度":77}，雨": {"3小时":1.81}，云":{全部":45}，"dt":1577262029，"sys":{"country":"IN"，日出":1572655775，日落":1572696807}，时区":19800，"id":1272596，"name":"Digras"，鳕鱼":200} 

解决方案

不应 maxTemp:(json ['main'] ['temp_main'] as double).toDouble()，

在您的weather_app_model.dart文件中是 [temp_max] 而不是 [temp_main] ?

I am trying to make fromJson function which parse the json file. But while running test I am getting this error saying.

ERROR: NoSuchMethodError: The method 'toDouble' was called on null. Receiver: null Tried calling: toDouble()

I am not sure what is wrong with this.

My code

weather_model_app_test.dart

group('fromJson', () {
    test('should return a valid model', () async {
      final Map<String, dynamic> jsonMap =
          json.decode(fixture('weather_app.json'));
      //act
      final result = WeatherAppModel.fromJson(jsonMap);
      //assert
      expect(result, tWeatherAppModel);
    });
  });

weather_app_model.dart

factory WeatherAppModel.fromJson(Map<String, dynamic> json) {
    return WeatherAppModel(
      weatherMain: json['weather'][0]['main'],
      weatherDescription: json['weather'][0]['description'],
      temp: (json['main']['temp'] as double).toDouble(),
      minTemp: (json['main']['temp_min'] as double).toDouble(),
      maxTemp: (json['main']['temp_main'] as double).toDouble(),
      country: json['sys']['country'],
    );
  }

fixtures/weather_app.dart

{
  "coord": {
    "lon": 78,
    "lat": 20
  },
  "weather": [
    {
      "id": 500,
      "main": "Rain",
      "description": "light rain",
      "icon": "10d"
    }
  ],
  "base": "model",
  "main": {
    "temp": 301.51,
    "pressure": 1014,
    "humidity": 67,
    "temp_min": 301.51,
    "temp_max": 301.51,
    "sea_level": 1014,
    "grnd_level": 979
  },
  "wind": {
    "speed": 3.19,
    "deg": 77
  },
  "rain": {
    "3h": 1.81
  },
  "clouds": {
    "all": 45
  },
  "dt": 1572672029,
  "sys": {
    "country": "IN",
    "sunrise": 1572655775,
    "sunset": 1572696807
  },
  "timezone": 19800,
  "id": 1272596,
  "name": "Digras",
  "cod": 200
}

解决方案

Shouldn't maxTemp: (json['main']['temp_main'] as double).toDouble(),

be [temp_max] instead of [temp_main] in your weather_app_model.dart file?

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