如何為JOSN撰寫模型？撲

我有一個 Google 地圖 API，其中我試圖在 SQFLite 中保存該特定位置的位置鍵和 JSON 回應。我能夠撰寫 fromJSON 方法，但如何撰寫 toMap 方法？

這是沒有 toMap 方法的模型

class GeometryModel {
  final LocationModel locationModel;

  GeometryModel({required this.locationModel});

  factory GeometryModel.fromJson(Map<dynamic, dynamic> parsedJson) {
    return GeometryModel(locationModel: LocationModel.fromJson(parsedJson['location']));
  }
}

class LocationModel {
  final double latitude;
  final double longitude;

  LocationModel({required this.latitude, required this.longitude});

  factory LocationModel.fromJson(Map<dynamic, dynamic> parsedJson) {
    return LocationModel(latitude: parsedJson['lat'], longitude: parsedJson['lng']);
  }
}

class PlaceModel {
  final String placeId;
  final GeometryModel geometryModel;
  final String address;
  final String name;

  PlaceModel({required this.placeId, required this.geometryModel, required this.address, required this.name});

  factory PlaceModel.fromJson(Map<String, dynamic> parsedJson) {
    return PlaceModel(
        placeId: parsedJson['place_id'],
        name: parsedJson['vicinity'],
        geometryModel: GeometryModel.fromJson(parsedJson['geometry']),
        address: parsedJson['formatted_address'],
    );
  }
}

這是我從服務器收到的回應

{
    "html_attributions": [],
    "result": {
        "formatted_address": "New York, NY, USA",
        "geometry": {
            "location": {
                "lat": 40.7127753,
                "lng": -74.0059728
            },
            "viewport": {
                "northeast": {
                    "lat": 40.91757705070789,
                    "lng": -73.70027206817629
                },
                "southwest": {
                    "lat": 40.47739906045452,
                    "lng": -74.25908991427882
                }
            }
        },
        "icon_background_color": "#7B9EB0",
        "icon_mask_base_uri":  "https://maps.gstatic.com/mapfiles/place_api/icons/v2/generic_pinlet",
        "name": "New York"
        "url": "https://maps.google.com/?q=New York, NY, USA&ftid=0x89c24fa5d33f083b:0xc80b8f06e177fe62",
        "utc_offset": -240,
        "vicinity": "New York","
    },
    "status": "OK"
}

uj5u.com熱心網友回復：

使用JsonToDart網站。您只需要粘貼 JSON 資料，它就會將 json 資料與fromJson()andtoJson()或一起轉換為模型類toMap()。

注意：如果您收到 json 語法錯誤，您需要驗證您的 json 資料是否有效。對于 json 驗證檢查json_parser_online網站。

uj5u.com熱心網友回復：

還有另一個選項可以處理 JSON 資料，無需創建模型，也無需使用生成器！如何？使用g-json 包。

Naan Avan，請參閱我對另一個問題的回答（如何使用 Flutter 中的默認方法決議復雜的 JSON？）。

uj5u.com熱心網友回復：

這是示例Viewport，如何轉換 toJson/toMap 并使用此鏈接幫助您將 JSON 轉換為 map

class Viewport {
  Viewport viewport;

  Viewport({this.viewport});

  Viewport.fromJson(Map<String, dynamic> json) {
    viewport = json['viewport'] != null
        ? new Viewport.fromJson(json['viewport'])
        : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.viewport != null) {
      data['viewport'] = this.viewport.toJson();
    }
    return data;
  }
}

class Viewport {
  Northeast northeast;
  Northeast southwest;

  Viewport({this.northeast, this.southwest});

  Viewport.fromJson(Map<String, dynamic> json) {
    northeast = json['northeast'] != null
        ? new Northeast.fromJson(json['northeast'])
        : null;
    southwest = json['southwest'] != null
        ? new Northeast.fromJson(json['southwest'])
        : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.northeast != null) {
      data['northeast'] = this.northeast.toJson();
    }
    if (this.southwest != null) {
      data['southwest'] = this.southwest.toJson();
    }
    return data;
  }
}

class Northeast {
  double lat;
  double lng;

  Northeast({this.lat, this.lng});

  Northeast.fromJson(Map<String, dynamic> json) {
    lat = json['lat'];
    lng = json['lng'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['lat'] = this.lat;
    data['lng'] = this.lng;
    return data;
  }
}

uj5u.com熱心網友回復：

你可以這樣實作：

  Map<String, dynamic> toMap() {
var map = Map<String, dynamic>();
map['place_id'] = placeId;
map['address'] = address;
map['name'] = name;
map['geometry_model_id']=geometryModel.id; //saves id
return map;}

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