解析嵌套的 json 失败颤振

Question

我有这个 json 响应，其中包含服务类型、车辆型号、附件、工作状态作为数组，但我无法访问任何类，当我打印 print(obj); 时它只显示 null

Json 文件

{
  "success": true,
  "message": "",
  "data": {
    "service_types": [
      {
        "id": 1,
        "name": "Car Wash"
      },
      {
        "id": 2,
        "name": "Full Body Wash"
      },
      {
        "id": 3,
        "name": "Polishing"
      },
      {
        "id": 4,
        "name": "Engine Oil Checkup"
      },
     
    ],
    "vehicle_models": [
      {
        "id": 1,
        "name": "SUV"
      }
    ],
    "accessories": [
      {
        "id": 2,
        "name": "Mat Cover"
      },
      {
        "id": 4,
        "name": "Cash"
      },
      {
        "id": 5,
        "name": "Engine Room washing"
      }
    ],
    "working_statuses": [
      {
        "id": 0,
        "name": "Registered"
      },
      {
        "id": 1,
        "name": "Work started"
      },
      {
        "id": 2,
        "name": "Work completed"
      },
      {
        "id": 5,
        "name": "Cancelled"
      }
    ]
  }
}

数据提取代码

var response = await http.post(Uri.parse(Urls.DasboardData),
    headers: {"Content-Type": "application/json"},
    body: json.encode({
      "vehicle_models": "",
      "service_types": "",
      "station_id":Station_id,
      "accessories": "",
      "working_statuses": "",
    }));

Map<String, dynamic> value = json.decode(response.body);

var data = value['data'];
if (data.length > 0) {
  
    for (int i = 0; i < data.length; i++) {
    var obj = data[i];
     print(obj);
    var service_type_obj = obj['service_types'];
    var vehicle_models_obj = obj['vehicle_models'];
    var accessories_obj = obj['accessories'];
    var working_statuses_obj = obj['working_statuses'];
    DataList.add(GetAllModel(
      service_type_obj['id'],
      service_type_obj['name'],
      vehicle_models_obj['id'],
      vehicle_models_obj['name'],
      accessories_obj['id'],
      accessories_obj['name'],
      working_statuses_obj['id'],
      working_statuses_obj['name'],
    ));
  }

  setState(() {
    print("UI UPDATED");
  });
}
else
  {

  } 

型号

class GetAllModel {
  String service_type_id,
        service_type_name,
        vehicle_models_id,
        vehicle_models_name,
        accessories_id,
        accessories_name,
        working_statuses_id,
       working_statuses_name;


  GetAllModel(
      this.service_type_id,
      this.service_type_name,
      this.vehicle_models_id,
      this.vehicle_models_name,
      this.accessories_id,
      this.accessories_name,
      this.working_statuses_id,
      this.working_statuses_name,
      );
}

Answer 1

问题是在迭代你的信息时，数据大小是4，但是这个它包含4个对象，因此你将无法访问data[i]，因为data[i]不存在，如果它存在数据 ['service_types'] 这是一个列表，如果您可以迭代包含对象的信息，请在此处。

因此，为了能够访问对象的信息，您必须像这样迭代它们：

for (var i = 0; i < data['service_types'].length; i++) {
   print(data['service_types'][i]);
}

其他对象也一样。

迭代的替代方法：

for (var item in data.values) {
   print(item);
}

Answer 2

你需要改变这些：

var service_type_obj = obj['service_types'];
var vehicle_models_obj = obj['vehicle_models'];
var accessories_obj = obj['accessories'];
var working_statuses_obj = obj['working_statuses'];

进入这个：

var service_type_obj = obj['service_types'][0];
var vehicle_models_obj = obj['vehicle_models'][0];
var accessories_obj = obj['accessories'][0];
var working_statuses_obj = obj['working_statuses'][0];

您的对象位于列表中，要访问它们，您必须使用索引，例如[0]。