Question 109323 in Json Question posted in
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Parse JSON in flutter – _InternalLinkedHashMap<String, dynamic>

I am trying to parse JSON in flutter. I tried with below code.

Sample JSON.

{
    "statusCode": 200,
    "message": "",
    "result": [
        {         
            "userName": "RAJ",
            "hierarchyLevel": 3,
            "sequence": 1,        
            "isSuccess": 1
        },
        {
            "userName": "SAM",
            "hierarchyLevel": 3,
            "sequence": 1,        
            "isSuccess": 1 
        },
       
    ]
}

My Code is:

                  int jsonStatus = response.statusCode;
                  if (jsonStatus == 200) {
                    var jsonData = json.decode(response.body);
                    if (jsonData["statusCode"] == 200) {
                      List<dynamic> listValJson = jsonData["result"];
                      List<String> userList = new List<String>.from(listValJson);
                    }
          }

I am getting below error:

Error: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String'

I know it is basic question for JSON parsing. I tried with Mapping also. But in this case I need list of "userName"’s presented in array. Kindly check my JSON

Tags:

3

Answers


  1. 0

    This error is simply says that you are trying to convert Map into String.

    List<dynamic> listValJson = jsonData["result"];

    now ‘listValJson’ is List<Map<String,dynamic>> not List<String>

    Try to create a data model for all user’s data or use

    if (jsonData["statusCode"] == 200) {
                  List<dynamic> listValJson = jsonData["result"];
                  List<String> userList = new List<String>.from(listValJson['userName']);
                }

    if you want to use only name.

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  2. 0

    result class

    class Result {
  String? userName;
  int? hierarchyLevel;
  int? sequence;
  int? isSuccess;

  Result({this.userName, this.hierarchyLevel, this.sequence, this.isSuccess});

  Result.fromJson(Map<String, dynamic> json) {
    userName = json['userName'];
    hierarchyLevel = json['hierarchyLevel'];
    sequence = json['sequence'];
    isSuccess = json['isSuccess'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['userName'] = this.userName;
    data['hierarchyLevel'] = this.hierarchyLevel;
    data['sequence'] = this.sequence;
    data['isSuccess'] = this.isSuccess;
    return data;
  }
}

    fix your response:

    final List<Result> listResult =
          (jsonData["result"] as List<dynamic>)
              .map((e) => Result.fromJson(e as Map<String, dynamic>))
              .toList();
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  3. 0

    For parsing the json, you should use the Model in dart and using the helpers like fromJson toJson you should contact with the API.

    You can use https://javiercbk.github.io/json_to_dart/, which will create the Model for you , if you paste the json.

    For example consider using a Model.

    class Model {
  String? userName;
  int? hierarchyLevel;
  int? sequence;
  int? isSuccess;

  Model({this.userName, this.hierarchyLevel, this.sequence, this.isSuccess});

  Model.fromJson(Map<String, dynamic> json) {
    userName = json['userName'];
    hierarchyLevel = json['hierarchyLevel'];
    sequence = json['sequence'];
    isSuccess = json['isSuccess'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['userName'] = this.userName;
    data['hierarchyLevel'] = this.hierarchyLevel;
    data['sequence'] = this.sequence;
    data['isSuccess'] = this.isSuccess;
    return data;
  }
}

    And use it as:

    final List<Result> result =   (jsonData["result"] as List<dynamic>)
                               .map((item) => Model.fromJson(item as Map<String, dynamic>))
                               .toList();

    Now you can access any of its child like:

    debugPrint(result[0].userName); // Raj
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