Have tried to create a List of objects out of a json file.

I get this error: Error: Expected a value of type 'Iterable', but got one of type '_JsonMap'

Future <List<Inspection>> FutureInspections() async {
    var inspections = <Inspection>[]; 
    final String response = await rootBundle.loadString('assets/sample.json');
      var inspectionsJson = json.decode(response); 
      for (var inspectionJson in inspectionsJson) {
        inspections.add(Inspection.fromJson(inspectionJson));
      }
    return inspections;
  }

[Update 03.11.2021 Inspection class]

class Inspection
{
  String _description="";
  int _interval=0;
  int _state=0;
  DateTime _date=new DateTime.now();

  Inspection(this._description, this._interval, this._state, this._date);

  Inspection.fromJson(Map<String, dynamic>json){
    _description=json['description'];
    _interval=json['interval'];
    _state=json['state'];
    _date=json['date'];
  }


  DateTime get date => _date;

  set date(DateTime value) {
    _date = value;
  }

  int get state => _state;

  set state(int value) {
    _state = value;
  }

  int get interval => _interval;

  set interval(int value) {
    _interval = value;
  }

  String get description => _description;

  set description(String value) {
    _description = value;
  }
}

the error pops up at this part of the code:

inspections.add(Inspection.fromJson(inspectionJson));

[Update 03.11.2021 Json-File] Json-File:

{
    "inspections": [
        {
            "date": "01.01.2021",
            "state": "1",
            "interval": "7",
            "description": "SampleText1"
        },
        {
            "date": "01.01.2021",
            "state": "2",
            "interval": "3",
            "description": "SampleText2"
        }
    ]
}

I don't understand why. Can you please help me?

CodePudding user response：

Response of json.decode is a _JsonMap. Out of it, extract the inspections as below.

Future<List<Inspection>> FutureInspections() async {
………

var inspectionsJson = json.decode(response);

final inspect = inspectionsJson['inspections'];   <———

for (var resp in inspect) {
  inspections.add(Inspection.fromJson(resp));
}
return inspections;
}

Also the json sample shown has String type for interval and state, String for date variable, but the Inspection class has int and DateTime types.This might need to change to String. After the values are put as String, they can be later converted to the desired type.