How to solve this List<dynamic> type error in Flutter/Dart - flutter

Question

I am very new to flutter and dart. Trying to return a list from this future that pulls data from an api but I keep getting this error. Someone here helped me solve a similar error by casting to a list because I was calling map function on an array that returns an iterable but in this case here I'm not sure what needs to be done.
type List<dynamic> is not a subtype of type FutrueOr<ListCity>>
Data is received like below:
{
"data": {
"127287": {
"Feature_int_id": "127287",
"Admin1_str_code": "US06",
"Country_str_code": "US",
"Feature_str_name": "Acampo",
"Feature_dec_lat": "38.194",
"Feature_dec_lon": "-121.25"
},
"116496": {
"Feature_int_id": "116496",
"Admin1_str_code": "US06",
"Country_str_code": "US",
"Feature_str_name": "Acton",
"Feature_dec_lat": "34.49",
"Feature_dec_lon": "-118.22"
},
"124284": {
"Feature_int_id": "124284",
"Admin1_str_code": "US06",
"Country_str_code": "US",
"Feature_str_name": "Adelanto",
"Feature_dec_lat": "34.665",
"Feature_dec_lon": "-117.512"
},
}
Below is the code for future:
Future<List<City>> fetchCitiesByProvince(provinceCode) async {
final response = await http.get(Uri.https('localhost/msd', 'api/cities/' + provinceCode));
final responseJson = json.decode(response.body);
final dataMap = responseJson['data'];
if (response.statusCode == 200) {
List citiesList = [];
for (var city in dataMap.keys) {
if (dataMap[city]['Admin1_str_code'] == provinceCode) {
citiesList.add(
{
'cityCode': dataMap[city]['Feature_int_id'],
'cityName': dataMap[city]['Feature_str_name']
}
);
}
}
return citiesList;
} else {
throw Exception('Failed to load cities');
}
}
City Class:
class City {
final String cityCode;
final String cityName;
City({#required this.cityCode, #required this.cityName});
factory City.fromJson(Map<String, dynamic> json) {
return City(
cityCode: json['Feature_int_id'],
cityName: json['Feature_str_name']
);
}
}

Answer 1

You need to return List<City> in your method. So, change the following code:
List citiesList = [];
to
List<City> citiesList = [];
--- UPDATE ---
You need to user your City constructor or factory to generate the item from json like this:
City.fromJson(dataMap[city]);
// Or
City(cityCode: dataMap[city]['Feature_int_id'],
cityName: dataMap[city]['Feature_str_name']
);
Here the updated sample code:
Future<List<City>> fetchCitiesByProvince(provinceCode) async {
final response = await http.get(Uri.https('localhost/msd', 'api/cities/' + provinceCode));
final responseJson = json.decode(response.body);
final dataMap = responseJson['data'];
List<City> citiesList = [];
if (response.statusCode == 200) {
for (var city in dataMap.keys) {
if (dataMap[city]['Admin1_str_code'] == provinceCode) {
citiesList.add(City.fromJson(dataMap[city]));
}
}
} else {
throw Exception('Failed to load cities');
// either throwing an error or return empty list.
}
return citiesList;
}