The method 'fromMap' isn't defined for the type 'Trending'

FirebaseFirestore.instance
    .collection('admin')
    .doc('Geofence')
    .get()
    .then((value) {
  geofenceModel = geofenceModel.fromMap//error here(value.data());
  setState(() {
    latitude = ("${geofenceModel.latitude}");
    longitude = ("${geofenceModel.longitude}");
    radius = ("${geofenceModel.radius}");
  });
});

the error start from the "fromMap". Please help me to solve it

Assuming you have the parameters you mentioned (lat, long, rad) as type String for your GeoFenceModel, you need to create the fromMap() as follows:

class GeofenceModel {
  String latitude;
  String longitude;
  String radius;
  GeofenceModel({
    required this.latitude,
    required this.longitude,
    required this.radius,
  });

  Map<String, dynamic> toMap() {
    return <String, dynamic>{
      'latitude': latitude,
      'longitude': longitude,
      'radius': radius,
    };
  }

  factory GeofenceModel.fromMap(Map<String, dynamic> map) {
    return GeofenceModel(
      latitude: (map['latitude'] ?? '') as String,
      longitude: (map['longitude'] ?? '') as String,
      radius: (map['radius'] ?? '') as String,
    );
  }
}