added controller for locations

lib/service/location_controller.dart

@@ -0,0 +1,33 @@
+import 'package:flutter/material.dart';
+
+import '../model/location.dart';
+import '../model/repositories/interfaces/location_repository.dart';
+
+class LocationController extends ChangeNotifier {
+  LocationController(LocationRepository repository) : _repository = repository {
+    _loadLocations();
+  }
+
+  final LocationRepository _repository;
+
+  final List<Location> _locations = [];
+
+  Future<void> addLocation(Location location) {
+    _locations.add(location);
+    notifyListeners();
+    return _repository.createLocation(location);
+  }
+
+  Future<void> deleteLocation(Location location) {
+    _locations.remove(location);
+    notifyListeners();
+    return _repository.deleteLocation(location);
+  }
+
+  Future<void> _loadLocations() {
+    _locations.clear();
+    return _repository.loadLocations().then(
+      (value) => _locations.addAll(value),
+    );
+  }
+}