changed difficulty logic

lib/models/difficulty.dart

@@ -1,8 +1,8 @@
-class Difficulty {
+class DifficultyUtil {
   static List<String> get difficulties {
-    return List<String>.generate(_Difficulty.values.length,
-        (index) => _Difficulty.values.elementAt(index).name);
+    return List<String>.generate(Difficulty.values.length,
+        (index) => Difficulty.values.elementAt(index).name);
   }
 }
 
-enum _Difficulty { veryEasy, easy, intermediate, hard, veryHard }
+enum Difficulty { veryEasy, easy, intermediate, hard, veryHard }

lib/models/recipe.dart

@@ -5,7 +5,7 @@ import 'steps.dart';
 class Recipe {
   final String title;
   final String description;
-  final Difficulty? difficulty;
+  final DifficultyUtil? difficulty;
   final List<Ingredient> ingredients = [];
   final Steps steps = Steps();