added difficulty class and dropdown

lib/models/difficulty.dart

@@ -0,0 +1,8 @@
+class Difficulty {
+  static List<String> get difficulties {
+    return List<String>.generate(_Difficulty.values.length,
+        (index) => _Difficulty.values.elementAt(index).name);
+  }
+}
+
+enum _Difficulty { veryEasy, easy, intermediate, hard, veryHard }

lib/models/recipe.dart

@@ -1,3 +1,4 @@
+import 'difficulty.dart';
 import 'ingredient.dart';
 import 'steps.dart';
 
@@ -14,5 +15,3 @@ class Recipe {
     this.difficulty,
   });
 }
-
-enum Difficulty { veryEasy, easy, intermediate, hard, veryHard }

lib/pages/create_recipe_page.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
 
-import '../models/recipe.dart';
+import '../models/difficulty.dart';
 import '../widgets/difficulty_dropdown.dart';
 
 class CreateRecipe extends StatefulWidget {

lib/widgets/difficulty_dropdown.dart

@@ -1,15 +1,18 @@
 import 'package:flutter/material.dart';
 import 'package:rezepte/models/recipe.dart';
 
+import '../models/difficulty.dart';
+
 class DifficultyDropdown extends StatelessWidget {
   const DifficultyDropdown({super.key});
 
   @override
   Widget build(BuildContext context) {
-    List<DropdownMenuEntry> dropdownMenuEntryList = List.generate(
-        Difficulty.values.length,
-        (index) => _toDropdownMenuEntry(
-            index, Difficulty.values.elementAt(index).name));
+    List<DropdownMenuEntry> dropdownMenuEntryList = Difficulty.difficulties
+        .map(
+          (e) => _toDropdownMenuEntry(Difficulty.difficulties.indexOf(e), e),
+        )
+        .toList();
 
     return DropdownMenu(
       dropdownMenuEntries: dropdownMenuEntryList,