added willpopscope

lib/pages/create_recipe_page.dart

@@ -16,10 +16,18 @@ class CreateRecipe extends StatefulWidget {
 class _CreateRecipeState extends State<CreateRecipe> {
   late RecipeProvider recipe;
 
+  @override
+  void dispose() {
+    super.dispose();
+    recipe.clearRecipe(silent: true);
+  }
+
   @override
   Widget build(BuildContext context) {
     recipe = Provider.of<RecipeProvider>(context);
-    return Scaffold(
+    return WillPopScope(
+      onWillPop: _onWillPop,
+      child: Scaffold(
         appBar: AppBar(
           title: const Text('Create Recipe'),
         ),
@@ -60,6 +68,7 @@ class _CreateRecipeState extends State<CreateRecipe> {
             ),
           ),
         ),
+      ),
     );
   }
 
@@ -102,4 +111,29 @@ class _CreateRecipeState extends State<CreateRecipe> {
       ),
     );
   }
+
+  Future<bool> _onWillPop() {
+    if (recipe.isEmpty) {
+      return Future<bool>(
+        () {
+          return true;
+        },
+      );
+    }
+    return showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Leave the page?'),
+        content: const Text('Progress will be lost.'),
+        actions: [
+          TextButton(
+              onPressed: () => Navigator.of(context).pop(false),
+              child: const Text('cancel')),
+          TextButton(
+              onPressed: () => Navigator.of(context).pop(true),
+              child: const Text('leave')),
+        ],
+      ),
+    ).then((value) => value ?? false);
+  }
 }

lib/services/providers/recipe_provider.dart

@@ -12,14 +12,28 @@ class RecipeProvider extends ChangeNotifier implements Recipe {
   final List<IngredientListEntry> _ingredients = [];
   final List<CookingStep> _steps = [];
 
-  void clearRecipe() {
+  void clearRecipe({silent = false}) {
     _title = '';
     _description = '';
     _difficulty = null;
     _ingredients.clear();
     _steps.clear();
+    if (!silent) {
       notifyListeners();
     }
+  }
+
+  bool get isEmpty {
+    return _title.isEmpty &&
+        _description.isEmpty &&
+        _difficulty == null &&
+        _ingredients.isEmpty &&
+        steps.isEmpty;
+  }
+
+  bool get isNotEmpty {
+    return !isEmpty;
+  }
 
   @override
   String get description => _description;