add a pizza size dependant field

pizza size is only required when the meal is dinner and the food pizza.

this introduces a 2nd level of dependant fields.
Meal -> Food -> Pizza size.

Here, we need to use `FormFactoryInterface::createNamedBuilder()` to get access to `addEventListener()`,
as that method is not available on `FormInterface`.

Author: bendavies

ux.symfony.com/composer.json

@@ -20,6 +20,7 @@
         "symfony/asset-mapper": "6.3.x-dev",
         "symfony/console": "6.3.*",
         "symfony/dotenv": "6.3.*",
+        "symfony/expression-language": "6.3.*",
         "symfony/flex": "^2",
         "symfony/form": "6.3.*",
         "symfony/framework-bundle": "6.3.x-dev",

ux.symfony.com/composer.lock

@@ -0,0 +1,19 @@
+<?php
+
+namespace App\Enum;
+
+enum PizzaSize: int
+{
+    case Small = 12;
+    case Medium = 14;
+    case Large = 16;
+
+    public function getReadable(): string
+    {
+        return match ($this) {
+            self::Small => '12 inch',
+            self::Medium => '14 inch',
+            self::Large => '16 inch',
+        };
+    }
+}

ux.symfony.com/src/Enum/PizzaSize.php

@@ -4,24 +4,30 @@
 
 use App\Enum\Food;
 use App\Enum\Meal;
+use App\Enum\PizzaSize;
 use App\Model\MealPlan;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\Extension\Core\Type\EnumType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\Form\FormEvent;
 use Symfony\Component\Form\FormEvents;
+use Symfony\Component\Form\FormFactoryInterface;
 use Symfony\Component\Form\FormInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
 class MealPlannerForm extends AbstractType
 {
+    private FormFactoryInterface $factory;
+
     /**
      * @var array<string, mixed>
      */
     private $dependencies = [];
 
     public function buildForm(FormBuilderInterface $builder, array $options)
     {
+        $this->factory = $builder->getFormFactory();
+
         $builder->add('meal', EnumType::class, [
             'class' => Meal::class,
             'choice_label' => fn (Meal $meal): string => $meal->getReadable(),
@@ -47,6 +53,7 @@ public function onPreSetData(FormEvent $event): void
         $data = $event->getData();
 
         $this->addFoodField($event->getForm(), $data?->getMeal());
+        $this->addPizzaSizeField($event->getForm(), $data?->getPizzaSize());
     }
 
     public function storeDependencies(FormEvent $event): void
@@ -62,16 +69,47 @@ public function onPostSubmitMeal(FormEvent $event): void
         );
     }
 
+    public function onPostSubmitFood(FormEvent $event): void
+    {
+        $this->addPizzaSizeField(
+            $event->getForm()->getParent(),
+            $this->dependencies['mainFood'],
+        );
+
+        $this->dependencies = [];
+    }
+
     public function addFoodField(FormInterface $form, ?Meal $meal): void
     {
-        $form->add('mainFood', EnumType::class, [
-            'class' => Food::class,
-            'placeholder' => null === $meal ? 'Select a meal first' : sprintf('What\'s for %s?', $meal->getReadable()),
-            'choices' => $meal?->getFoodChoices(),
-            'choice_label' => fn (Food $food): string => $food->getReadable(),
-            'disabled' => null === $meal,
-            // silence real-time "invalid" message when switching "meals"
-            'invalid_message' => false,
+        $mainFood = $this->factory
+            ->createNamedBuilder('mainFood', EnumType::class, $meal, [
+                'class' => Food::class,
+                'placeholder' => null === $meal ? 'Select a meal first' : sprintf('What\'s for %s?', $meal->getReadable()),
+                'choices' => $meal?->getFoodChoices(),
+                'choice_label' => fn (Food $food): string => $food->getReadable(),
+                'disabled' => null === $meal,
+                // silence real-time "invalid" message when switching "meals"
+                'invalid_message' => false,
+                'autocomplete' => true,
+                'auto_initialize' => false,
+            ])
+            ->addEventListener(FormEvents::POST_SUBMIT, [$this, 'storeDependencies'])
+            ->addEventListener(FormEvents::POST_SUBMIT, [$this, 'onPostSubmitFood']);
+
+        $form->add($mainFood->getForm());
+    }
+
+    public function addPizzaSizeField(FormInterface $form, ?Food $food): void
+    {
+        if (Food::Pizza !== $food) {
+            return;
+        }
+
+        $form->add('pizzaSize', EnumType::class, [
+            'class' => PizzaSize::class,
+            'placeholder' => 'What size pizza?',
+            'choice_label' => fn (PizzaSize $pizzaSize): string => $pizzaSize->getReadable(),
+            'required' => true,
             'autocomplete' => true,
         ]);
     }

ux.symfony.com/src/Form/MealPlannerForm.php

@@ -4,16 +4,25 @@
 
 use App\Enum\Food;
 use App\Enum\Meal;
-use Symfony\Component\Validator\Constraints\NotBlank;
+use App\Enum\PizzaSize;
+use Symfony\Component\Validator\Constraints as Assert;
 
 class MealPlan
 {
-    #[NotBlank]
+    #[Assert\NotNull]
     private ?Meal $meal = null;
 
-    #[NotBlank]
+    #[Assert\NotNull]
     private ?Food $mainFood = null;
 
+    #[Assert\When(
+        expression: 'this.getMainFood() === enum("App\\\Enum\\\Food::Pizza")',
+        constraints: [
+            new Assert\NotNull(message: 'Please select a Pizza Size.'),
+        ],
+    )]
+    private ?PizzaSize $pizzaSize = null;
+
     public function getMeal(): ?Meal
     {
         return $this->meal;
@@ -33,4 +42,14 @@ public function setMainFood(?Food $mainFood): void
     {
         $this->mainFood = $mainFood;
     }
+
+    public function getPizzaSize(): ?PizzaSize
+    {
+        return $this->pizzaSize;
+    }
+
+    public function setPizzaSize(?PizzaSize $pizzaSize): void
+    {
+        $this->pizzaSize = $pizzaSize;
+    }
 }

ux.symfony.com/src/Model/MealPlan.php

@@ -5,5 +5,8 @@
     {{ form_start(form) }}
         {{ form_row(form.meal) }}
         {{ form_row(form.mainFood) }}
+        {% if form.pizzaSize is defined %}
+            {{ form_row(form.pizzaSize) }}
+        {% endif %}
     {{ form_end(form) }}
 </div>