Fire a new becoming event for the become feature to allow hooking into the transformation process

Author: tonysm

readme.md

@@ -239,6 +239,14 @@ The `become()` method will return a new instance of the specified child model wi
 
 This is also useful when you're using observers or callbacks, since the specific child model's behavior will be triggered after the transition.
 
+A new model event is fired when a model is _becoming_ another type, you may listen to it like so:
+
+```php
+ShippedOrder::becoming(function ($shippedOrder) {
+    // Do something before the model is saved...
+});
+```
+
 ## Laravel Nova Support
 
 If you want to use share parent Nova resources with child models, you may register the following provider at the end of the boot method of your NovaServiceProvider:

src/HasChildren.php

@@ -20,6 +20,16 @@ trait HasChildren
      */
     protected $hasChildren = true;
 
+    /**
+     * Register a becoming model event with the dispatcher.
+     *
+     * @param  \Illuminate\Events\QueuedClosure|callable|array|class-string  $callback
+     */
+    public static function becoming($callback): void
+    {
+        static::registerModelEvent('becoming', $callback);
+    }
+
     /**
      * Register a model event with the dispatcher.
      *
@@ -268,6 +278,8 @@ public function become($class)
             $instance->setConnection($this->getConnectionName());
 
             $instance->setRelations($this->relations);
+
+            $instance->fireModelEvent('becoming', false);
         });
     }
 

tests/Features/ModelsCanBecomeOtherTypesTest.php

@@ -2,6 +2,7 @@
 
 namespace Parental\Tests\Features;
 
+use Illuminate\Support\Facades\Event;
 use Parental\Tests\Models\Car;
 use Parental\Tests\Models\ClawHammer;
 use Parental\Tests\Models\Mallet;
@@ -103,4 +104,31 @@ public function come_calls_model_events_on_specified_model(): void
 
         $this->assertTrue($carEventCalled);
     }
+
+    /** @test */
+    public function fires_becoming_model_event(): void
+    {
+        $becomingEventCalledCount = 0;
+
+        Event::listen('eloquent.becoming: ' . Car::class, function () use (&$becomingEventCalledCount) {
+            $becomingEventCalledCount++;
+        });
+
+        Car::becoming(function () use (&$becomingEventCalledCount) {
+            $becomingEventCalledCount++;
+        });
+
+        $vehicle = Vehicle::create(['type' => 'truck']);
+
+        $this->assertEquals(0, $becomingEventCalledCount);
+
+        $car = $vehicle->become(Car::class);
+        $car->save();
+
+        $this->assertInstanceOf(Car::class, $car);
+        $this->assertEquals('car', $car->type);
+        $this->assertEquals($vehicle->id, $car->id);
+
+        $this->assertEquals(2, $becomingEventCalledCount);
+    }
 }