.. include:: ../_header.rst

Prefab code generation
~~~~~~~~~~~~~~~~~~~~~~

A prefab_ file is a scene and is compiled into JavaScript (or TypeScript) code. A regular scene file is compiled into a class that extends the `Phaser.Scene <https://photonstorm.github.io/phaser3-docs/Phaser.Scene.html>`_ class. It is a scene after all. However, the prefab_ file is compiled into a custom object class.

The prefab_ class generated by the |SceneCompiler|_ extends a game object class, like an `Image <image-object.html>`_, a `BitmapText <bitmap-text-object.html>`_, etc... or `another prefab class <prefab-variant.html>`_.

This is the code generated after compile the **Dragon** prefab:

.. code::

    class Dragon extends Phaser.GameObjects.Image {
        
        constructor(scene, x, y, texture, frame) {
            super(scene, x ?? 100, y ?? 100, texture || "dragon", frame ?? "dragon/flamming_00");

            this.scaleX = 0.7;
            this.scaleY = 0.7;        
        }       
    }
    
    
Note the prefab_ class extends the `Phaser.GameObjects.Image <https://photonstorm.github.io/phaser3-docs/Phaser.GameObjects.Image.html>`_ class, because the `prefab object <prefab-object.html>`_ is an `Image`_.

The constructor of the **Dragon** class has the same arguments of the `Image`_ class, but by default, it uses the texture set in the `prefab object`_. Also, in the body of the constructor, are set the properties modified in the `prefab object`_:

.. code::

    this.scaleX = 0.7;
    this.scaleY = 0.7;  


When the |SceneCompiler|_ compiles a regular scene file, the |PrefabInstances|_ in it are generated as instances of the prefab_ class:

.. code::

    class Level extends Phaser.Scene {
    
        constructor() {
            super("Level");            
        }
        
        create() {
            ...

            // create the instance of the Dragon prefab class
            const dragon = new Dragon(this, 190, 120);
            // add the instance to the display list
            this.add.existing(dragon);
            // modify the 'angle' property of the instance
            dragon.angle = -30;            
            ...
        }
    }

Also, the prefab_ class can be instantiated manually by you, at any time in your game. It is just a custom object class that looks like if you write it by hand.