programming

Unity 3D Game Engine – JavaScript – Overriding

Overriding è una pratica che consente di sovrascrivere un metodo della classe padre con un metodo della classe figlia.

Fruit Class

#pragma strict

public class Fruit 
{
    public function Fruit ()
    {
        Debug.Log("1st Fruit Constructor Called");
    }
    
    //Overriding members happens automatically in 
    //Javascript and doesn't require additional keywords
    public function Chop ()
    {
        Debug.Log("The fruit has been chopped.");     
    }
    
    public function SayHello ()
    {
        Debug.Log("Hello, I am a fruit.");
    }
}

Apple Class

#pragma strict

public class Apple extends Fruit 
{
    public function Apple ()
    {
        Debug.Log("1st Apple Constructor Called");
    }
    
    //Overriding members happens automatically in 
    //Javascript and doesn't require additional keywords
    public function Chop ()
    {
        super.Chop();
        Debug.Log("The apple has been chopped.");     
    }
    
    public function SayHello ()
    {
        super.SayHello();
        Debug.Log("Hello, I am an apple.");
    }
}

FruitSalad Class

#pragma strict

function Start () 
{
    var myApple = new Apple();
    
    //Notice that the Apple version of the methods
    //override the fruit versions. Also notice that
    //since the Apple versions call the Fruit version with
    //the "base" keyword, both are called.
    myApple.SayHello();
    myApple.Chop(); 
    
    //Overriding is also useful in a polymorphic situation.
    //Since the methods of the Fruit class are "virtual" and
    //the methods of the Apple class are "override", when we 
    //upcast an Apple into a Fruit, the Apple version of the 
    //Methods are used.
    var myFruit = new Apple();
    myFruit.SayHello();
    myFruit.Chop();
}

Come funziona?

1. Fruit Class
– una classe pubblica Fruit con le funzioni Fruit() – Chop() – SayHello()

2. Apple Class
– classe figlia di Fruit con le funzioni
– Apple()
– Chop()-> super.Chop()
– SayHello()-> super.SayHello()

3. FruitSalad Class
– la funzione Start() si avvia la caricamento dello script
– richiama Apple().SayHello() e Apple().Chop() -> che vanno in ovverride su Fruit().SayHello() e Fruit().Chop()