Polymorphism and casting

Fruit Class

using UnityEngine;
using System.Collections;

public class Fruit 
{
    public Fruit()
    {
        Debug.Log("1st Fruit Constructor Called");
    }

    public void Chop()
    {
        Debug.Log("The fruit has been chopped.");        
    }

    public void SayHello()
    {
        Debug.Log("Hello, I am a fruit.");
    }
}

Apple Class

using UnityEngine;
using System.Collections;

public class Apple : Fruit 
{
    public Apple()
    {
        Debug.Log("1st Apple Constructor Called");
    }

    //Apple has its own version of Chop() and SayHello(). 
    //When running the scripts, notice when Fruit's version
    //of these methods are called and when Apple's version
    //of these methods are called.
    //In this example, the "new" keyword is used to supress
    //warnings from Unity while not overriding the methods
    //in the Apple class.
    public new void Chop()
    {
        Debug.Log("The apple has been chopped.");        
    }

    public new void SayHello()
    {
        Debug.Log("Hello, I am an apple.");
    }
}

FruitSalad Class

using UnityEngine;
using System.Collections;

public class FruitSalad : MonoBehaviour
{
    void Start () 
    {
        //Notice here how the variable "myFruit" is of type
        //Fruit but is being assigned a reference to an Apple. This
        //works because of Polymorphism. Since an Apple is a Fruit,
        //this works just fine. While the Apple reference is stored
        //in a Fruit variable, it can only be used like a Fruit
        Fruit myFruit = new Apple();

        myFruit.SayHello();
        myFruit.Chop();

        //This is called downcasting. The variable "myFruit" which is 
        //of type Fruit, actually contains a reference to an Apple. Therefore,
        //it can safely be turned back into an Apple variable. This allows
        //it to be used like an Apple, where before it could only be used
        //like a Fruit.
        Apple myApple = (Apple)myFruit;

        myApple.SayHello();
        myApple.Chop();    
    }
}