Polymorphism
Tutorial
Intermediate
5 Mins
Overview
Overview
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1.
Polymorphism
Summary
How to use Polymorphism, Upcasting, and Downcasting to create powerful and dynamic functionality between inherited classes.
Topics we'll cover
Language
English
Recommended Unity Versions
4.3 and Above
Tutorial
Polymorphism
1.
Polymorphism

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(); } }