I didnt understand the Class tutorial

Unity Engine
1

What does a Class ‘do’?
Is the script itself the ‘Class’? If not provide example, which is class and which is script?
What is the purpose of the class?

I have seen the Class tutorial 3 times and I still dont get it…

2

When you declare a class, you write a blueprint of an object.

You have to see it that way, the class is the blueprint the computer will use to build an object.

Imagine you want a car. You can’t just snap your finger and bam… A car is made. You have to describe it first. Color, size, wheels, engine, door, etc… and most importantly, how it behave. If I press the pedals, what does it do?

So once you got that blueprint, you would give it to a engineer and he would build it for you. In this context, you give that blueprint to the computer, and it gives you a car - an instance.

So this is a blueprint - a class;

public class Car
{
    public Color color;
}

And this creates the car - an instance;

Car myCar = new Car();

In the case of Unity, the editor sees a file - a .cs, .js or .boo file - as being a “script”. This is a somewhat accepted non-sense, because in the end, the file contains a class. In other editor, a “script” would be a self-contain file that contains code interpreted at runtime. However, in Unity, those “scripts” are compiled and run as normal managed code.
On top, a file may contains multiple class, and a class can also contain other class.

So to keep it simple, let’s just assume that a “script” for Unity is a file that contains a MonoBehaviour.

3

Excellent starter description @LightStriker_1

@DarkEcho , once the Car object has been created by instantiating the “new Car()”, you will be able to do things with it. Here is a Car class in further detail…

class Car {

  public var numWheels : int = 4;     // externally accessible
  private var bodyColor : Color;      // available only to this instance of this object

  // Constructor, when this car is instantiated, this is "Main", use this to set up some stuff.
  public function Car ()
  {
    SayHello("Hello world, I am a car!");
    // note: when you get a handle on these classes, look at coroutines
  }

  // this method is publicly accessible, dynamically change its bodyColor variable
  public function SetColor (c : Color)
  {
    bodyColor = c;
  }

  // this method is only available to this object
  private function SayHello (s : String)
  {
    Debug.Log(s);
  }
}

Note the public and private member variables and methods (functions). After the car has been created, you can adjust things about it.

var myCar : Car = new Car();  // notice different syntax in JS
myCar.numWheels = 3;    // now a 3-wheeler!
myCar.SetColor(myRGBcolor); // assign a body color
myCar.SayHello("Trying to say Hello!");  // this one will bomb because it is a private method!!!

If you intend to use C#, here is a great “simplified” write-up on classes:

For JS, read this:

But keep in mind UnityScript is not really JavaScript but this example is still relevant.

4

So the “Script” is the file itself and the file contains the “Class” of how to perform Functions/Variables or make a car? Correct?

And the purpose of the class is just to make a car, I.e the Class is the engineer to make this car? Correct?

5
  1. Yes, in this example, you would name your file (script) Car.js or Car.cs.
  2. You are the engineer ;), Car() is the car.
6

Class = blueprint
You = designer who draw a blueprint
Computer = engineer who construct an object using a blueprint
Script = files containing classes

1 Like
7

I would disagree and strongly suggest disregarding anything to do with ECMAScript (web JavaScript).

8

Oh so Class is just a set of instrcutions and thats it.
Also I understand a script can have more than 1 Class.

9

Instructions (methods) and properties (fields). Car can roll, but a car also have a color.

10

True, I just couldn’t find anything similar for UnityScript. Just looked for something super simple so OP could get his head around the subject matter: properties, methods, inheritance. I will find something better. Maybe you know of a good example?

This is a much more accurate description of the relationship.