A Class is a group of related Variables and Functions. It allows your game to know what something is and what it can do.

• Summary
• Variable Basics
  • Standard Types
  • Unity Types
  • Others
  • Access
• Function Basics
  • Standard
  • With a Parameter
  • Returns a Type
• Examples
• Class vs Unity Component
• Notes

Summary

A Class is a group of related Variables and Functions, known as Members. It allows your game to know what something is and what it can do.

• Variable
  • Holds data of a certain Type (text, number, true/false, other class, etc)
  • Examples: Age, Color, Weight
• Function
  • Executes an action. Makes something happen.
  • Examples: Jump(), Move()

Just like high school, mathematics class contains all the information about mathematics. Mathematics doesn’t contain any information about history or art.

A Class can be added to a GameObject as a Component.

An Object (or Instance) is a version/copy of a Class that exists “in the world” (in memory). Think of a Class as the recipe, and the Object/Instance as the cake. Many Instances can be created from the same Class.

Variable Basics

Variables can hold different types of data.

Standard Types

int    number;      // Holds a single whole number
float  decimalNum;  // Holds a single decimal number
string text;        // Holds text
bool   trueOrFalse; // Holds a true or false value

Unity Types

GameObject go;           // Holds a GameObject
Transform  t;            // Holds a GameObject's Transform component
Vector2    twoNumbers;   // Holds two numbers (x, y)
Vector3    threeNumbers; // Holds three numbers (x, y, z)

Others

GameObject[]                   array;      // Holds many GameObjects
List<Transform>                list;       // Holds many Transform components
Dictionary<string, GameObject> dictionary; // Holds many GameObjects found using a string ID
CustomClass                    myClass;    // Holds a custom class

Access

Variables can be public or private (and more).

• Public means it is accessible from other Classes.
• Private means it is only accessible from inside its own Class.

Function Basics

Functions make something happen when executed. They are sometimes called Methods.

Standard

void Jump()
{
    Debug.Log("Jumped");
}

With a Parameter

void Jump(int howHigh)
{
    Debug.Log("Jumped " + howHigh + " metres into the air");
}

Returns a Type

bool IsAlive()
{
    if (_currentHealth > 0)
    {
        return true;
    }
    else
    {
        return false;
    }
}

// Can be used like so:
void TestFunction()
{
    if (IsAlive())
    {
        // Alive
    }
    else
    {
        // Dead
    }
}

Examples

• http://pastebin.com/cnSUVVac

Class vs Unity Component

• Instantiating is different for both
  • Class - ClassName varName = new ClassName();
  • Component - ClassName varName = gameObject.AddComponent<ClassName>();, or click-drag the component onto the GameObject.

Notes

• Classes should be a group of related things. In school, a history class does not teach mathematics. They focus on one topic.
• https://forum.unity.com/threads/component-based-weapon-system.204999/
• Self - Make differences between classes/structs clear
• http://www.tutorialsteacher.com/csharp/csharp-class
• http://www.tutorialsteacher.com/csharp/csharp-data-types
• C# Programming Yellow Book by Rob Miles