Constants and switch-case Statement

Constants (const)

Constants are values that never change once set. Used in games to define fixed values like max health, max level, base speed, etc.

public class Player : MonoBehaviour
{
    // Game configuration constants
    const int MAX_HP = 100;           // Max health
    const int MAX_LEVEL = 50;         // Max level
    const float BASE_MOVE_SPEED = 5f;  // Base movement speed
    const int STARTING_GOLD = 100;     // Starting gold
    
    public int currentHp = MAX_HP;
    public int currentLevel = 1;
}

• Why use them?

  • Use meaningful names in code (hp > 0 is less clear than hp > DEAD_HP)
  • Change values in one place when needed (use MAX_HP constant instead of writing 100 everywhere)
  • Prevent accidental value changes (const cannot be modified)
  • Avoid magic numbers (meaningless numbers)

• Difference from variables

  • Variable: int hp = 100; (can change later with hp = 50;)
  • Constant: const int MAX_HP = 100; (cannot change later, MAX_HP = 50; causes error!)

Input.GetKeyDown()

A Unity function to detect keyboard input. Used to receive player input and control the game.

void Update()
{
    // Jump when spacebar is pressed
    if (Input.GetKeyDown(KeyCode.Space))
    {
        Jump();
    }
    
    // Skip dialogue when Enter is pressed
    if (Input.GetKeyDown(KeyCode.Return))
    {
        SkipDialogue();
    }
}

• Common key codes

  • KeyCode.Space: Spacebar (jump, skip dialogue)
  • KeyCode.Return or KeyCode.Enter: Enter key (confirm, advance dialogue)
  • KeyCode.A, KeyCode.B, KeyCode.C: Alphabet keys (skill shortcuts)
  • KeyCode.LeftArrow, KeyCode.RightArrow: Arrow keys (movement)
  • KeyCode.Alpha1, KeyCode.Alpha2: Number keys 1, 2 (item use)

• GetKeyDown vs GetKey vs GetKeyUp

  • GetKeyDown: true only once when key is pressed (jump, attack, etc.)
  • GetKey: true continuously while key is held (movement, running, etc.)
  • GetKeyUp: true only once when key is released (special actions)

Game usage example:

void Update()
{
    // Movement (while holding)
    if (Input.GetKey(KeyCode.W))
    {
        MoveForward();
    }
    
    // Jump (on press)
    if (Input.GetKeyDown(KeyCode.Space))
    {
        Jump();
    }
    
    // Use skill (number key)
    if (Input.GetKeyDown(KeyCode.Alpha1))
    {
        UseSkill(1);
    }
}

switch-case Statement

A clean way to handle multiple cases. Much more readable than using if-else if multiple times.

public class Player : MonoBehaviour
{
    public int playerLevel = 1;
    
    void Start()
    {
        // Give different rewards based on level
        switch (playerLevel)
        {
            case 1:
                GiveReward("Beginner Weapon");
                break;
            case 5:
                GiveReward("Intermediate Armor");
                break;
            case 10:
                GiveReward("Advanced Ring");
                break;
            default:
                Debug.Log("No reward");
                break;
        }
    }
    
    void GiveReward(string itemName)
    {
        Debug.Log("Obtained " + itemName + "!");
    }
}

• Comparison with if-else if

  • if-else if: useful for complex conditions (hp > 0 && hp < 50 - range comparison)
  • switch-case: cleaner for comparing specific values (exact value comparison)

• Keyword meanings

  • switch (variable): which variable to compare
  • case value:: execute if variable equals this value
  • break;: end here and exit (required! without it, next case also executes)
  • default:: execute if none of the above cases match

• Game development practical examples

Example 1: Different effects based on item type

public enum ItemType { Weapon, Armor, Potion, Key }

void UseItem(ItemType itemType)
{
    switch (itemType)
    {
        case ItemType.Weapon:
            EquipWeapon();
            break;
        case ItemType.Armor:
            EquipArmor();
            break;
        case ItemType.Potion:
            RestoreHealth();
            break;
        case ItemType.Key:
            UnlockDoor();
            break;
    }
}

Example 2: Different actions based on game state

public enum GameState { Menu, Playing, Paused, GameOver }

void UpdateGameState(GameState state)
{
    switch (state)
    {
        case GameState.Menu:
            ShowMainMenu();
            break;
        case GameState.Playing:
            StartGameplay();
            break;
        case GameState.Paused:
            PauseGame();
            break;
        case GameState.GameOver:
            ShowGameOverScreen();
            break;
    }
}

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