Enums in the Inspector

Part of the Game Architecture in Unity section of Coddy's Unity journey. Lesson 20 of 64.

An enum field shows in the Inspector as a dropdown, which makes it a handy way to set up objects that share one script. One Pickup prefab serves for coins, hearts and shields: each copy in the level gets its kind from the dropdown, and the script switches on it:

public enum PickupKind { Coin, Heart, Shield }

public class Pickup : MonoBehaviour
{
    public PickupKind kind;
    public int amount = 1;

    void OnTriggerEnter(Collider other)
    {
        if (!other.TryGetComponent(out PlayerStats stats)) return;
        switch (kind)
        {
            case PickupKind.Coin: stats.coins += amount; break;
            case PickupKind.Heart: stats.hp += amount; break;
            case PickupKind.Shield: stats.shielded = true; break;
        }
        Destroy(gameObject);
    }
}

The scene saves each choice as the value's number: Coin is 0, Heart 1, Shield 2. Adding a value at the end is safe. Inserting one at the front, as in { Gem, Coin, Heart, Shield }, shifts every number, and every pickup in every scene changes kind. Renaming a value is safe, since its number stays the same. Writing the numbers out, Coin = 0, Heart = 1, Shield = 2, lets you reorder the names later without moving any saved choice.

A [System.Flags] enum holds several values at once. Its dropdown has a tick per value, plus Nothing and Everything. Each value needs a bit of its own, so the numbers are powers of two:

[System.Flags]
public enum Element { None = 0, Fire = 1, Ice = 2, Poison = 4 }

public Element immuneTo;   // ticked in the Inspector: Fire and Poison

public void Hit(int damage, Element element)
{
    if (immuneTo.HasFlag(element)) return;
    hp -= damage;
}

| combines values: Element.Fire | Element.Poison is 5. HasFlag(x) is true when every value in x is set, and ToString() lists the values that are set, as Fire, Poison.

Challenge

Easy

Let a door need several keycards and the ring hold several.

In KeyRing.cs, put [System.Flags] above Access and number it None = 0, Red = 1, Blue = 2, Green = 4.
Add(Access card) keeps the cards already there: cards |= card;.
Opens(Access needs) returns true only when the ring holds every card in needs.

Press Play and pick up both cards: the Vault opens. Then Check.

Try it yourself

using UnityEngine;

public enum Access { None, Red, Blue, Green }

public class KeyRing : MonoBehaviour
{
    public Access cards;

    public void Add(Access card)
    {
        // put the card on the ring, keeping the cards already there
    }

    public bool Opens(Access needs)
    {
        // true when the ring holds every card in needs
        return false;
    }
}