Multi-Tag System

Authored by Kyle
Shared 08-09-2019

The Multi-Tag system leverages Odin's awesome Enum inspectors to allow you to easily tag a gameobject with many tags and then easily check for them via code. It is intended as a full replacement for Unity's "tag" system.

Usage

First define your "flags" and a MonoBehaviour you can attach to a gameobject.

using System;

[Flags]
public enum GameFlag
{
    None = 0,
    Player = 1 << 0,
    Enemy = 1 << 1,
    Pickup = 1 << 2,
    Bullet = 1 << 3,
    SplashDamage = 1 << 4,
    Health = 1 << 5,
    UI = 1 << 6
}

public class GameFlags : FlagsBehaviour<GameFlag> {}

Then you can attach this component to any gameobject and tick any that are applicable. You can then easily query for these flags to see if they are set on the gameobject using the extension methods.

public class ExampleClass : MonoBehaviour
{
    void OnCollisionEnter(Collision collision)
    {
        if (collision.HasFlag(GameFlag.Player | GameFlag.Pickup))
            this.AddFlag(GameFlag.Health);
    }
}

Implementation

FlagsBehaviour.cs

using System;
using UnityEngine;
using Sirenix.OdinInspector;

public interface IFlagsBehaviour<in T> where T : Enum
{
	bool HasFlag(T tag);
	void AddFlag(T tag);
	void RemoveFlag(T tag);
}

[HideMonoScript]
public abstract class FlagsBehaviour<T> : MonoBehaviour, IFlagsBehaviour<T> where T : Enum
{
	[SerializeField, HideInInspector]
	private T flags;

	[ShowInInspector, ShowIf("IsFlags"), HideLabel, EnumToggleButtons]
	public T Flags
	{
		get => flags;
		set => flags = value;
	}

	[ShowInInspector, HideIf("IsFlags"), HideLabel]
	private T Enum {
		get => Flags;
		set => Flags = value;
	}
	
	private bool IsFlags()
	{
		return typeof(T).IsDefined(typeof(FlagsAttribute), false);
	}

	public bool HasFlag(T flag)
	{
		return Flags.Has(flag);
	}
	
	public void AddFlag(T flag)
	{
		if (!HasFlag(flag)) Flags = Flags.Add<T>(flag);
	}
	
	public void RemoveFlag(T flag)
	{
		Flags = Flags.Remove<T>(flag);
	}
}

	public static class FlagsExtensions
{
	public static bool Has(this Enum self, Enum value)
	{
		try
		{
			return ((int)(object)self & (int)(object)value) == (int)(object)value;
		} 
		catch {
			return false;
		}
	}
	
	public static T Add<T>(this Enum self, Enum value) where T : Enum
	{
		try {
			return (T)(object)((int)(object)self | (int)(object)value);
		}
		catch(Exception ex) {
			throw new ArgumentException($"Could not append value from enumerated type '{typeof(T).Name}'.", ex);
		}    
	}

	public static T Remove<T>(this Enum self, Enum value) where T : Enum
	{
		try {
			return (T)(object)((int)(object)self & ~(int)(object)value);
		}
		catch (Exception ex) {
			throw new ArgumentException($"Could not remove value from enumerated type '{typeof(T).Name}'.", ex);
		}  
	}
	
	private static bool TryGetComponent<T>(this GameObject self, out IFlagsBehaviour<T> comp) where T : Enum
	{
		comp = self.GetComponent<IFlagsBehaviour<T>>();
		return (comp != null);
	}
	
	public static bool HasFlag<T> (this GameObject self, T flag) where T : Enum
	{
		return self.TryGetComponent(out IFlagsBehaviour<T> comp) && comp.HasFlag(flag);
	}
	
	public static void AddFlag<T> (this GameObject self, T flag) where T : Enum
	{
		if (self.TryGetComponent(out IFlagsBehaviour<T> comp)) comp.AddFlag(flag);
	}
	
	public static void RemoveFlag<T> (this GameObject self, T flag) where T : Enum
	{
		if (self.TryGetComponent(out IFlagsBehaviour<T> comp)) comp.RemoveFlag(flag);
	}
	
	private static bool TryGetComponent<T>(this Component self, out IFlagsBehaviour<T> comp) where T : Enum
	{
		comp = self.GetComponent<IFlagsBehaviour<T>>();
		return (comp != null);
	}
	
	public static bool HasFlag<T> (this Component self, T flag) where T : Enum
	{
		return self.TryGetComponent(out IFlagsBehaviour<T> comp) && comp.HasFlag(flag);
	}
	
	public static void AddFlag<T> (this Component self, T flag) where T : Enum
	{
		if (self.TryGetComponent(out IFlagsBehaviour<T> comp)) comp.AddFlag(flag);
	}
	
	public static void RemoveFlag<T> (this Component self, T flag) where T : Enum
	{
		if (self.TryGetComponent(out IFlagsBehaviour<T> comp)) comp.RemoveFlag(flag);
	}
}