Unity MonoBehaviour ECS

World.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

/// <summary>
/// Enumerable component cache with methods for querying components based on their types.
/// </summary>
class World : IEnumerable<MonoBehaviour>
{
    public static readonly World Default = new();

    readonly Dictionary<Type, HashSet<MonoBehaviour>> cache = new();

    public IEnumerator<MonoBehaviour> GetEnumerator() =>
        cache.SelectMany(entry => entry.Value).Distinct().GetEnumerator();

    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    public event Action<MonoBehaviour> Added;
    public event Action<MonoBehaviour> Removed;

    public bool Add(MonoBehaviour component)
    {
        var added = false;
        if (component && !component.destroyCancellationToken.IsCancellationRequested)
        {
            foreach (var key in GetKeys(component))
            {
                if (!cache.TryGetValue(key, out var components))
                {
                    components = cache[key] = new();
                }

                if (components.Add(component))
                {
                    added = true;
                }
            }

            if (added)
            {
                var registration = component.destroyCancellationToken.Register(() => Remove(component));
                Removed += OnComponentRemoved;

                void OnComponentRemoved(MonoBehaviour removedComponent)
                {
                    if (component == removedComponent)
                    {
                        Removed -= OnComponentRemoved;
                        registration.Dispose();
                    }
                }

                Added?.Invoke(component);
            }
        }

        return added;
    }

    public bool Remove(MonoBehaviour component)
    {
        var removed = false;
        if (component)
        {
            foreach (var key in GetKeys(component))
            {
                if (cache[key].Remove(component))
                {
                    removed = true;
                    if (cache[key].Count == 0)
                    {
                        cache.Remove(key);
                    }
                }
            }

            if (removed)
            {
                Removed?.Invoke(component);
            }
        }

        return removed;
    }

    public void Clear()
    {
        var components = Removed != null ? this.ToList() : null;
        cache.Clear();
        components?.ForEach(Removed);
    }

    static IEnumerable<Type> GetKeys(MonoBehaviour component)
    {
        var type = component.GetType();
        while (type != typeof(MonoBehaviour))
        {
            yield return type;
            foreach (var interfaceType in type.GetInterfaces())
            {
                yield return interfaceType;
            }

            type = type.BaseType;
        }
    }

    public IEnumerable<T> Query<T>(bool includeDisabled = false)
        where T : class =>
        cache.TryGetValue(typeof(T), out var components)
            ? components.Where(component => includeDisabled || component.enabled).Cast<T>()
            : Enumerable.Empty<T>();

    public IEnumerable<(T1, T2)> Query<T1, T2>(bool includeDisabled = false)
        where T1 : class
        where T2 : class =>
        from x in Query<T1>(includeDisabled)
        join y in Query<T2>(includeDisabled) on (x as MonoBehaviour).gameObject equals (y as MonoBehaviour).gameObject
        select (x, y);

    public IEnumerable<(T1, T2, T3)> Query<T1, T2, T3>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class =>
        from xs in Query<T1, T2>(includeDisabled)
        join y in Query<T3>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, y);

    public IEnumerable<(T1, T2, T3, T4)> Query<T1, T2, T3, T4>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class =>
        from xs in Query<T1, T2, T3>(includeDisabled)
        join y in Query<T4>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, y);

    public IEnumerable<(T1, T2, T3, T4, T5)> Query<T1, T2, T3, T4, T5>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class =>
        from xs in Query<T1, T2, T3, T4>(includeDisabled)
        join y in Query<T5>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6)> Query<T1, T2, T3, T4, T5, T6>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class =>
        from xs in Query<T1, T2, T3, T4, T5>(includeDisabled)
        join y in Query<T6>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7)> Query<T1, T2, T3, T4, T5, T6, T7>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6>(includeDisabled)
        join y in Query<T7>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7, T8)> Query<T1, T2, T3, T4, T5, T6, T7, T8>(
        bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class
        where T8 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6, T7>(includeDisabled)
        join y in Query<T8>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, xs.Item7, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7, T8, T9)> Query<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
        bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class
        where T8 : class
        where T9 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6, T7, T8>(includeDisabled)
        join y in Query<T9>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, xs.Item7, xs.Item8, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)> Query<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
        bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class
        where T8 : class
        where T9 : class
        where T10 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6, T7, T8, T9>(includeDisabled)
        join y in Query<T10>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, xs.Item7, xs.Item8, xs.Item9, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)> Query<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10,
        T11>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class
        where T8 : class
        where T9 : class
        where T10 : class
        where T11 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(includeDisabled)
        join y in Query<T11>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, xs.Item7, xs.Item8, xs.Item9, xs.Item10, y);

    public IEnumerable<(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12)> Query<T1, T2, T3, T4, T5, T6, T7, T8, T9,
        T10, T11, T12>(bool includeDisabled = false)
        where T1 : class
        where T2 : class
        where T3 : class
        where T4 : class
        where T5 : class
        where T6 : class
        where T7 : class
        where T8 : class
        where T9 : class
        where T10 : class
        where T11 : class
        where T12 : class =>
        from xs in Query<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(includeDisabled)
        join y in Query<T12>(includeDisabled) on (xs.Item1 as MonoBehaviour).gameObject equals (y as MonoBehaviour)
            .gameObject
        select (xs.Item1, xs.Item2, xs.Item3, xs.Item4, xs.Item5, xs.Item6, xs.Item7, xs.Item8, xs.Item9, xs.Item10,
            xs.Item11, y);
}