LockerSubject.cs

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

namespace Ruccho.Utilities
{
    public class LockerSubject
    {
        public bool IsLocked => Keys.Count > 0;

        private List<object> Keys { get; } = new List<object>();
        private Action OnLocked { get; }
        private Action OnUnlocked { get; }


        public LockerSubject(Action onLocked, Action onUnlocked)
        {
            OnLocked = onLocked;
            OnUnlocked = onUnlocked;
        }

        public LockerSession Lock()
        {
            var session = new LockerSession(this);
            Lock(session);
            return session;
        }

        public void Lock(object key)
        {
            bool old = IsLocked;

            if (Keys.Contains(key))
            {
                Debug.LogWarning($"LockerSubject: This key ({key}) is already registered.");
            }
            else
            {
                Keys.Add(key);
            }

            if (old != IsLocked) OnLocked?.Invoke();
        }

        public void Unlock(object key)
        {
            bool old = IsLocked;

            if (!Keys.Contains(key))
            {
                Debug.LogWarning($"LockerSubject: This key ({key}) is not registered.");
            }
            else
            {
                Keys.Remove(key);
            }

            if (old != IsLocked) OnUnlocked?.Invoke();
        }
    }

    public class LockerSession : IDisposable
    {
        private LockerSubject subject;
        private bool isDisposed = false;

        public LockerSession(LockerSubject subject)
        {
            this.subject = subject;
        }

        public void Dispose()
        {
            if (isDisposed) return;
            isDisposed = true;
            subject.Unlock(this);
        }
    }
}

LockerSubjectSample.cs

using UnityEngine;

namespace Ruccho.Utilities
{
    public class LockerSubjectSample : MonoBehaviour
    {
        void Start()
        {
            Test();
        }

        private void Test()
        {
            var subject = new LockerSubject(OnLocked, OnUnlocked);

            Debug.Log("Lock by \"A\"");
            subject.Lock("A");
            
            //Output: LockerSubject has been locked.
            
            Debug.Log("Lock by \"B\"");
            subject.Lock("B");
            
            Debug.Log("Unlock by \"A\"");
            subject.Unlock("A");
            Debug.Log("Unlock by \"B\"");
            subject.Unlock("B");
            
            //Output: LockerSubject has been unlocked.
            
            Debug.Log("Lock with using statement");
            using (subject.Lock())
            {
                //Output: LockerSubject has been locked.
                
                Debug.Log("~~ in using statement ~~");
            }
            //Output: LockerSubject has been unlocked.
        }

        private void OnLocked() => Debug.Log("LockerSubject has been locked.");
        private void OnUnlocked() => Debug.Log("LockerSubject has been unlocked.");
    }
}