SceneReference.cs

using System;
using UnityEngine;
using Object = UnityEngine.Object;
using UnityEditor;
using UnityEditor.SceneManagement;

namespace SceneManagement
{
    [Serializable]
    public class SceneReference : ISerializationCallbackReceiver
    {
        [SerializeField] private Object sceneAsset;

        private string scenePath = string.Empty;

        private bool IsValidSceneAsset
        {
            get
            {
                if (!sceneAsset)
                    return false;

                return sceneAsset is SceneAsset;
            }
        }

        public string SceneName => sceneAsset.name;

        public string ScenePath
        {
            get => GetScenePathFromAsset();
            set
            {
                scenePath = value;
                sceneAsset = GetSceneAssetFromPath();
            }
        }

        public static implicit operator string(SceneReference sceneReference) => sceneReference.ScenePath;
        public void OnBeforeSerialize() => HandleBeforeSerialize();
        public void OnAfterDeserialize() => EditorApplication.update += HandleAfterDeserialize;
        private SceneAsset GetSceneAssetFromPath() => string.IsNullOrEmpty(scenePath) ? null : AssetDatabase.LoadAssetAtPath<SceneAsset>(scenePath);
        private string GetScenePathFromAsset() => sceneAsset == null ? string.Empty : AssetDatabase.GetAssetPath(sceneAsset);

        private void HandleBeforeSerialize()
        {
            if (IsValidSceneAsset == false && string.IsNullOrEmpty(scenePath) == false)
            {
                sceneAsset = GetSceneAssetFromPath();

                if (sceneAsset == null)
                    scenePath = string.Empty;

                EditorSceneManager.MarkAllScenesDirty();
            }
            else
            {
                scenePath = GetScenePathFromAsset();
            }
        }

        private void HandleAfterDeserialize()
        {
            EditorApplication.update -= HandleAfterDeserialize;

            if (IsValidSceneAsset)
                return;

            if (string.IsNullOrEmpty(scenePath))
                return;

            sceneAsset = GetSceneAssetFromPath();

            if (!sceneAsset)
                scenePath = string.Empty;

            if (!Application.isPlaying)
                EditorSceneManager.MarkAllScenesDirty();
        }
    }

#if UNITY_EDITOR
    [CustomPropertyDrawer(typeof(SceneReference))]
    public class SceneReferenceDrawer : PropertyDrawer
    {
        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
        {
            return EditorGUIUtility.singleLineHeight;
        }

        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            SerializedProperty sceneProp = property.FindPropertyRelative("sceneAsset");
            label = new GUIContent("Scene to Load");
            Rect pos = EditorGUI.PrefixLabel(position, label);
            EditorGUI.PropertyField(pos, sceneProp, GUIContent.none);
        }
    }
#endif
}