Values in Custom Inspector get lost when unselecting object. Why?

Questions & Answers
1

I created a custom inspector where I assign various objects and values but if I unselect the object the values are lost.

[CustomEditor(typeof(WeaponControl))]
[System.Serializable]
public class WeaponInspector : Editor {
    public WeaponControl _myTarget;

    public AudioClip audioClip;

    public GameObject parentGO;
    [SerializeField]
    public GameObject Character;
    public GameObject weaponPrefab;
    public GameObject LeftHand;
    private GameObject RightHand;
    private Vector3 copyPosition;
    
    public static void SetupScene()
    {
        EditorApplication.NewEmptyScene();       
    }

    private void OnEnable()
    {
        Debug.Log("OnEnable was called...");
        _myTarget = (WeaponControl)target;
    }

    private void OnDisable()
    {
        Debug.Log("OnDisable was called...");
    }

    private void OnDestroy()
    {
        Debug.Log("OnDestroy was called...");
    }
    public override void OnInspectorGUI()
    {    
        //DrawDefaultInspector();
        DrawWeaponBuilder();
    }

    private void DrawWeaponBuilder()
    {
        //Weapon type
        _myTarget.weaponType = (WeaponManager.WeaponType)EditorGUILayout.EnumPopup("Type of weapon: ", _myTarget.weaponType);

        EditorGUILayout.BeginVertical("box");
        
        //Weapon prefab
        weaponPrefab = (GameObject)EditorGUILayout.ObjectField("Weapon prefab: ", weaponPrefab, typeof(GameObject), false);
        if (weaponPrefab != null&& RightHand!=null)
        {
            if (GUILayout.Button("Add Weapon to scene"))
            {
                GameObject weapon= (GameObject) Instantiate(weaponPrefab, RightHand.transform.position, RightHand.transform.rotation);
                weapon.transform.parent = parentGO.transform;
            }
        }
        
        //Audioclip, must be added to AudioSource component
        audioClip = (AudioClip)EditorGUILayout.ObjectField("Audio Clip", audioClip, typeof(AudioClip), false);
        if (audioClip != null)
        {
            if (GUILayout.Button("Add Audio Source component"))
            {
                parentGO.AddComponent<AudioSource>();
                parentGO.GetComponent<AudioSource>().clip = audioClip;
            }
        }

        //Position target forr left hand
        _myTarget.HandPosition = (GameObject)EditorGUILayout.ObjectField("Hand Position: ", _myTarget.HandPosition, typeof(GameObject), false);

        //Prefab for ParticleSystem
        _myTarget.bulletPrefab = (GameObject)EditorGUILayout.ObjectField("Bullet Particles: ", _myTarget.bulletPrefab, typeof(GameObject), false);

        //Where the bullets spawn
        _myTarget.bulletSpawn = (Transform)EditorGUILayout.ObjectField("Bullet Spawn: ", _myTarget.bulletSpawn, typeof(Transform), false);
        EditorGUILayout.EndVertical();

        // Max ammo for this weapon
        _myTarget.MaxAmmo = EditorGUILayout.IntField("Max # of rounds: ", _myTarget.MaxAmmo);

        //Max # of clips the player can carry
        _myTarget.MaxClipAmmo = EditorGUILayout.IntField("Max # clips: ", _myTarget.MaxClipAmmo);

       
        if (LeftHand != null)
        {
            _myTarget.EquipPosition = EditorGUILayout.Vector3Field("Equip position: ", LeftHand.transform.position);
        }
        else
        {
            _myTarget.EquipPosition = EditorGUILayout.Vector3Field("Equip position: ",new Vector3(0,0,0));
        }
        if (weaponPrefab != null)
        {
            if (GUILayout.Button("Copy Transform"))
            {
                CopyTransform(weaponPrefab);
                }
        }
        if (weaponPrefab != null)
        {
            if (GUILayout.Button("Past Transform"))
            {
                PastTransform(weaponPrefab);
            }
        }
        EditorGUILayout.Space();
        EditorGUILayout.Space();
        EditorGUILayout.Space();
        EditorGUILayout.Space();
        Character = (GameObject)EditorGUILayout.ObjectField("Character: ", Character, typeof(GameObject), false);

        if(Character!= null)
        {
            if(GUILayout.Button("Add Character"))
            {
                Instantiate(Character, Vector3.zero, Quaternion.identity);
            }
        }
        if (Character != null)
        {
            RightHand = (GameObject)EditorGUILayout.ObjectField("RightHand: ", RightHand, typeof(GameObject), true);
        }
        if (Character != null)
        {
            LeftHand = (GameObject)EditorGUILayout.ObjectField("LeftHand: ", LeftHand, typeof(GameObject), true);
        }
    }

    private void CopyTransform(GameObject go)
    {
        copyPosition = go.transform.localPosition;
       
    }

    private void PastTransform(GameObject go)
    {
        weaponPrefab.transform.localPosition= copyPosition;
    }
}
2

A custom editor is just a temporal object. It’s just an editor. When you select your object, the inspector will create the proper custom editor for each component / object that is selected. When you deselect the object those editor instances are no longer needed.

If you have simple configurations (bool, int, string, …) you can use EditorPrefs. For everything more complicated like asset references you would need to store those in an actual asset. A ScriptableObject is commonly used for this. Unity does a similar thing for most project settings.

If you just need to store some references temporarily you can use static variables in your editor. However those get lost as well when scripts are recompiled or the playmode changes.

So the only way to make such things survive is to store them in “something” that is actually serialized (prefab, ScriptableObject asset or an object in the scene.)