I have a base class “item” in game. It has a static private pointer to “player” GameObject:
abstract public class Item : MonoBehaviour
{
// Keep single pointer across all Item classes.
static private GameObject _playerObj;
virtual protected void Start()
{
var player = GameManager.Instance.GetPlayerGameObj();
Debug.Log(player == null); // log1
Debug.Log(_playerObj == null); // log2
_playerObj ??= player;
Debug.Log(_playerObj == null); // log3
}
.....
}
After reloading scene, runtime error shows _playerObj is pointing to null. I printed logs and found some really weird behaviors:
- In the first run, everything is fine: When I spawn the first item, log1=false, log2=true, log3=false. For following items, all logs are false.
- After reload, for EVERY items spawned, log1=false, log2=true, log3=true.
I’m really having a headache here, since it looks like an issue of “??=” operator. log1=false means “player” is set, log2=true means _playerObj is null. “??=” should assign “player” to “_playerObj” since the left hand side is null, but yet log3 shows _playerObj is still null.
Then I replaced “??=” with：
if (_playerObj == null)
{
_playerObj = player;
}
And the problem is magically fixed.
I’ve read doc on “??=” but didn’t find anything suspicious: ?? and ??= operators - null-coalescing operators | Microsoft Learn
I have no idea if this is something with C# or Unity, or I just missed something since I’ve relatively new to those two. Any insights are appreciated. Thanks!