Null Check

[Velcronator]

I’m probably jumping the gun here, and this question will be answered very soon. I thought I’d do this as a simple self-challenge.

At the moment if we press the 4 or 5 key we get a Null Reference error.

Is this a reasonable way to do the null reference check, and should be done here in the ActiveInventory.cs script? Thoughts?

    private void ChangeActiveWeapon()
    {
        if(ActiveWeapon.Instance.CurrentActiveWeapon != null)
        {
            Destroy(ActiveWeapon.Instance.CurrentActiveWeapon.gameObject);
        }

        if (!transform.GetChild(_activeSlotIndexNum).GetComponentInChildren<InventorySlot>())
        {
            ActiveWeapon.Instance.WeaponNull();
            return;
        }

        //Null question
        GameObject weaponToSpawn = transform?.GetChild(_activeSlotIndexNum)?.GetComponentInChildren<InventorySlot>()?.GetWeaponInfo()?.weaponPrefab;
        //Exit Change Active Weapon if no prefab was found. Stays on the previous Weapon
        if(weaponToSpawn == null) { return; }

        GameObject newWeapon = Instantiate(weaponToSpawn, ActiveWeapon.Instance.transform.position, Quaternion.identity);

        ActiveWeapon.Instance.transform.rotation = Quaternion.Euler(0f, 0f, 0f);

        newWeapon.transform.parent = ActiveWeapon.Instance.transform;

        ActiveWeapon.Instance.NewWeapon(newWeapon.GetComponent<MonoBehaviour>());
    }

[Stephen_Hubbard]

You’re right we’ll tackle it soon! I believe this specifically in the clean-up lecture at the end of the section if I recall. But later on, you’ll see I’ve tackled it in more or less the same way.

[Velcronator]

Great. Thanks Stephen

[bixarrio]

@Velcronator

GameObject weaponToSpawn = transform?.GetChild(_activeSlotIndexNum)?.GetComponentInChildren<InventorySlot>()?.GetWeaponInfo()?.weaponPrefab;

While this is usually fine, Unity does not want us to use the null-conditional operator here, so it’s probably best to do it the old way.

From the documentation for Unity’s Object (which transform inherits from):

This class doesn’t support the null-conditional operator ( ?. ) and the null-coalescing operator ( ?? ).

It may work in some cases, but there is no guarantee that it will always be the case, so be aware of that

[heckert]

I also solved this right away … like this:

        void ChangeActiveWeapon()
        {
          //...
           GameObject weaponToSpawn = invSlot.GetWeaponInfo()?.weaponPrefab;

            if (null != weaponToSpawn)
            {
              //...
            }
        }