Tank Game Projectile randomly stopped working

[JDoe]

I tried to run the DamageTaken() function in the HealthComponent in lecture “Applying Damage 136” when I started to get a crash that was typical for referencing a null pointer. So I started commenting out code fragments until the game would stop crashing. I figured out that it was the reference to the static mesh component of BP_Projectile that was missing. When I look at BP_Projectile in the content browser, it clearly shows the Bullet Mesh

but when I open the full blueprint editor, the viewport section doesn’t show the projectile mesh. What’s more: I added the selection for the static mesh component using a UPROPERTY(EditDefaultsOnly, Category = “Combat”) in the C++ class. But when I look at the derived blueprint actor from my C++ class, that section doesn’t show up. The hierarchy of the components clearly shows that there is a static mesh component, but the UPROPERTY is invisible and cannot be set to anything and the mesh doesn’t appear in the viewport.

I didn’t have any fatal crashes before this and I always made sure to rebuild the entire project from VSCode after every lecture with the editor closed. I am baffled how this could even happen in the first place, but I am not really mad anymore since I’ve already made the experience that Unreal likes to randomly break things for some reason.

So my current strategy is to remake the BP_Projectile from the C++ Class and reset all the properties (if that will be possible then), which should be no issue, since all the code for those components to exist is specified in the C++ code of the AProjectile constructor.

Header file:

My question is:
How did this happen? Did I set some property incorrectly? Did I compile incorrectly? And also:
Do changes to the C++ class of AProjectile not get dynamically passed on to the derived BP_Projectile blueprint? If I add another component through C++ in Projectile.cpp, should that component not show up in the outliner of the derived BP_Projectile blueprint after compiling? How can it be that my C++ code is all there, I keep recompiling it, yet the StaticMeshComponent property seems to be missing from the BP_Blueprint and cannot be set? Is the broken blueprint preventing the updates in C++ from reaching the derived BP_blueprint somehow?

[DanM]

@JDoe

How did this happen?

Without knowing absolutely every step you did, it’s incredibly hard to even guess.

@JDoe

Do changes to the C++ class of AProjectile not get dynamically passed on to the derived BP_Projectile blueprint

It kind of depends as they get serialised. Adding members should be fine but modifying them is just going to change the defaults. Changing

int32 Value = 3;

to

int32 Value = 5;

isn’t going to affect existing blueprints or instances. This is why the binding of the delegate was done in BeginPlay instead of the constructor as the blueprint was already created.

@JDoe

How can it be that my C++ code is all there, I keep recompiling it, yet the StaticMeshComponent property seems to be missing from the BP_Blueprint and cannot be set?

It would be at this point I would throw the blueprint away and create a new one. Can’t really tell you why that happened as I’m not entirely sure.