TArray Section 3 Lecture 94 UE 4.18.3

Unreal Courses Talk
#1

I just finished getting through the TArray lecture when I tried to run the code form the method GetTotalMassOfActorsOnPlate. The code compiled just fine but when I stepped on the plate it would cause the editor to crash.

Code used that was causing this issue:

for(auto* Actor : OverlappingActors)
{
	UE_LOG(LogTemp, Warning, TEXT("Actor %s is on me, ouch!", *Actor->GetName());
}

My debugging steps
I first tried to limit what was happening in the for loop and even if I did a simple log without any reference to the Actor in the list it would still crash when I stepped on the pressure plate.

I commented out the loop and the editor would now not crash so it had something to do with the loop and the TArray<AActor*>. So next I decided to try and see if there were any elements in the TArray once the PressurePlate->GetOverlappingActors(OUT OverlappingActors) method was called. I added this maco log output:

UE_LOG(LogTemp, Warning, TEXT("I found %d Actors"), OverlappingActors->Num());

Once this compiled this would produce a message every frame but the idea is that now I knew if there were items in the TArray. When nothing was in the TriggerVolume it would produce 0 items in the array which is expected. Once I stepped on the plate it would turn to 1 item in the array. Great we are finally getting somewhere. So I grabbed a chair and tossed into the TriggerVolume and viola now I was getting 2 items in the array while I was standing next to the chair. Once I left the trigger volume it still show 1 item in the array.

When now that I knew there were elements I tried one of my old tricks in programming. Always check for valid data before running a section of code. So here is the updated code I’ve added:

	PressurePlate->GetOverlappingActors(OUT OverlappingActors);
	if (OverlappingActors.Num() > 0)
	{
		for (auto* Actor : OverlappingActors)
		{
			TotalMass += Actor->FindComponentByClass<UPrimitiveComponent>()->GetMass();
		}
	}

Once I added the data validation check the code stopped crashing the engine. I did try and delete the project build files and directories but this didn’t stopped it from crashing. I hope this will help someone else taking this course who might have run into this same or similar issue.

Happy coding!
-LEde

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