OnActorBeginOvelap.AddDynamic this is null

Development Programming & Scripting C++
, ,
1

Im trying to bind a function to a box trigger that the level script has a reference to.

in the .h

ALevelTrigger* LevelTrigger;

UFUNCTION()
void BeginOverlap(AActor* OverlappedActor, AActor* OtherActor);

begin overlap implementation

void ALevelOneScriptActor::BeginOverlap(AActor* OverlappedActor, AActor* OtherActor)
{
	UE_LOG(LogTemp, Warning, TEXT("OverlappedActor: %s"), *OverlappedActor->GetName());
	UE_LOG(LogTemp, Warning, TEXT("OtherActor: %s"), *OtherActor->GetName());
}

in BeginPlay in level script cpp

LevelTrigger->OnActorBeginOverlap.AddDynamic(this, &ALevelOneScriptActor::BeginOverlap);

This causes a crash and error which points me to this line

check(DelegateOwner->IsValidLowLevelFast(false)); // Most likely the delegate is trying to be used on the stack, in an object it wasn't defined for, or for a class member with a different name than it was defined for. It is only valid for a sparse delegate to be used for the exact class/property name it is defined with.

This seems to mean i cant use ALevelOneScriptActor as a delegate although this seems like a pretty standard thing to do so i dont know what im doing wrong.

Thanks in advance!

2

Without diving too deep here, you might be binding too early. Your level’s BeginPlay might get called before LevelTrigger is spawned (just guessing). Try to find a different place to bind. It should be somewhere you know the LevelTrigger is actually spawned.

You could test this by just adding a delay to your bind:

FTimerHandle TempTimer;
GetWorld()->GetTimerManager().SetTimer
(
	TempTimer,
	[=]() 
    { 
       LevelTrigger->OnActorBeginOverlap.AddDynamic(this, &ALevelOneScriptActor::BeginOverlap);
    },
	1.0f,
	false
);
3

Assuming that you know that this is not null when calling AddDynamic() (you could add an assert, or log, or check with a breakpoint,) the next thing to make sure is that your LevelTrigger is tagged with a UPROPERTY() so that GC knows about it.

UPROPERTY()
ALevelTrigger *LevelTrigger;
4

Cheers guys, the timer didnt fix it but made it a lot easier to see whats going on. Think the UPROPERTY() ultimately fixed it in the end, Thanks!