Can't set pointer to derived type

Development Programming & Scripting
1

I’m making a test pawn class, and creating a component inside.
In the header file I put:

UPROPERTY(EditAnywhere)
USceneComponent* mySceneComponent;

and in the cpp:

AToonCarPawn::AToonCarPawn()
{
 	// Set this pawn to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;
	RootComponent = CreateDefaultSubobject<USceneComponent>(TEXT("RootComponent"));
	mySceneComponent = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("OurVisibleComponent"));

}

But i get the error :a value of type “UStaticMeshComponent *” cannot be assigned to an entity of type “USceneComponent *”

Doesn’t UStaticMeshComponent inherit USceneComponent? Am I misunderstanding something? I am perplexed.

2

Just to clarify, that’s not ALL that’s in those files. I just included the relevant snippets, and didn’t realize it would put line numbers like that. Let me know if I’m leaving out anything important.

3

Hi Zachfm,

you must use the exact class type for every member that are flagged as UPROPERTY, otherwise the Blueprint magic won’t work.

This is inherent to the way UE4 macro work: UPROPERTY will parse the next line and generate blueprint access (read/write…) functions according to the class.

Hope it helps,

Cø

4

Is that true in all cases, or only for properties which are flagged as accessible to Blueprint?

5

It looks like it’s only for UPROPERTY, the error must come for the UBT

6

What Co said is not true. You can assign any subclass of a variable type to the variable and the UPROPERTY will still function.

Have you tried casting the result of the component creation to USceneComponent* ?

7

I tried an explicit static cast and it said there was “no known conversion”

8

Thanks for your answer, Co

I was following this little tutorial when I did this: https://docs.unrealengine.com/latest/INT/Programming/Tutorials/PlayerInput/1/index.html

It looks like they do exactly this in the third step of the tutorial. Maybe I’m missing a setting somewhere or some nuance that’s allowing them to do this? Is there any difference between their code and mine that i’m not realizing?

9

You can try this (but it’s ugly):

mySceneComponent = Cast<USceneComponent>(CreateDefaultSubobject<UStaticMeshComponent>(TEXT("OurVisibleComponent")));
10

I tried the exact code you have above and it compiled and runs fine.
This was as a member variable with parent class UActorComponent;
Perhaps it needs a clean + build so the generated file is recreated? The only other thing that comes to mind is it’s somehow picking up a override, perhaps with a default template parameter?
Mac10.11.2,Xcode7.2,Unreal 4.10.2