How to cast a parent actor to a sub actor

Development Programming & Scripting
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1

hi.
I would like to ask a question.
i have a actor “ABaseSoldier”.it has a sub actor “APikemenSoldier”.
i want to cast “ABaseSoldier” actor to “APikemenSoldier” actor.
this is my code:

ABaseSoldier* BaseSoldier= GetWorld()->SpawnActor<ABaseSoldier>();
/*
 * Dothing
*/
TSubClass<ABaseSoldier > SoldierClass = GetSoldierClass();
// How to cast BaseSoldier to APikemenSoldier  actor?
BaseSolider = Cast<SoldierClass >();//Is error
// Is it theoretically possible to change the class of an actor that has already spawned?
2

It’s not possible to change the class of an already spawned actor.
You have to spawn the actor already as the type you want.

If you do that you can use it as its type or as one of its parent types.

TSubClass<ABaseSoldier > SoldierClass = GetSoldierClass();

// This will spawn whatever type SoldierClass is
ABaseSoldier* BaseSoldier = GetWorld()->SpawnActor<ABaseSoldier>(SoldierClass);

// This will give you BaseSoldier as APikemenSoldier or a nullptr if SoldierClass was not a APikemenSoldier 
APikemenSoldier*  PikemenSoldier = Cast<APikemenSoldier>(BaseSoldier);

you could also spawn a APikemenSoldier directly and use it as base soldier

ABaseSoldier* BaseSoldier = GetWorld()->SpawnActor<APikemenSoldier>();
3

thank you,Can I use TSubClass or UClass* for Cast()?

I need get different UClass* from "GetSoldierClass() " function.then Cast to this UClass*.
Here’s an example:

TSubClass<ABaseSoldier > SoldierClass = GetSoldierClass();
// The SoldierClass may be a APikemanSolider , or it may be a ASwordsmanSolider.
ABaseSoldier  Solider = Cast<SoldierClass >(BaseSoldier);
4

Have GetSoldierClass() be a function inside of an interface (eg. ISoldier).

Have all soldiers implement the interface ISoldier.
Then you can have GetSoldierClass() return a specific class in each variant
Each solder type presents it own class through the same command

The interface is like a contract that guarantees that the classes have an implementation of it’s functions.

No casting is then required.

5

what’s the actual thing you want to do?
As 3dRaven points out you might not need a cast

If you have a class of ABaseSoldier you can add a virtual function to it and do whatever you want with it

.h

UCLASS(Blueprintable)
class ABaseSoldier : public AActor
{
	GENERATED_BODY()

public:
	UFUNCTION(BlueprintCallable, BlueprintNativeEvent)
	void Attack();
};

UCLASS(Blueprintable)
class APikemenSoldier : public ABaseSoldier
{
	GENERATED_BODY()

public:
	virtual void Attack_Implementation() override;
};

UCLASS(Blueprintable)
class ASwordSoldier : public ABaseSoldier
{
	GENERATED_BODY()

public:
	virtual void Attack_Implementation() override;
};

.cpp

void ABaseSoldier::Attack_Implementation()
{
}

void APikemenSoldier::Attack_Implementation()
{
	UE_LOG(LogTemp, Warning, TEXT("Pike Attack"))
}

void ASwordSoldier::Attack_Implementation()

{
	UE_LOG(LogTemp, Warning, TEXT("Sword Attack"))
}

Then you can just call attack on the base soldier and the more specific version can do whatever they want.

If you want to cast you can do this
ABaseSoldier* SomeSoldierAsBaseSoldier;

if (APikemenSoldier* Pikemen = Cast<APikemenSoldier>(SomeSoldierAsBaseSoldier))
{
   // do what you want with Pikemen
}
else if (ASwordSoldier* SwordSoldier= Cast<ASwordSoldier>(SomeSoldierAsBaseSoldier))
{
   // do what you want with SwordSoldier
}

You can always try casting and if it is not of that class it will return nullptr