UAkMarkerCallbackInfo, UAkDurationCallbackInfo, UAkMIDIEventCallbackInfo casting problem in C++

Question

Hi, I've been challenging with callback function lately in C++. So far everything seemed okay, my code looks like the below. The problem is, whenever I try to cast UAkCallbackInfo* to UAkMarkerCallbackInfo, UAkDurationCallbackInfo or UAkMIDIEventCallbackInfo, it gives a linker error like this:

2>FireBase.cpp.obj : error LNK2019: unresolved external symbol "private: static class UClass * __cdecl UAkMarkerCallbackInfo::GetPrivateStaticClass(void)" (?GetPrivateStaticClass@UAkMarkerCallbackInfo@@CAPEAVUClass@@XZ) referenced in function "public: void __cdecl AFireBase::CallbackFunc(enum EAkCallbackType,class UAkCallbackInfo *)" (?CallbackFunc@AFireBase@@QEAAXW4EAkCallbackType@@PEAVUAkCallbackInfo@@@Z)
2>E:\0_PROJECTS\TheVillage\Binaries\Win64\UnrealEditor-TheVillage.dll : fatal error LNK1120: 1 unresolved externals

The thing weird looking is, I can cast UAkCallbackInfo to UAkEventCallbackInfo, which is parent class for these three callbackinfo's I can't cast. I don't know where did I make it wrong, and having that linker error seems ridiculous.
- "AkAudio" is in the Build.cs
- I include AkGameplayStatics.h on the headers (other functions are working well, no problem at any events or rtpc stuff)

 

FireBase.h

#include "CoreMinimal.h"
#include "../Plugins/Wwise/Source/AkAudio/Classes/AkGameplayStatics.h"
#include "Particles/ParticleSystemComponent.h"
#include "GameFramework/Actor.h"
#include "FireBase.generated.h"

UCLASS()
class THEVILLAGE_API AFireBase : public AActor
{
    GENERATED_BODY()

    FOnAkPostEventCallback BindCallback;

public:    
    // Sets default values for this actor's properties
    AFireBase();

    UFUNCTION()
    void CallbackFunc(EAkCallbackType CallbackType, UAkCallbackInfo* CallbackInfo);
protected:
    // Called when the game starts or when spawned
    virtual void BeginPlay() override;

public:    
    // Called every frame
    //virtual void Tick(float DeltaTime) override;

    UPROPERTY(EditAnywhere,BlueprintReadWrite,Category="FX")
    UParticleSystemComponent* BlueFireFX;

};

 

FireBase.cpp

#include "FireBase.h"

void AFireBase::BeginPlay()
{
    Super::BeginPlay();

    BindCallback.BindUFunction(this, "CallbackFunc");

    TArray<FAkExternalSourceInfo> nullSources;

    UAkGameplayStatics::PostEvent(nullptr, this, int32(EAkCallbackType::Marker), BindCallback, nullSources, false, (FString)("FireBase"));

    BlueFireFX->Deactivate();
    
}

void AFireBase::CallbackFunc(EAkCallbackType CallbackType, UAkCallbackInfo* CallbackInfo)
{
    UAkMarkerCallbackInfo* CBInfo = Cast<UAkMarkerCallbackInfo>(CallbackInfo);
}

 

Also, it doesn't give an error if I just declare UAkMarkerCallbackInfo* to anywhere, but if I use the class in Cast<>, it pops that error I mentioned above.

Comments

I'm having the same type of error:

  unresolved external symbol "private: static class UClass * __cdecl UAkDurationCallbackInfo::GetPrivateStaticClass(void)" (?GetPrivateStaticClass@UAkDurationCallbackInfo@@CAPEAVUClass@@XZ) referenced in function "public: void __cdecl AAkComponentPool::OnAkEventCallback(enum EAkCallbackType,class UAkCallbackInfo *,class UAkComponent *)" (?OnAkEventCallback@AAkComponentPool@@QEAAXW4EAkCallbackType@@PEAVUAkCallbackInfo@@PEAVUAkComponent@@@Z)

When I try to:

UAkDurationCallbackInfo* DurationCallbackInfo = Cast<UAkDurationCallbackInfo>(CallbackInfo);

Were you able to solve this?

Answer 1

For anyone that is looking for an answer to this problem, the issue both of these commenters are running into is due to UAkMarkerCallbackInfo not having the AKAUDIO_API macro after the class specifier. That macro allows the class to be exported out of the plugin and used in the rest of your project. To solve the unresolved externals error just add AKAUDIO_API, the declaration should look like this then -
class AKAUDIO_API UAkMarkerCallbackInfo : public UAkEventCallbackInfo

Doing that will allow you to cast to UAkMarkerCallbackInfo outside of the Wwise plugin.