Pointer to incomplete class type is not allowed Unreal Engine 4.26

Question

I try to implement the pawn navigation to the player in my game. When I tried that in BP site, it worked perfectly, but I try to transform that in C++ code. And I got a kind of wird error. Befor this I faced another error but I find the NavigationSystem was changed a bit in my ue version, but I figured out problem by changing to UNavigationSystemV1. It might be interfering with my class?

NavPath pointer it gave me the error.

Here is the error list:

> Error (active)    E0393   pointer to incomplete class type is not allowed 37
> Error (active)    E0393   pointer to incomplete class type is not allowed 40
> Error C2027   use of undefined type 'UNavigationPath'37
> Error C2027   use of undefined type 'UNavigationPath' 40

Here is the part of problematic code:

FVector ASTrackerBot::GetNextPathPoint()
{
ACharacter* PlayerPawn =  UGameplayStatics::GetPlayerCharacter(this, 0);

UNavigationPath* NavPath = UNavigationSystemV1::FindPathToActorSynchronously(this, 
GetActorLocation(), PlayerPawn);

if (NavPath->PathPoints.Num() > 1)
{

    return NavPath->PathPoints[1];
}


return GetActorLocation();

}

Here is my entire private cpp file:

#include "AI/STrackerBot.h"
#include "Components/StaticMeshComponent.h"
#include "GameFramework/Character.h"
#include "Kismet/GameplayStatics.h"
#include "Runtime\NavigationSystem\Public\NavigationSystem.h"
#include "Runtime/Engine/Classes/Components/InputComponent.h"


// Sets default values
ASTrackerBot::ASTrackerBot()
{
    // 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;

    MeshComp = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("MeshComp"));
    MeshComp->SetCanEverAffectNavigation(false);
    RootComponent = MeshComp;
}

// Called when the game starts or when spawned
void ASTrackerBot::BeginPlay()
{
    Super::BeginPlay();
    
}

FVector ASTrackerBot::GetNextPathPoint()
{
    // parcurgere drum pana la locatia playerului
    ACharacter* PlayerPawn =  UGameplayStatics::GetPlayerCharacter(this, 0);
    
    UNavigationPath* NavPath = UNavigationSystemV1::FindPathToActorSynchronously(this, GetActorLocation(), PlayerPawn);

    if (NavPath->PathPoints.Num() > 1)
    {
        // Return next point in the path
        return NavPath->PathPoints[1];
    }

    // nu a reusti sa gaseasca drumul
    return GetActorLocation();
}

// Called every frame
void ASTrackerBot::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

}

And here is my header file:

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Pawn.h"
#include "STrackerBot.generated.h"

UCLASS()
class GAME_API ASTrackerBot : public APawn
{
    GENERATED_BODY()

public:
    // Sets default values for this pawn's properties
    ASTrackerBot();

protected:
    // Called when the game starts or when spawned
    virtual void BeginPlay() override;

    UPROPERTY(VisibleAnywhere, Category = "Components")
    UStaticMeshComponent* MeshComp;

    FVector GetNextPathPoint();

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

};

Answer 1

You may also need to add the NavigationSystem module to your Project.Build.cs file in the PublicDependencyModuleNames array.