How to spawn a blueprint from C++?

Development Programming & Scripting
1

I have attempted to program some code that spawns a bullet above my pawn. However , when I run it , nothing happens. The header file contains:

TSubclassOf <class APlayerPawn> MyBulletBlueprint;

And inside the .cpp file, in the constructer there is:

static ConstructorHelpers::FObjectFinder<UBlueprint> BulletBlueprint(TEXT("Blueprint'/Content/Blueprints/BulletBP.BulletBP'"));
	if (BulletBlueprint.Object){
		MyBulletBlueprint = (UClass*)BulletBlueprint.Object->GeneratedClass;
	}

and the actual code that is meant to spawn the blueprint is:

UWorld* const World = GetWorld();
	if (World)
	{
		FActorSpawnParameters SpawnParams;
		SpawnParams.Instigator = this;
		World->SpawnActor<APlayerPawn>(MyBulletBlueprint, APlayerPawn::GetActorLocation() + FVector(0.0f,0.0f,BulletGap), APlayerPawn::GetActorRotation(), SpawnParams);
	}

What have I done wrong?

2

All thanks goto to Rama.

Paste this into a header file like your pre-compiled header. This will allow you to use it like below.

 template <typename ASpawnBP>
    FORCEINLINE ASpawnBP* SpawnBP(
    	UWorld* TheWorld,
    	UClass* TheBP,
    	const FVector& Loc,
    	const FRotator& Rot,
    	const bool bNoCollisionFail = true,
    	AActor* Owner = NULL,
    	APawn* Instigator = NULL
    	)
    {
    	if (!TheWorld) return NULL;
    	if (!TheBP) return NULL;
    	//~~~~~~~~~~~
    
    	FActorSpawnParameters SpawnInfo;
    	SpawnInfo.bNoCollisionFail = bNoCollisionFail;
    	SpawnInfo.Owner = Owner;
    	SpawnInfo.Instigator = Instigator;
    	SpawnInfo.bDeferConstruction = false;
    
    	return TheWorld->SpawnActor<ASpawnBP>(TheBP, Loc, Rot, SpawnInfo);
    }

This would go in some header like an aactor

UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = SpawningBP)
     UClass* BPSpawning;

And this would be how you use it

 const FVector  GenSpawnLoc(0.0f, 0.0f, 0.0f);
 const FRotator GenSpawnRot(0.0f, 0.0f, 0.0f);

For instance an AStaticMeshActor

AStaticMeshActor* SpawnedBP = SpawnBP<AStaticMeshActor>(GetWorld(), BPSpawning, GenSpawnLoc, GenSpawnRot);

or an AActor

AActor* SpawnedBP = SpawnBP<AActor>(GetWorld(), BPSpawning, GenSpawnLoc, GenSpawnRot);
3

That worked , thanks.

4

How to make it work from BlueprintFunctionLibrary (atleast in C++)?

Rama posted on wiki:
From a Static Library, in an actor class (for use of GetWorld()). SpawnLoc and SpawnRot are calculated by you based on your needs.

  AActorBaseClass* NewActor = UFunctionLibrary::SpawnBP(GetWorld(), TheActorBluePrint, SpawnLoc, SpawnRot);

No compile errors, but having function definition in BPFL.h and calling above line of code in some AMyActor.cpp doesn’t spawn anything.