Unreal Engine: How Can I Create Ustaticmeshcomponent in a Loop?
I Am Trying to Create Multiple Ustaticmeshcomponent by Using for Loop but Unreal Engine Keeps Triggering Breakpoint on Createdefaultsubobject in Object. H(Not...
I am trying to create multiple UStaticMeshComponent by using for loop but Unreal Engine keeps triggering breakpoint on CreateDefaultSubobject in Object.h(Not in my code, it's from UE4 core API). When I'm creating a single component it's working fine. I am pretty new to UnrealEngine and C++ so I might be doing something dumb but please be easy on that:)
Thank you so much for your help.
Header
#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "FlowSphere.generated.h"
UCLASS()
class CPP_PRACTICE_3_API AFlowSphere : public AActor
{
GENERATED_BODY()
public:
// Sets default values for this actor's properties
AFlowSphere();
protected:
// Called when the game starts or when spawned
virtual void BeginPlay() override;
public:
// Called every frame
virtual void Tick(float DeltaTime) override;
private:
//UPROPERTY()
//TArray<UStaticMeshComponent*> StaticMeshComponents;
UStaticMeshComponent* test;
};
C++
#include "FlowSphere.h"
// Sets default values
AFlowSphere::AFlowSphere()
{
int32 amount = 100;
RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");
for (int32 i = 0; i < amount; i++) {
//WHEN I INCLUDE THE LINE BELOW, UE4 START MAKING BREAKPOINT
UStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("Sphere"));
item.AttachTo(this->RootComponent);
}
//THIS WORKS FINE
this->test = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("HELLO"));
PrimaryActorTick.bCanEverTick = true;
}
// Called when the game starts or when spawned
void AFlowSphere::BeginPlay()
{
Super::BeginPlay();
}
// Called every frame
void AFlowSphere::Tick(float DeltaTime)
{
Super::Tick(DeltaTime);
}
Where it triggering breakpoint on the Object.h from UE4 API
/**
* Create a component or subobject
* @param TReturnType class of return type, all overrides must be of this type
* @param SubobjectName name of the new component
* @param bTransient true if the component is being assigned to a transient property. This does not make the component itself transient, but does stop it from inheriting parent defaults
*/
template<class TReturnType>
TReturnType* CreateDefaultSubobject(FName SubobjectName, bool bTransient = false)
{
UClass* ReturnType = TReturnType::StaticClass();
return static_cast<TReturnType*>(CreateDefaultSubobject(SubobjectName, ReturnType, ReturnType, /*bIsRequired =*/ true, /*bIsAbstract =*/ false, bTransient));
}
2 Answers
You used the same name for two different calls to CreateDefaultSubobject.
I ran your code in a new UE4 C++ project and got the following error message:
Fatal error: [File:D:\Build++UE4\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp] [Line: 3755] Default subobject StaticMeshComponent Sphere already exists for FlowSphere /Script/MyProject.Default__FlowSphere.
Also, the code you posted didn't compile.
item.AttachTo(this->RootComponent);
should have been:
item->AttachTo(this->RootComponent);
and you also needed to include "Components/StaticMeshComponent.h". Here is the corrected code:
#include "FlowSphere.h"
#include "Components/StaticMeshComponent.h"
// Sets default values
AFlowSphere::AFlowSphere()
{
int32 amount = 100;
RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");
for (int32 i = 0; i < amount; i++) {
FName name = *FString::Printf(TEXT("Sphere %i"), i);
UStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(name);
item->AttachTo(this->RootComponent);
}
this->test = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("HELLO"));
PrimaryActorTick.bCanEverTick = true;
}
So I had to do the same thing recently and ran into a lot of issues but the two major things to fix are:
- use UInstancedStaticMesh instead of UStaticMesh.
- add a property to your static mesh.
Below is the correct code.
#include "FlowSphere.h"
#include "Components/StaticMeshComponent.h"
#include "UObject/ConstructorHelpers.h"
// Sets default values
AFlowSphere::AFlowSphere()
{
int32 amount = 100;
RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");
for (int32 i = 0; i < amount; i++) {
FName name = *FString::Printf(TEXT("Sphere %i"), i);
FName c_name = *FString::Printf(TEXT("ChildSceneComponent %i"), i);
UPROPERTY(EditAnywhere)
USceneComponent* ChildSceneComponent
= CreateDefaultSubobject<USceneComponent>(c_name);
// instead of the regular static mesh, create and instance static mesh object with name assigned
UInstancedStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(name);
item->RegisterComponent();
// assign property to mesh if not you'll get a static mesh null property error like i did
auto MeshAsset = ConstructorHelpers::FObjectFinder<UStaticMesh>(TEXT("StaticMesh'/Engine/BasicShapes/Sphere.Sphere'"));
if (MeshAsset.Object != nullptr)
{
item->SetStaticMesh(MeshAsset.Object);
}
item->SetFlags(RF_Transactional);
// add instance to actor level
this->AddInstanceComponent(item);
// make the scene component for the mesh to be visible
RootComponent = Root;
// attach mesh to the scene component of the actor in form of a Hierarchy
item->AttachToComponent(ChildSceneComponent, FAttachmentTransformRules::KeepWorldTransform, m_name);
ChildSceneComponent->AttachToComponent(Root, FAttachmentTransformRules::KeepWorldTransform, c_name);
// set mesh transform based on the ith position
FTransform t(FVector(250 * i, i, i));
// activate the new copy of the mesh
Mesh->AddInstance(t);
// Offset and scale the child scene from the root scene as a precaution
ChildSceneComponent->SetRelativeTransform(
FTransform(FRotator(0, 0, 0),
FVector(250 * i, i, i),
FVector(0.1f))
);
}
PrimaryActorTick.bCanEverTick = true;
}
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