Function ULevelStreaming::CreateInstance(class FString) unresolved external symbol when compiling

Development Programming & Scripting
1

Hi, when compiling the following code:

void ALevelGenCpp::AllocationMapParts()
{
	FString LevInstName;

	FLatentActionInfo LatentActionInfo;

	LatentActionInfo.CallbackTarget = this;
	LatentActionInfo.ExecutionFunction = "TestCall";
	LatentActionInfo.UUID = 123;
	LatentActionInfo.Linkage = 0;

	ULevelStreaming *pStreaming = UGameplayStatics::GetStreamingLevel(GEngine->GetWorld(), "dsfd")->CreateInstance("55");
	pStreaming->LevelTransform = FTransform();
	UGameplayStatics::LoadStreamLevel(GEngine->GetWorld(), "55", true, false, LatentActionInfo);
}

I get error:

LevelGenCpp.cpp.obj : error LNK2019: ������ �� ������������� ������� ������ "public: class ULevelStreaming * __cdecl ULevelStreaming::CreateInstance(class FString)" (?CreateInstance@ULevelStreaming@@QEAAPEAV1@VFString@@@Z) � ������� "public: void __cdecl ALevelGenCpp::AllocationMapParts(void)" (?AllocationMapParts@ALevelGenCpp@@QEAAXXZ)

PS: I found Question with the same problem:

2

Hey Deema_35-

The compiler doesn’t recognize the pStreaming pointer’s type. Adding an include statement for LevelStreaming.h should identify what pStreaming is to the compiler and solve the compile errors.

Cheers

Doug Wilson

3

This is not work, because this is not error compiler, this is error linker. It can not find external symbol.
I am publish error again because in last time I have problems with localization VS.

1>LevelGenCpp.cpp.obj : error LNK2019: unresolved external symbol “public: class ULevelStreaming * __cdecl ULevelStreaming::CreateInstance(class FString)” (?CreateInstance@ULevelStreaming@@QEAAPEAV1@VFString@@@Z) referenced in function “public: void __cdecl ALevelGenCpp::PlacedCustomLevelParts(void)” (?PlacedCustomLevelParts@ALevelGenCpp@@QEAAXXZ)
1>D:\Unreal Projects\TCofK\Binaries\Win64\UE4Editor-TCofK.dll : fatal error LNK1120: 1 unresolved externals

4

The ULevelStreaming class is marked as MinimalAPI in the source code which only exposes the bare minimum of that class to be called outside that class. If you are using a source build of the engine you can edit LevelStreaming.h to change the UCLASS specifier from MInimalAPI to EngineAPI.

5

I have the same issue. I would like to start with that I have tried changing line 78 of LevelStreaming.h from minimalAPI to EngineAPI, and the problem still persists I have also tried changing Line 79 to say class ENGINE_API ULevelStreaming : public UObject; and removed all the other calls to ENGINE_API. I have also tried adding a ENGINE_API on line 293 and none of these have worked. The code that causes the link error is simple because I’m trying to get it to build.

#include “LevelSpawnTest.h”
#include “Engine/LevelStreaming.h”

void LevelSpawnTest::CreateNewWorld(FString pName, ULevelStreaming* pLevelType, FTransform pTransform) {
pLevelType->CreateInstance(pName);
}

I know that this is an older question but if there is a fix it would greatly help, or if there is a better way to make it so that I can randomly generate a tower with X amount of floors loading each floor independently.