Why is TActorIterator crashing UE?

Development Programming & Scripting
1

I have a single actor subclass, HUDManager, in my persistent level, and I’m trying to give the player a reference to that actor so he can send and receive events:

AHUDManager* HUDManager;

	for (TActorIterator<AHUDManager> ActorItr(GetWorld()); ActorItr; ++ActorItr)
	{
		HUDManager = *ActorItr;
	}

This looks right to me based on rama’s tutorial, but UE crashes every time I try to run this- what am I doing wrong?

Crash log, as requested:

Unknown exception - code 00000001 (first/second chance not available)

"Assertion failed: CurrentWorld [File:c:\program files (x86)\epic games\4.8\engine\source\runtime\engine\public\EngineUtils.h] [Line: 183]
"

UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:355]
UE4Editor_Projectname_834!FActorIteratorBase::FActorIteratorBase() [c:\program files (x86)\epic games\4.8\engine\source\runtime\engine\public\engineutils.h:185]
UE4Editor_Projectname_834!AMCharacter::AMCharacter() [c:\users\username\documents\unreal projects\projectname\source\projectname\mcharacter.cpp:72]
UE4Editor_HotReload!FHotReloadClassReinstancer::ReconstructClassDefaultObject() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreloadclassreinstancer.cpp:195]
UE4Editor_HotReload!FHotReloadClassReinstancer::RecreateCDOAndSetupOldClassReinstancing() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreloadclassreinstancer.cpp:232]
UE4Editor_HotReload!FHotReloadClassReinstancer::FHotReloadClassReinstancer() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreloadclassreinstancer.cpp:293]
UE4Editor_HotReload!FHotReloadClassReinstancer::Create() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreloadclassreinstancer.h:114]
UE4Editor_HotReload!FHotReloadModule::ReinstanceClass() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreload.cpp:873]
UE4Editor_CoreUObject!UClassReplaceHotReloadClasses() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:662]
UE4Editor_CoreUObject!ProcessNewlyLoadedUObjects() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:822]
UE4Editor_CoreUObject!TBaseStaticDelegateInstance::ExecuteIfSafe() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:921]
UE4Editor_Core!TBaseMulticastDelegate::Broadcast() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\public\delegates\delegatesignatureimpl_variadics.inl:1031]
UE4Editor_Core!FModuleManager::LoadModuleWithFailureReason() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\modules\modulemanager.cpp:431]
UE4Editor_Core!FModuleManager::LoadModule() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\modules\modulemanager.cpp:303]
UE4Editor_HotReload!FHotReloadModule::DoHotReloadInternal() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreload.cpp:679]
UE4Editor_HotReload!FHotReloadModule::DoHotReloadCallback() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreload.cpp:620]
UE4Editor_HotReload!TBaseRawMethodDelegateInstance<0,FHotReloadModule,TTypeWrapper cdecl(bool,enum ECompilationResult::Type),TArray,TArray,FOutputDevice & ptr64>::Execute() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:492]
UE4Editor_HotReload!TBaseRawMethodDelegateInstance<0,FHotReloadModule,void cdecl(bool,enum ECompilationResult::Type),TArray,TArray,FOutputDevice & ptr64>::ExecuteIfSafe() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:582]
UE4Editor_HotReload!FHotReloadModule::CheckForFinishedModuleDLLCompile() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreload.cpp:1486]
UE4Editor_HotReload!FHotReloadModule::Tick() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\developer\hotreload\private\hotreload.cpp:433]
UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\editorengine.cpp:952]
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\unrealedengine.cpp:366]
UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launchengineloop.cpp:2359]
UE4Editor!GuardedMain() [d:\buildfarm\buildmachine++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:200]

2

Paste here stack trace from this crash.

3

Sure, I edited the main post and added it, mcharacter(72) is the line quoted above where the for loop starts.

4

Oh, hot reloading.

From where are you calling this piece of code? Constructor of some class?

5

Yep, this is from MCharacter’s constructor, and MCharacter is a subclass of ACharacter.

6

I think it is not safe to calling Iterators in constructors during hot reload, GetWorld() is probably returning nullptr especially for default objects:)

Try secure it with:

if(GetWorld())
{
 // run da iterator
}

or move iterator code to:

virtual void AActor::OnConstruction(const FTransform& Transform) {}

or check if object is default object

if (HasAnyFlags(RF_ClassDefaultObject) == false)
{
 //run da iterator
}
7

That is excellent advice, and does the trick perfectly- if you wanna repost as an answer, I’ll accept it real quick. Thank you so much!!

Sidenote: this is probably the fifth time in a week or two I’ve confused myself by forgetting that GetWorld() can return null :slight_smile:

8

Sure, converted to answer;0