GetWorldTimerManager in derived class which is not in UWorld

Development Programming & Scripting
1

Unless I’m severely mistaken, you don’t actually have an instance of “AMeleeCombatSystem”. I’m not even sure how this compiles, as “meleeSystem” seems to be a local variable in your constructor.

I would suggest the following:

In your Player’s Header:

UPROPERTY()
AMeleeCombatSystem* MeleeCombatSystem

In your Player’s cpp:

ABaseCharacter::ABaseCharacter() 
 {
// Can't spawn actors in constructor
 }

ABaseCharacter::BeginPlay()
{
    Super::BeginPlay();

    // Spawn melee system
    MeleeCombatSystem = GetWorld()->SpawnActor<AMeleeCombatSystem>(AMeleeCombatSystem::StaticClass);
}

Now after this, you should have a proper instance of AMeleeCombatSystem which would have access to all the Actor goodies.

Also, AMeleeCombatSystem::SomeFunction() would imply that you’re calling a static method on that class, which I don’t think is the case here.

2

Hi,

I have a setup where I have a ABaseCharacter which has several abilities, like talking to NPC, target enemies and so on. Yesterday I decided to make my MeleeCombatSystem more modular to reuse it in other projects.

Basically I did something like that:

ABaseCharacter::ABaseCharacter() 
{

}

void ABaseCharacter::startMelee() 
{
     // do stuff do stuff do stuff
    doSomethingWithTimerInMeleeCombat();
}

void ABaseCharacter::doSomethingWithTimerInMeleeCombat() 
{
    GetWorldTimerManager()-> // and so on
}

This works well, no issues. When I decided to make it more “modular” I changed my code to following

ABaseCharacter.h

// forward declaration 
class AMeleeCombatSystem;

class AMeleeCombatSystem : ABaseCharacter
{
AMeleeCombatSystem* meleeSystem;
}

ABaseCharacter.cpp

#include “Combat/MeleeCombatSystem.h”

ABaseCharacter::ABaseCharacter() 
{
   AMeleeCombatSystem *meleeSystem  = Cast<AMeleeCombatSystem>(AMeleeCombatSystem::StaticClass()->GetDefaultObject();
}

void ABaseCharacter::startMelee() 
{
    if(meleeSystem) 
    {
        meleeSystem->doSomethingWithTimerInMeleeCombat();
    }
}

/*** Inherit from baseCharacter in header file ***/
AMeleeCombatSystem : ABaseCharacter

In AMeleeCombatSystem.cpp

void AMeleeCombatSystem::doSomethingWithTimerInMeleeCombat()
{
      // do stuff do stuff do stuff
      GetWorldTimerManager()-> // CRASHED
}

I believe the issue is that this MeleeCombatSystem is not really in the UWorld* and just invoked by using AMeleeCombatSystem *meleeSystem = Cast(AMeleeCombatSystem::StaticClass()->GetDefaultObject();

So I tried to change it to the following

void AMeleeCombatSystem::doSomethingWithTimerInMeleeCombat()
{
      // do stuff do stuff do stuff
      ABaseCharacter::GetWorldTimerManager()-> // CRASHED also
}

Did someone ran into similar problems or am I looking in the wrong direction?
I am looking for a way to use GetWorldTimerManager() for this class which is not placed in the UWorld.

Thanks in advance

3

Thanks for you answer.
For some other modules I did it the same way like handling npc interaction and so on. I can access the class AMeleeCombatSystem and call every methods, which does not include GetWorldTimerManager();

I forgot to mention that AMeleeCombatSystem is derived from ABaseCharacter and that meleeCombatSystem is declared in my header file,I will update this.
I will try the UPROPERTY() in my header file definitly, but why does this help that GetWorldTimerManager() does not crash my engine?
I just try to understand :slight_smile:

4

I have the baseCharacter placed in the world, but not the MeleeTargetSystem.
So basically why should I prevent this actor from beeing garbage collected when it isn’t in the UWorld? Would this help in this case?

That why I tried ABaseCharacter::GetWorldTimerManager() because the base character is in the UWorld

I also tried GetWorld()->GetWorldTimerManager(); without success :confused:

I’m not on my UE pc but will give it a try later on :slight_smile:

5

Yes, UPROPERTY() prevents the Garbage Collector from destroying Actors. You will definitely run into problems if you don’t decorate your actor pointer declarations with it.

I think you could also try the following instead:

GetWorld()->GetWorldTimerManager()
6

No I don’t think so - Garbage Collection only applies to instances as far as I know.

Have you tried my suggestion of actually Spawning and instance of AMeleeCombatSystem?

edit:
Also see this post

I’m not sure exactly what GetDefaultObject() does but I suspect the problem comes from not calling GetWorldTimerManager() on a “proper” Actor instance.

7

Yes you are right something seems to be wrong with my instance, but beside that function which has a direct connection to UWorld everything else works.

Unfortunately I cannot try until I’m at home :slight_smile:
But if possible I want to avoid spawning an instance of MeleeTargetSystem because from mind point of view it should not be necessary in my implementation to spawn some kind of helper module
I will let you know the results if I was able to test this.
Thanks so far for your time and ideas:)

8

Hi Staticvoidlol,

I solved this by using one of your hints.
I did not derived this CombatSystem from my base character, since its better to have this independent. So I derived it from an actor directly and placed it into the UWorld.
Now I dont have any issue with the timer manager and a more loosely coupled module