DefaultManagerInstanceTracker.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/Map.h"
#include "Engine/World.h"
    
 
AIMODULE_API DECLARE_LOG_CATEGORY_EXTERN(LogManagerInstanceTracker, Warning, All);
 
template<typename FManager>
struct TDefaultManagerInstanceTracker
{
    TMap<UWorld*, FManager*> WorldToInstanceMap;
    bool bCreateIfMissing = false;
 
    UE_DEPRECATED(5.1, "TDefaultManagerInstanceTracker is deprecated and will be removed. Consider inheriting from a subsystem instead.")
    TDefaultManagerInstanceTracker()
    {
    }
 
    UE_DEPRECATED(5.1, "TDefaultManagerInstanceTracker is deprecated and will be removed. Consider inheriting from a subsystem instead.")
    FManager* GetManagerInstance(UWorld& World)
    {
        FManager** FoundInstance = WorldToInstanceMap.Find(&World);
        if (FoundInstance)
        {
            return *FoundInstance;
        }
        else if (World.bIsTearingDown)
        {
            return nullptr;
        }
 
        FManager* NewInstance = nullptr;
        if (bCreateIfMissing)
        {
            NewInstance = NewObject<FManager>(&World);
            NewInstance->AddToRoot();
            WorldToInstanceMap.Add(&World, NewInstance);
            if (!FWorldDelegates::OnPostWorldCleanup.IsBoundToObject(this))
            {
                FWorldDelegates::OnPostWorldCleanup.AddRaw(this, &TDefaultManagerInstanceTracker::OnPostWorldCleanup);
            }
        }
        else
        {
            UE_LOG(LogManagerInstanceTracker, Warning
                , TEXT("Calling FManager::GetCurrent while no instance for world %s has been created, and bCreateIfMissing == false")
                , *World.GetName());
        }
 
        return NewInstance;
    }
 
    void OnPostWorldCleanup(UWorld* World, bool /*bSessionEnded*/, bool /*bCleanupResources*/)
    {
        FManager** FoundInstance = WorldToInstanceMap.Find(World);
        if (FoundInstance)
        {
            (*FoundInstance)->RemoveFromRoot();
            WorldToInstanceMap.Remove(World);
        }
    }
};