NonNullSubclassOf.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "UObject/Class.h"
#include "UObject/Field.h"
#include "SubclassOf.h"
#include "Misc/IntrusiveUnsetOptionalState.h"
 
// So we can construct uninitialized TNonNullSubclassOf
enum class EDefaultConstructNonNullSubclassOf { UnsafeDoNotUse };
 
template <typename T>
class TNonNullSubclassOf : public TSubclassOf<T>
{
    using Super = TSubclassOf<T>;
 
public:
    [[nodiscard]] UE_FORCEINLINE_HINT TNonNullSubclassOf(EDefaultConstructNonNullSubclassOf)
        : Super(nullptr)
    {
    }
 
    template <
        typename PtrType
        UE_REQUIRES(std::is_same_v<PtrType, UClass> || std::is_same_v<PtrType, FFieldClass>)>
    [[nodiscard]] inline TNonNullSubclassOf(PtrType* From)
        : Super(From)
    {
        checkf(From, TEXT("Initializing TNonNullSubclassOf with null"));
    }
 
    template <
        typename U
        UE_REQUIRES(std::is_convertible_v<U*, T*>)
    >
    [[nodiscard]] UE_FORCEINLINE_HINT TNonNullSubclassOf(const TSubclassOf<U>& From)
        : Super(From)
    {
    }
 
    template
    <
        typename U
        UE_REQUIRES(std::is_convertible_v<U*, T*>)
    >
    inline TNonNullSubclassOf& operator=(const TSubclassOf<U>& From)
    {
        checkf(*From, TEXT("Assigning null to TNonNullSubclassOf"));
        Super::operator=(From);
        return *this;
    }
    
    template <typename PtrType>
    inline TNonNullSubclassOf& operator=(PtrType* From)
    {
        checkf(From, TEXT("Assigning null to TNonNullSubclassOf"));
        Super::operator=(From);
        return *this;
    }
 
    // Start - intrusive TOptional<TNonNullSubclassOf> state //
    constexpr static bool bHasIntrusiveUnsetOptionalState = true;
    using IntrusiveUnsetOptionalStateType = TNonNullSubclassOf;
    [[nodiscard]] UE_FORCEINLINE_HINT explicit TNonNullSubclassOf(FIntrusiveUnsetOptionalState)
        : Super(nullptr)
    {
    }
    
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator==(FIntrusiveUnsetOptionalState) const
    {
        return Super::Get() == nullptr;
    }
    // End - intrusive TOptional<TNonNullSubclassOf> state //
};