NonNullPropertyUtils.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Misc/Optional.h"
 
namespace UE::CoreUObject
{
    enum class EAllowSetNullOnNonNullableBehavior : uint8
    {
        Disabled,
        Enabled
    };
    
#if WITH_EDITORONLY_DATA
    class FScopedSetNullOnNonNullable
    {
    public:
        // If set, InBehavior will adjust later code in stack to adopt the behavior
        // If not set, prevailing behavior is preserved
        COREUOBJECT_API explicit FScopedSetNullOnNonNullable(TOptional<EAllowSetNullOnNonNullableBehavior> InBehavior);
        COREUOBJECT_API ~FScopedSetNullOnNonNullable();
    
        EAllowSetNullOnNonNullableBehavior GetBehavior() const;     
    
    private:
        FScopedSetNullOnNonNullable(const FScopedSetNullOnNonNullable&) = delete;
        FScopedSetNullOnNonNullable(FScopedSetNullOnNonNullable&&) = delete;
        FScopedSetNullOnNonNullable& operator=(const FScopedSetNullOnNonNullable&) = delete;
        FScopedSetNullOnNonNullable& operator=(FScopedSetNullOnNonNullable&&) = delete;
        
        FScopedSetNullOnNonNullable* Previous;
        EAllowSetNullOnNonNullableBehavior Behavior;
        bool bIsBehaviorSet;
    };
 
    // Thread local, set with FScopedSetNullOnNonNullable
    // If true, will allow setting null on a NonNullable property
    // Some cases in editor deserialization requires null to be set on NonNull properties
    // Example: deserializing a previously null value to NonNullable property from the transaction buffer for Undo/Redo
    EAllowSetNullOnNonNullableBehavior AllowSetNullOnNonNullableBehavior();
#else
    inline EAllowSetNullOnNonNullableBehavior AllowSetNullOnNonNullableBehavior()
    {
        return  EAllowSetNullOnNonNullableBehavior::Disabled;
    }
#endif
}