OverrideVoidReturnInvoker.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
// HEADER_UNIT_SKIP - Not included directly
 
#include "CoreTypes.h"
#include <type_traits>
 
template <typename ReturnType, typename FuncType>
struct TOverrideVoidReturnInvoker
{
    TOverrideVoidReturnInvoker(ReturnType InDefaultValue, FuncType InFunction)
        : DefaultValue(InDefaultValue)
        , Function(InFunction)
    {}
 
    template <typename... ArgTypes>
    bool operator()(ArgTypes&&... Args)
    {
        using FuncResultType = std::invoke_result_t<FuncType, ArgTypes...>;
        static_assert(std::disjunction_v<std::is_same<FuncResultType, void>, std::is_same<FuncResultType, ReturnType>>, "Passed in function should either return void or ReturnType");
 
        if constexpr (std::is_same_v<FuncResultType, void>)
        {
            Invoke(Function, Forward<ArgTypes>(Args)...);
            return DefaultValue;
        }
        else
        {
            return Invoke(Function, Forward<ArgTypes>(Args)...);
        }
    }
 
    ReturnType DefaultValue;
    FuncType Function;
};