TiedTupleOutput.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Templates/Tuple.h"
 
namespace Algo
{
    namespace Private
    {
        template <typename... OutputTypes>
        struct TTiedTupleAdder
        {
            template <typename TupleType>
            void Add(TupleType&& Values)
            {
                static_assert(TIsTuple<TupleType>::Value);
                static_assert(sizeof...(OutputTypes) == TTupleArity<typename TDecay<TupleType>::Type>::Value, "Wrong length of tuple for output");
 
                VisitTupleElements(
                    [](auto& Output, auto&& Value)
                    {
                        Output.Add(Forward<decltype(Value)>(Value));
                    },
                    Outputs,
                    Forward<TupleType>(Values)
                );
            }
 
            TTuple<OutputTypes&...> Outputs;
        };
    }
 
 
    /**
     * Ties n objects with an Add function, usually containers, into one object with an Add function accepting an n-tuple
     * that forwards the Add calls.
     *
     * This is useful for algorithms such as Algo::Transform and Algo::Copy.
     *
     * Example:
     *  TArray<int32> Out1;
     *  TArray<FString> Out2;
     *  TieTupleAdd(Out1, Out2).Add(MakeTuple(42, TEXT("42")));
     *  // Out1 = { 42 }, Out2 = { "42" }
     *
     *  @param Outputs Objects with an Add() function
     *  @return An object with an Add function that will call Add on the tied elements
     */
    template <typename... OutputTypes>
    Private::TTiedTupleAdder<OutputTypes...> TieTupleAdd(OutputTypes&... Outputs)
    {
        return { { Outputs... } };
    }
}