Structured Member Value Access Using Structure Member Pointer and Variadic Templates, C++ (vc++)

Structured Member Value Access Using Structure Member Pointer and Variadic Templates

//Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x86

#include <iostream>
#include <typeinfo>
#include <string>
using namespace std;

struct TRC
{
    int data;
    std::string str;
};

struct XRC
{
    int v;
    TRC trc;
};

struct CRC
{
    int k;
    float g;
    XRC xrc;
};

struct EX_STRUCT
{
    int a;
    float b;
    char ch;
    CRC crc;
};

template<typename T, typename Visitable>
T& GetValueRef(Visitable& obj, T Visitable::* member)
{
    return obj.*member;
}

template <typename T>
T* GetValueAddress(T& obj)
{
    return &obj;
}

template<typename ObjectReference, typename MemberPointer, typename... Args>
void* GetValueAddress(ObjectReference& objRef, MemberPointer memberPtr, Args... args)
{
    return GetValueAddress(GetValueRef(objRef, memberPtr), args...);
};

template<typename T, typename... Args>
T GetValue(Args... args)
{
    void * valPtr = GetValueAddress(args...);
    return *reinterpret_cast<T*>(valPtr);
}

EX_STRUCT myStruct;

int main()
{
    myStruct.a = 200;
    myStruct.b = 3.14f;
    myStruct.crc.k = 450;
    myStruct.crc.xrc.v = 111;
    myStruct.crc.xrc.trc.data = 555;
    myStruct.crc.xrc.trc.str = "Hello World";
    
    std::cout << "EX_STRUCT::a value: " << GetValue<int>(myStruct, &EX_STRUCT::a) << endl;
    std::cout << "EX_STRUCT::b value: " << GetValue<float>(myStruct, &EX_STRUCT::b) << endl;
    std::cout << "EX_STRUCT::CRC::k value: " << GetValue<int>(myStruct, &EX_STRUCT::crc, &CRC::k) << endl;
    std::cout << "EX_STRUCT::CRC::XRC::v value: " << GetValue<int>(myStruct, &EX_STRUCT::crc, &CRC::xrc, &XRC::v) << endl;
    std::cout << "EX_STRUCT::CRC::XRC::TRC::data value: "<<GetValue<int>(myStruct, &EX_STRUCT::crc, &CRC::xrc, &XRC::trc, &TRC::data) << endl;
    std::cout << "EX_STRUCT::CRC::XRC::TRC::str value: " << GetValue<std::string>(myStruct, &EX_STRUCT::crc, &CRC::xrc, &XRC::trc, &TRC::str) << endl;
    return 0;
}


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