Can I use a union mapping a list of member against a struct?

Question

I'd like to access member of a union by member name or by a "wrapped" structs, such as:

#include <iostream>

struct MyClass
{   
    union {
        int t1;
        float t2;
        struct {
            int t1;
            float t2; 
        } mySharedData;
    };

    MyClass() {
    }
};

int main()
{
    MyClass myClass;

    myClass.t2 = 10.1;
    std::cout << myClass.mySharedData.t2 << std::endl;
}

but it seems that t2 and mySharedData.t2 are not pointing to the same memory. Is there a way to do somethings like this? So I can access to a sub-group of members by its name or by grouped struct.

Answer 1

It seems you just want "alias" for your members.

union is NOT the solution.

You might, with a little different syntax, have those alias.

With

struct MyClass
{
    struct {
        int t1 = 0;
        float t2 = 0; 
    } mySharedData;

    MyClass() {}

    // const version omitted for simplicity.
#if VERSION_1
    auto operator ->() { return &mySharedData; }
#else
    auto& t1() { return mySharedData.t1; }
    auto& t2() { return mySharedData.t2; }
#endif
};

You might have

myClass->t1 = 42;     // version 1 o->t1 instead of o.t1
myClass.t2() = 10.1f; // version 2 o.t2() instead of o.t2()

std::cout << myClass.mySharedData.t2; // and regular access.

Demo