factory creating different types according to enum values c++

Question

I have some auto generated structs each logically related to a enum value. can I create a factory using a template function? everything can be resolved at compiled time. I tried something like this:

struct Type1
{
};    

struct Type2
{
};

enum class type_t
{
    first,
    second
};

template 
auto Get_()
{    
    static_assert(typet == type_t::second);
    return Type2();
}  

template 
auto Get_()
{
    static_assert(typet == type_t::first);
    return Type1();
} 
   
template 
auto Get_()
{
    static_assert(false, "no overload");
}    

int main()
{
    auto relatedType1 = Get_();
    auto relatedType2 = Get_();
}

user_18647949 · Answer

In C++11 (and above), you may use an auxiliary traits struct like the following:

template 
struct type_selector;

template <>
struct type_selector {
    using type = Type1;
};

template <>
struct type_selector {
    using type = Type2;
};

// implement other specializations, if needed

Then, your Get_ function template is simply:

template 
auto Get_() -> typename type_selector::type {
    return {};
}

factory creating different types according to enum values c++

1 Answers