Cleanest way for conditional code instantiation in C++ template

Question

I\'m trying to get the following C++ code running:

#include 

template class ConditionalData {
};

template 

        

Answer 1

you can define setData for both branches, empty one for false condition:

template class ConditionalData {
};

template  class ConditionalData {
    void setData(T _data) {}
};

template  class ConditionalData {
private:
    T data;
public:
    void setData(T _data) { data = _data; }
};

template class A {
public:
    A() {
        ConditionalData data;
        data.setData(3);
    }
};