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

If you cannot(/don't want to) change ConditionalData, you may create 2 methods instead:

template
void SetData(ConditionalData& , const T& ) {/* Nothing */}

template
void SetData(ConditionalData& c, const T& value) { c.setData(value); }

and then

A() {
    ConditionalData data;
    SetData(data, 3);
}

For more complex cases

template
void A_impl_part1(ConditionalData&) {/* Nothing */}

template
void A_impl_part1(ConditionalData& c) { c.setData(3); }

and then

A() {
    ConditionalData data;
    A_impl_part1(data);
    // common part
    // A_impl_part2(data); // and so on
}