Implementing a compile-time “static-if” logic for different string types in a container

Question

I\'d like to write a function template that operates on a container of strings, for example a std::vector.

I\'d like to support both CString

Answer 1

One common way to solve this is to extract the required interface out into a trait class. Something like this:

template 
struct StringTraits
{
  static size_t size(const S &s) { return s.size(); }
  // More functions here
};


template 
void DoSomething(const ContainerOfStrings& strings)
{
    for (const auto & s : strings)
    {
      auto len = StringTraits::type>::size(s);
    }
}


// Anyone can add their own specialisation of the traits, such as:

template <>
struct StringTraits
{
  static size_t size(const CString &s) { return s.GetLength(); }
  // More functions here
};

Of course, you can then go fancy and change the function itself to allow trait selection in addition to the type-based selection:

template >
void DoSomething(const ContainerOfStrings& strings)