lib/optionalmember.cpp

The following code example is taken from the book
C++17 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2017
The code is licensed under a Creative Commons Attribution 4.0 International License.

---

// raw code

#include <string>
#include <optional>
#include <iostream>

class Name
{
  private:
    std::string first;
    std::optional<std::string> middle;
    std::string last;
  public:
    Name (std::string f,
          std::optional<std::string> m,
          std::string l)
     : first{std::move(f)}, middle{std::move(m)}, last{std::move(l)} {
    }
    friend std::ostream& operator << (std::ostream& strm, const Name& n) {
      strm << n.first << ' ';
      if (n.middle) {
        strm << *n.middle << ' ';
      }
      return strm << n.last;
    }
};

int main()
{
    Name n{"Jim", std::nullopt, "Knopf"};
    std::cout << n << '\n';

    Name m{"Donald", "Ervin", "Knuth"};
    std::cout << m << '\n';
}