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C++17 in Detail: A Deep Dive

Examples Of std::optional

Explore practical examples of using std optional in C++17 to manage nullable values and enhance code safety. Understand how optional fields like nicknames and ages can be implemented, how to parse command-line integers with error avoidance, and other common uses such as optional configurations and geometric computations. This lesson helps you grasp real-world applications of std optional to write cleaner and more robust C++ code.

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Here are a few more extended examples where std::optional fits nicely.

User Name with an Optional Nickname and Age

C++ 17
#include <optional>
#include <iostream>
using namespace std;
class UserRecord {
  public:
  UserRecord (string name, optional<string> nick, optional<int> age) : mName{move(name)}, mNick{move(nick)}, mAge{age}
  {
  }
  friend ostream& operator << (ostream& stream, const UserRecord& user);
  private:
  string mName;
  optional<string> mNick;
  optional<int> mAge; 
};
ostream& operator << (ostream& os, const UserRecord& user) {
  os << user.mName; if (user.mNick)
    os << ' ' << *user.mNick; if (user.mAge)
      os << ' ' << "age of " << *user.mAge; return os;
}
int main() {
  UserRecord tim { "Tim", "SuperTim", 16 };
  UserRecord nano { "Nathan", nullopt, nullopt };
  cout << tim << '\n';
  cout << nano << '\n';
}

The above example shows a simple class with optional fields. While the name is obligatory, the other attributes: “nickname” and “age” are optional.

Parsing ints From The

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