59: You Don't Need Constructors

This exercise is pending. Quick notes about this exercise:

• Talk about why C++ has the odd syntax to pre-initialize variables
• Show how you can use default initialization and designated initializers to avoid constructors.
• Talk about why you want to do this.
• Demonstrate that it's a performance gain most of the time, and show when it's not.

The Code

View Source file ex59.cpp Only

#include <fmt/core.h>
#include <chrono>
#include <thread>
#include <string>

struct SimplePerson {
  std::string name;
  int age{1};
  int pets{_guess_pets(age)};
  bool alive{true};

  std::string how_alive() {
    return alive ? "very alive" : "very dead";
  }

  void print() {
    fmt::println("I am {} and I am {} years old. I have {} pets and I am {}.",
        name, age, pets, how_alive());
  }

private:
  int _guess_pets(int age) {
    return age / 10 + 1;
  }
};

int main(int argc, char* argv[]) {
  // try doing the initialize like before to see the error
  SimplePerson baby{.name="Baby", .pets=0};
  baby.print();

  SimplePerson zed{.name="Zed", .age=51};
  zed.print();

  SimplePerson mary{.name="Mary", .age=28, .pets=1};
  mary.print();

  SimplePerson zombie{.name="Zombie", .age=100, .alive=false};
  zombie.print();
}

The Breakdown

line of code

Description.

The Discussion

Blah blah.

Further Study

• Do this next.