Thread: Attempting to learn OO design with C++

Hello, I am attempting to make a Duck interface which can produce different types of ducks. I was hoping you could look over my code, and point out possible issues, or suggest alternatives to better design. Sorry, but I don't have any specific question. This is the 1st c++ program I've made in a while and I'm trying to figure smart pointers out.

Here is my main Function

Code:

#include <iostream>#include "Duck.h"
#include <memory>
using std::cout;
std::unique_ptr < Duck > createDuck();
void operateDuck(Duck &);

int main()
{
  auto duck = createDuck();
  operateDuck(*duck);
  //duck = createDuck();
  //operateDuck(duck.get());
  return 0;
}

std::unique_ptr < Duck > createDuck()
{
  int op;
  cout << "1 for mallard, 2 for model.." << endl;
  cin >> op;
  switch (op) {
  case 1:
    cout << "Creating Mallard..." << endl;
    return std::make_unique < MallardDuck > ();
    break;
  case 2:
    cout << "Creating Model..." << endl;
    return std::make_unique < ModelDuck > ();
    break;
  default:
    cout << "Continuing.." << endl;
  }
}

void operateDuck(Duck & duck)
{
  int menuChoice;
  cout <<
      "Enter 1 to fly, 2 to flynomore, 3 to flyhigh, and 4 to quit, 5 to make new duck"
      << endl;
  cin >> menuChoice;
  while (menuChoice < 4) {
    cout << "Enter your choice again: " << endl;
    cin >> menuChoice;
    switch (menuChoice) {
    case 1:
      duck.performFly();
      break;
    case 2:
      duck.setFlyBehaviour(std::make_unique < FlyNoWay > ());
      break;
    case 3:
      duck.setFlyBehaviour(std::make_unique < FlyWithWings > ());
      break;
    case 4:
      cout << "Relinquishing command... " << endl;
      break;
    case 5:
      //recursively create new ducks until system failure
      break;
    default:
      cout << "No input..." << endl;
    }
  }
  cout << "Leaving OperateDuck() " << endl;

}

And here is my Duck.h

Code:

//// Created by playerone on 2019-10-24.
//

#ifndef OODESIGNEXAMPLES_DUCK_H
#define OODESIGNEXAMPLES_DUCK_H
#include "QuackBehaviour.h"
#include "FlyBehaviour.h"
#include <iostream>
#include <memory>

/*
 * class C {
 C(const C&) = default;               // Copy constructor
 C(C&&) = default;                    // Move constructor
 C& operator=(const C&) = default;  // Copy assignment operator
 C& operator=(C&&) = default;       // Move assignment operator
 virtual ~C() { }                     // Destructor
 };
 *
 */

class Duck {
public:
  Duck() = default;
  Duck(const Duck & other) = delete;  // we don't want to copy other duck's unique_ptr's
   Duck & operator=(const Duck &) = delete; //ducks are bred, not cloned
   Duck & operator=(Duck &&) = default;
   Duck(Duck && other) noexcept = default;
   virtual ~ Duck() = default;  //{std::cout << "Duck is being destroyed.." << endl;};
  virtual void display() = 0;
  void performFly() {
    flyBehaviour->fly();
  } void performQuack() {
    quackBehaviour->quack();
  }
  void swim() const {
    std::cout << "All ducks float, and are lighter than wood!" << endl;
  } void setFlyBehaviour(std::unique_ptr < FlyBehaviour > fb) {
    flyBehaviour = std::move(fb);
  }
  void setQuackBehaviour(std::unique_ptr < QuackBehaviour > qb) {
    quackBehaviour = std::move(qb);
  }
private:
  std::unique_ptr < FlyBehaviour > flyBehaviour = nullptr;
  std::unique_ptr < QuackBehaviour > quackBehaviour = nullptr;
};

class MallardDuck:public Duck {
public:
  MallardDuck() {
    //flyBehaviour = std::unique_ptr<FlyWithWings>(); //causes seg fault when flyBehaviour is protected (cant use assignment operator with unique_ptr??
    setFlyBehaviour(std::make_unique < FlyWithWings > ());
    setQuackBehaviour(std::make_unique < Quack > ());
  };
  //    ~MallardDuck() override { std::cout << "This mallard is being destroyed" << endl; }
  void display() override {
    std::cout << "Look at me I'm a mallard" << endl;
  }
};

class ModelDuck:public Duck {
public:
  ModelDuck() {
    setFlyBehaviour(std::make_unique < FlyNoWay > ());
    setQuackBehaviour(std::make_unique < Squeak > ());
  };
  //    ~ModelDuck() override { std::cout << "This model is being destroyed" << endl; }
  void display() override {
    std::cout << "This model duck looks beautiful today!" << endl;
  }
};

#endif                          //OODESIGNEXAMPLES_DUCK_H

The behaviour classes were trivial.
There are some weird things I don't understand, like when I use

Code:

delete

on the move constructor and assignment operator, the program still works? Other than that, I need to have good principles for an upcoming project in my software engineering course. This is what I was aiming for:

https://i.imgur.com/tNp74ay.png

Here is FlyBehaviour class, QuackBehaviour is the same:

Code:

#ifndef OODESIGNEXAMPLES_FLYBEHAVIOUR_H
#define OODESIGNEXAMPLES_FLYBEHAVIOUR_H

#include <iostream>
using namespace std;

class FlyBehaviour {
public:
  FlyBehaviour() = default;
  virtual ~ FlyBehaviour() {
    std::cout << "FlyBehaviour object is being destroyed.." << endl;
  };
  //FlyBehaviour(const FlyBehaviour&) = default;
  //FlyBehaviour&operator=(const FlyBehaviour&) = default;
  virtual void fly() = 0;
};

class FlyWithWings:public FlyBehaviour {
public:
  void fly() override {
    cout << "I'm a flying duck" << endl;
}};

class FlyNoWay:public FlyBehaviour {
public:
  void fly() override {
    cout << "I can't fly" << endl;
  };
};

#endif                          //OODESIGNEXAMPLES_FLYBEHAVIOUR_H

This DuckFactory is what I'm trying to implement.

Code:

//
// Created by playerone on 2019-10-31.
//

#ifndef DUCKINTERFACE_DUCKFACTORY_H
#define DUCKINTERFACE_DUCKFACTORY_H
#include <iostream>
#include <string>
#include <map>
#include <memory>
#include "Duck.h"
// Macro for class registration
#define REGISTER_FACTORY(derivedClass) \
   namespace { auto registry_ ## derivedClass = ConcreteFactory<derivedClass>(#derivedClass);  }

class DuckFactory {
private:
  using FactoryMap = std::map < std::string, DuckFactory * >;
  static auto getRegister()->FactoryMap & {
    static FactoryMap classRegister {
    };
     return classRegister;
} public:
    /** Register factory object of derived class **/
  static auto registerFactory(const std::string & name, DuckFactory * factory)->void {
    auto & reg = DuckFactory::getRegister();
    reg[name] = factory;
  } static auto showClasses()->void {
    std::cout << "Registered Classes:  " << endl;
    std::cout << "=====================" << endl;
    for (const auto & pair:DuckFactory::getRegister())
      std::cout << " + " << pair.first << endl;
  }
    /** Construct derived class returning raw ptr**/
      static auto makeRaw(const std::string & name)->Duck * {
    auto it = DuckFactory::getRegister().find(name);
    if (it != DuckFactory::getRegister().end())
      return it->second->construct();
    return nullptr;
  }

    /** Construct derived class returning unique ptr**/
  static auto makeUnique(const std::string & name)->std::unique_ptr < Duck > {
    return std::unique_ptr < Duck > (DuckFactory::makeRaw(name));
  }

  virtual ~ DuckFactory() = default;
  virtual auto construct() const->Duck * = 0;

};

template < typename DerivedClass > class ConcreteFactory:DuckFactory {
public:
  //Register this global object on the factory register
  explicit ConcreteFactory(const std::string & name) {
    std::cerr << " [TRACE] " << "Registered Class = " << name << endl;
    DuckFactory::registerFactory(name, this);
  }
  auto construct() const->Duck * override {
    return new DerivedClass;
}};

#endif                          //DUCKINTERFACE_DUCKFACTORY_H

and my main.cpp now looks like:

Code:

std::unique_ptr < Duck > createDuck();
void operateDuck(Duck &);
REGISTER_FACTORY(MallardDuck);
REGISTER_FACTORY(ModelDuck);

int main()
{
  DuckFactory::showClasses();
  cout << endl;
  std::unique_ptr < Duck > objMallard1 = DuckFactory::makeUnique("MallardDuck");
  cout << " type of objMallard1 = " << objMallard1->getType() << endl;

  std::unique_ptr < Duck > objModel1 = DuckFactory::makeUnique("ModelDuck");
  cout << " type of obModel1 = " << objModel1->getType() << endl;

  operateDuck(*objModel1);

}

Is this an acceptable way of doing a factory design?

Well I would first suggest you learn either to "copy as text" in your IDE or "paste as text" in your browser before posting more code - thanks.