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Master Software Design Patterns and Architecture in C++

Factory Method Examples

Explore the factory method design pattern in C++ by learning how to implement object creation using abstract classes and both simple and smart pointers. Understand cloning methods, unique_ptr ownership, and practical applications to improve your design skills.

We'll cover the following...

In this lesson, we’ll look at some examples of a simple factory method. We’ll make an interface (abstract class in the case of C++) named Window, and we will have two classes: DefaultWindow and Fancywindow, which will implement the Window. For object creation, we will have getNewWindow() as a concrete creator. Let’s take a look at its code.

We’ll create a factory method with simple pointers in this ...

C++
#include <iostream>
// Product
class Window{ 
  public: 
    virtual Window* clone() = 0; 
    virtual ~Window() {};
};
// Concrete Products 
class DefaultWindow: public Window { 
  public:
    DefaultWindow() {
      std::cout << "DefaultWindow" << '\n';
    }
  private:
    DefaultWindow* clone() { 
      std::cout << "DefaultWindow clone" << '\n';
      return new DefaultWindow();
    } 
};
class FancyWindow: public Window { 
  public:
    FancyWindow() {
	  std::cout << "FancyWindow" << '\n';
	}
  private:
    FancyWindow* clone() { 
      std::cout << "FancyWindow clone" << '\n';
      return new FancyWindow();
    } 
};
// Concrete Creator or Client
Window* getNewWindow(Window& oldWindow) { 
  return oldWindow.clone();
}
  
int main(){
  DefaultWindow defaultWindow;
  FancyWindow fancyWindow;
  
  const Window* defaultWindow1 = getNewWindow(defaultWindow);
  const Window* fancyWindow1 = getNewWindow(fancyWindow);
  
  delete defaultWindow1;
  delete fancyWindow1;
  
}

Note: We can’t create the Window class ...