CODESAMPLE

Template Method - C++

Template Method C++

The Template Method pattern defines the skeleton of an algorithm in an abstract class, but lets subclasses redefine certain steps of the algorithm without changing its structure. It’s a behavioral pattern used for code reuse and to avoid redundant code.

The C++ code below implements the Template Method pattern for building a house. The HouseBuilder abstract class defines the overall process of building a house (buildHouse()) as a template method. Concrete builders like WoodenHouseBuilder and ConcreteHouseBuilder override the specific steps (buildWalls(), buildRoof(), etc.) to create different types of houses, while the core sequence defined in buildHouse() remains consistent. This aligns with C++’s OOP principles, utilizing abstract classes and polymorphism.

#include <iostream>
#include <string>

// Abstract class
class HouseBuilder {
public:
  virtual ~HouseBuilder() {}

  void buildHouse() {
    buildWalls();
    buildRoof();
    installWindows();
    installDoors();
    paintHouse();
  }

protected:
  virtual void buildWalls() = 0;
  virtual void buildRoof() = 0;
  virtual void installWindows() = 0;
  virtual void installDoors() = 0;
  virtual void paintHouse() = 0;
};

// Concrete class 1
class WoodenHouseBuilder : public HouseBuilder {
protected:
  void buildWalls() override {
    std::cout << "Building wooden walls" << std::endl;
  }

  void buildRoof() override {
    std::cout << "Building a wooden roof" << std::endl;
  }

  void installWindows() override {
    std::cout << "Installing wooden windows" << std::endl;
  }

  void installDoors() override {
    std::cout << "Installing wooden doors" << std::endl;
  }

  void paintHouse() override {
    std::cout << "Painting the wooden house" << std::endl;
  }
};

// Concrete class 2
class ConcreteHouseBuilder : public HouseBuilder {
protected:
  void buildWalls() override {
    std::cout << "Building concrete walls" << std::endl;
  }

  void buildRoof() override {
    std::cout << "Building a concrete roof" << std::endl;
  }

  void installWindows() override {
    std::cout << "Installing concrete windows" << std::endl;
  }

  void installDoors() override {
    std::cout << "Installing concrete doors" << std::endl;
  }

  void paintHouse() override {
    std::cout << "Painting the concrete house" << std::endl;
  }
};

int main() {
  WoodenHouseBuilder woodenBuilder;
  ConcreteHouseBuilder concreteBuilder;

  woodenBuilder.buildHouse();
  std::cout << std::endl;
  concreteBuilder.buildHouse();

  return 0;
}