design-patterns-cpp/builder/Builder.cpp

/*
 * C++ Design Patterns: Builder
 * Author: Jakub Vojvoda [github.com/JakubVojvoda]
 * 2016
 *
 * Source code is licensed under MIT License
 * (for more details see LICENSE)
 *
 */

#include <iostream>

/*
 * Product
 * the final object that will be created using Builder
 */
class Product {
public:
  void makeA(const std::string &part) {
    partA = part;
  }
  void makeB(const std::string &part) {
    partB = part;
  }
  void makeC(const std::string &part) {
    partC = part;
  }
  std::string get() {
    return (partA + " " + partB + " " + partC);
  }
  // ...
  
private:
  std::string partA;
  std::string partB;
  std::string partC;
  // ...
};

/*
 * Builder
 * abstract interface for creating products
 */
class Builder {
public:
  virtual ~Builder() {
    // ...
  }

  Product get() {
    return product;
  }

  virtual void buildPartA() = 0;
  virtual void buildPartB() = 0;
  virtual void buildPartC() = 0;
  // ...
  
protected:
  Product product;
};

/*
 * Concrete Builder X and Y
 * create real products and stores them in the composite structure
 */
class ConcreteBuilderX : public Builder {
public:
  void buildPartA() {
    product.makeA("A-X");
  }
  void buildPartB() {
    product.makeB("B-X");
  }
  void buildPartC() {
    product.makeC("C-X");
  }
  // ...
};

class ConcreteBuilderY : public Builder {
public:
  void buildPartA() {
    product.makeA("A-Y");
  }
  void buildPartB() {
    product.makeB("B-Y");
  }
  void buildPartC() {
    product.makeC("C-Y");
  }
  // ...
};

/*
 * Director
 * responsible for managing the correct sequence of object creation
 */
class Director {
public:
  Director() : builder(nullptr) {}

  ~Director() {
    if (builder) {
      delete builder;
    }
  }

  void set(Builder *b) {
    if (builder) {
      delete builder;
    }
    builder = b;
  }

  Product get() {
    return builder->get();
  }

  void construct() {
    builder->buildPartA();
    builder->buildPartB();
    builder->buildPartC();
    // ...
  }
  // ...

private:
  Builder *builder;
};


int main()
{
  Director director;
  director.set(new ConcreteBuilderX);
  director.construct();

  Product product1 = director.get();
  std::cout << "1st product parts: " << product1.get() << std::endl;

  director.set(new ConcreteBuilderY);
  director.construct();

  Product product2 = director.get();
  std::cout << "2nd product parts: " << product2.get() << std::endl;

  return 0;
}