CppPatterns/Builder/main.cpp

#include <iostream>
#include <memory>
#include <numeric>
#include <vector>

std::string join(const std::vector<std::string> &values,
                 const std::string &separator) {
  if (values.empty()) {
    return "";
  } else {
    return std::accumulate(
        std::next(values.begin()), values.end(), values.front(),
        [&separator](const std::string &left, const std::string &right) {
          return left + separator + right;
        }

    );
  }
}

class Product {
public:
  std::vector<std::string> parts;

  void listParts() const {
    std::cout << "Parts: " << join(parts, ", ") << std::endl;
  }
};

class Builder {
public:
  virtual ~Builder() = default;
  virtual const Builder &addPartA() const = 0;
  virtual const Builder &addPartB() const = 0;
  virtual const Builder &addPartC() const = 0;
};

class ConcreteBuilder : public Builder {
private:
  Product *product = nullptr;

public:
  ConcreteBuilder() { reset(); }
  ~ConcreteBuilder() { delete product; }

  void reset() {
    if (product != nullptr) {
      delete product;
    }
    product = new Product();
  }

  const Builder &addPartA() const override {
    product->parts.push_back("Part A");
    return *this;
  }
  const Builder &addPartB() const override {
    product->parts.push_back("Part B");
    return *this;
  }
  const Builder &addPartC() const override {
    product->parts.push_back("Part C");
    return *this;
  }

  Product *getProduct() {
    Product *result = product;
    product = nullptr;
    return result;
  }
};

class Director {
private:
  Builder *builder = nullptr;

public:
  Director(Builder *builder) : builder(builder) {}

  void buildSimpleProduct() { builder->addPartA(); }
  void buildFullProduct() { builder->addPartA().addPartB().addPartC(); }
};

int main(int argc, char *argv[]) {

  std::cout << "Builder" << std::endl;

  ConcreteBuilder builder = ConcreteBuilder();
  Director director(&builder);

  director.buildSimpleProduct();
  auto simple_product = std::unique_ptr<Product>(builder.getProduct());
  simple_product->listParts();

  builder.reset();
  director.buildFullProduct();
  auto full_product = std::unique_ptr<Product>(builder.getProduct());
  full_product->listParts();

  return EXIT_SUCCESS;
}