Add factory example

cpp/patterns/factory/CMakeLists.txt

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+###############################################################################
+## Author: Shaun Reed                                                        ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved               ##
+## About: A project for practicing the factory C++ design pattern            ##
+##                                                                           ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0  ##
+##############################################################################
+#
+cmake_minimum_required(VERSION 3.15)
+project(
+    #[[NAME]]   Factory
+    VERSION     1.0
+    DESCRIPTION "An example of the factory design pattern in C++"
+    LANGUAGES   CXX
+)
+add_compile_options("-Wall")
+
+add_library(parts "parts.cpp")
+add_library(factory "factory.cpp")
+add_executable(factory-test "main.cpp")
+target_link_libraries(factory-test factory parts)

cpp/patterns/factory/factory.cpp

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+
+#include <iostream>
+
+#include "factory.hpp"
+
+Part* GearFactory::requestPart() {
+  // Create a new part
+  Part * newPart = makePart();
+  // Increment the QTY for part in AbstractFactory::inventory base class
+  // + If the item is not in the inventory map, this will also add it first.
+  inventory[newPart->getName()]++;
+  // Make the requested part
+  return newPart;
+}
+
+Part* GearFactory::requestPart(std::string partName, float price)
+{
+  Part * newPart = makePart(partName, price);
+  inventory[newPart->getName()]++;
+  return newPart;
+}
+
+void GearFactory::showStock() const
+{
+  for (const auto &item : inventory) {
+    if (item.first.empty()) continue; // Don't show an empty item
+    std::cout << item.first << " QTY in stock: " << item.second << std::endl;
+  }
+}
+
+
+/*****************************************************************************/
+// Gear
+
+Part* GearFactory::makePart() {
+  return new Gear();
+}
+
+Part* GearFactory::makePart(std::string name, float price)
+{
+  return new Gear(name, price);
+}

cpp/patterns/factory/factory.hpp

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+
+#ifndef FACTORY_HPP
+#define FACTORY_HPP
+
+#include <array>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "parts.hpp"
+
+// Gear Concrete Factory
+class GearFactory {
+public:
+  explicit GearFactory(std::string name_="GearFactory") :
+      name(std::move(name_)) {}
+
+  Part* requestPart();
+  Part* requestPart(std::string partName, float price);
+  void showStock() const;
+  std::string getName() const { return name;}
+
+protected:
+  Part* makePart();
+  Part* makePart(std::string name, float price);
+
+private:
+  std::string name;
+  std::unordered_map<std::string, int> inventory;
+};
+
+#endif // FACTORY_HPP

cpp/patterns/factory/main.cpp

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+
+#include <array>
+#include <cstdlib>
+#include <iostream>
+#include <vector>
+
+#include "factory.hpp"
+
+int main(const int argc, const char * argv[]) {
+  // Testing GearFactory
+  GearFactory gearFactory;
+  const int gearsRequired = 5;
+
+  std::cout << "Testing " << gearFactory.getName() <<"...\nMaking 5 Gears...\n";
+  for (int i = 0; i < gearsRequired; i++) gearFactory.requestPart();
+  std::cout << std::endl << gearFactory.getName() << " inventory:\n";
+  gearFactory.showStock();
+
+  // Making custom gears
+  for (int i = 0; i < gearsRequired; i++) gearFactory.requestPart("Big Gear", 2.5f);
+  std::cout << std::endl << gearFactory.getName() << " inventory:\n";
+  gearFactory.showStock();
+
+}

cpp/patterns/factory/parts.cpp

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+
+#include "parts.hpp"
+
+/*****************************************************************************/
+// Gear
+
+Gear::Gear(std::string name, float price) {
+  partName = name;
+  partPrice = price;
+}

cpp/patterns/factory/parts.hpp

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+
+#ifndef PARTS_HPP
+#define PARTS_HPP
+
+#include <string>
+
+class Part {
+public:
+  std::string getName() const { return partName;}
+  float getPrice() const { return partPrice;}
+
+protected:
+  std::string partName; // The name of the part
+  float partPrice; // The partPrice of the part
+};
+
+
+/*****************************************************************************/
+// Gear
+
+class Gear : public Part {
+public:
+  explicit Gear(std::string name="Gear", float price = 1.0f);
+};
+
+#endif // PARTS_HPP