一个通过宏在工厂类中注册产品类的实现例子

#include <functional>
#include <iostream>
#include <memory>
#include <unordered_map>

class AbstractModule {
public:
  virtual void show() = 0;
};

class ConcreteModule1 : public AbstractModule {
public:
  void show() override {
    std::cout << "In ConcreteModule1 show()." << std::endl;
  }
  static std::shared_ptr<AbstractModule> create() {
    std::cout << "In ConcreteModule1 create()." << std::endl;
    return std::make_shared<ConcreteModule1>();
  }
};

class ConcreteModule2 : public AbstractModule {
public:
  void show() override {
    std::cout << "In ConcreteModule2 show()." << std::endl;
  }
  static std::shared_ptr<AbstractModule> create() {
    std::cout << "In ConcreteModule2 create()." << std::endl;
    return std::make_shared<ConcreteModule2>();
  }
};

static std::unordered_map<std::string,
                          std::function<std::shared_ptr<AbstractModule>()>>
    m;

class Factory {
public:
  static void
  registorModule(std::string modulename,
                 std::function<std::shared_ptr<AbstractModule>()> f) {
    m.insert(std::make_pair(modulename, f));
  }
  static std::shared_ptr<AbstractModule> getModule(std::string modulename) {
    if (m.count(modulename)) {
      return (m.at(modulename))();
    }
    return nullptr;
  }
};

#define REGISTOR(classname)                                                    \
  Factory::registorModule(#classname, classname::create);

int main(int argc, char *argv[]) {
  REGISTOR(ConcreteModule1);
  REGISTOR(ConcreteModule2);
  std::shared_ptr<AbstractModule> cm1 = Factory::getModule("ConcreteModule1");
  if (cm1) {
    cm1->show();
  }
  std::shared_ptr<AbstractModule> cm2 = Factory::getModule("ConcreteModule2");
  if (cm2) {
    cm2->show();
  }
  std::shared_ptr<AbstractModule> cm3 = Factory::getModule("ConcreteModule3");
  if (cm3) {
    cm3->show();
  }
  return 1;
}