C++ 观察者设计模式

观察者模式

观察者模式实现

#include <iostream>
#include <memory>
#include <string>
#include <vector>

class observer;
class subscriber : public std::enable_shared_from_this<subscriber> {
public:
  subscriber(const std::string& user_name) : user_name_(user_name) {
  }

  void callback(const std::string& str) {
    std::cout << user_name_ << ": " << str << std::endl;
  }
private:
  std::string user_name_;
};

class observer {
public:
  void boardcast(const std::string& message) {
    for (auto it = vec.begin(); it != vec.end();) {
      auto sp = it->lock();
      if (sp) {
        sp->callback(message);
        it++;
      } else {
        it = vec.erase(it);
      }
    }
  }

  void regist(std::weak_ptr<subscriber> wp) {
    if (wp.lock()) {
      vec.push_back(wp);
    }
  }
private:
  std::vector<std::weak_ptr<subscriber>> vec;
};

int main() {
  auto ob = std::make_shared<observer>();
  auto sp1 = std::make_shared<subscriber> ("subscriber1");
  ob->regist(sp1->weak_from_this());
  auto sp2 = std::make_shared<subscriber> ("subscriber2");
  ob->regist(sp2->weak_from_this());
  {
    auto sp3 = std::make_shared<subscriber> ("subscriber3");
    ob->regist(sp3->weak_from_this());
    auto sp4 = std::make_shared<subscriber> ("subscriber4");
    ob->regist(sp4->weak_from_this());
    ob->boardcast("start boardcast!");
  }
  ob->boardcast("boardcast again!");
  return 0;
}