觀察者模式
一個 Event Manager，提供兩個操作：
- 訂閱
- 通知
cpp
#include <thread>
#include <iostream>
#include <functional>
#include <unordered_map>
class EventManager {
public:
using CBFunc = std::function<void(const std::string&)>;
EventManager() {
}
void subscribe(const std::string& name,
const std::string &channelName, CBFunc cb) {
cbFuncs_[channelName][name] = cb;
}
void unsubscribe(const std::string& name, const std::string &channelName) {
auto it = cbFuncs_.find(channelName);
if (it == cbFuncs_.end()) {
return;
}
it->second.erase(name);
}
void notify(const std::string& channelName, const std::string& msg) {
auto it = cbFuncs_.find(channelName);
if (it == cbFuncs_.end()) {
return;
}
for (const auto& [subscriberName, cb]: it->second) {
cb(msg);
}
}
private:
std::unordered_map<std::string, std::unordered_map<std::string, CBFunc>>
cbFuncs_;
};