前面已经介绍了Crow如何添加路由，添加插件，以及路由和插件的运行的机制，那么Crow本身是怎么运行起来的呢？

template<typename... Middlewares>
class Crow
{...template<typename... Middlewares>using App = Crow<Middlewares...>;using SimpleApp = Crow<>;
};

Crow类声明了两个别名，App用于带有插件的，SimpleApp用于不带插件的

template<typename... Middlewares>
class Crow
{...Crow(){}/// Construct Crow with a subset of middlewaretemplate<typename... Ts>Crow(Ts&&... ts):middlewares_(make_middleware_tuple(std::forward<Ts>(ts)...)){}...std::tuple<Middlewares...> middlewares_;
};

Crow的构造函数，使用模版参数初始化

参考