[构造函数](Classes/%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0.md) [extends](Classes/extends.md) [static](Classes/static.md) [项目实践](Classes/%E9%A1%B9%E7%9B%AE%E5%AE%9E%E8%B7%B5.md)