vue-class-component 安装
npm install vue-class-component vue-property-decorator --save-dev
get=>computed
set=>当检测到值发生变化是会调用set
参考：https://my.oschina.net/lpcysz/blog/2980469,https://blog.csdn.net/zhumizhumi/article/details/90479642,https://blog.csdn.net/sigmarising/article/details/90762737