如何把Vux的alert组件挂载到全局上

Question

项目中main.js中调用了,import { AlertPlugin } from 'vux'Vue.use(AlertPlugin);Vue.prototype.$msgbox = (title,msg) => {this.$vux.alert.show({    title: title,    content: msg});}这样子调用会报错Error in mounted hook: "TypeError: Cannot read property 'alert' of undefined"。求问要如何才可以把alert组件像这样子挂载到全局函数上去？