How to get the this instance in vue 3? - vue.js

Question

In vue 2+ I can easily get the instance of this as a result I can write something like this,
// main.js
app.use(ElMessage)
// home.vue
this.$message({
showClose: true,
message: 'Success Message',
type: 'success',
})
What should I do for vue 3 as,
Inside setup(), this won't be a reference to the current active
instance Since setup() is called before other component options are
resolved, this inside setup() will behave quite differently from this
in other options. This might cause confusions when using setup() along
other Options API. - vue 3 doc.

Answer 1

Using ElMessage directly
ElementPlus supports using ElMessage the same way as $message(), as seen in this example:
import { ElMessage } from 'element-plus'
export default {
setup() {
const open1 = () => {
ElMessage('this is a message.')
}
const open2 = () => {
ElMessage({
message: 'Congrats, this is a success message.',
type: 'success',
})
}
return {
open1,
open2,
}
}
}
Using $message()
Vue 3 provides getCurrentInstance() (an internal API) inside the setup() hook. That instance allows access to global properties (installed from plugins) via appContext.config.globalProperties:
import { getCurrentInstance } from "vue";
export default {
setup() {
const globals = getCurrentInstance().appContext.config.globalProperties;
return {
sayHi() {
globals.$message({ message: "hello world" });
},
};
},
};
demo
Note: Being an internal API, getCurrentInstance() could potentially be removed/renamed in a future release. Use with caution.

Answer 2

Providing a different method where the idea is to set a globally scoped variable to the _component property of the viewmodel/app or component:
pageVM = Vue.createApp({
data: function () {
return {
renderComponent: true,
envInfo: [],
dependencies: [],
userGroups: []
}
},
mounted: function () {
//Vue version 3 made it harder to access the viewmodel's properties.
pageVM_props = pageVM._component;
this.init();
},