Vue.js refs are undefined, even though this.$refs shows theyre there

Question

I have a reference to a component

<Gmap ref="mapRef">

In mounted I am doing this, to see the objects are available

mounted(){
    let self = this
    console.log(self.$refs) // Shows the mapRef object reference
    console.log(self.$refs.mapRef) // returns undefined ???
}

self.$refs shows...

  mapRef: VueComponent {_uid: 207, _isVue: true, $options: {…}, _renderProxy: Proxy, _self: VueComponent, …}

So then why does self.$refs.mapRef return undefined?? Even though it's clearly there??

Answer 1

I solved this by using v-show instead of v-if.

I had the component inside a v-if statement.

 <div v-if="!isLoading"> 
   <GMap ref="mapRef" />
 </div>

I just changed that to v-show

<div v-show="!isLoading"> 
   <GMap ref="mapRef" />
 </div>

And now the object is available in mounted(). Still find it strange that the console.log(this.$refs) showed it being available as a key on this.$refs, even though it actually wasn't? Thats strange behaviour.

The other wierd thing was, that even if I tried to access this.$refs.mapRef in my data loading section, AFTER THE DATA WAS LOADED, (ie after isLoading=false), I still couldn't access it. Even though then, it should've been available because the v-if passed.

So v-show solved it, by just hiding the div, instead of not rendereding it. Stupid little workaround.

Answer 2

I had a similar problem getting a ref to a leaflet map instance, try waiting for the "nextTick"

mounted(){
  this.$nextTick(()=>{
    let self = this
    console.log(self.$refs) // Shows the mapRef object reference
    console.log(self.$refs.mapRef) // returns undefined ???
  });
}

see the docs for more- https://v2.vuejs.org/v2/api/#vm-nextTick and https://v2.vuejs.org/v2/api/#mounted

Answer 3

Main solution is to make sure your component is not imported dynamically

You'd still need to also avoid wrapping your component with v-if and use this.$refs.mapRef in mounted() , instead of created()

I wasn't using Vue Google Maps plugin/component, but my own custom component

---

Method 1

Use:

import CustomComponent from './CustomComponent ';

export default {
  components: {
    CustomComponent,
  },
  ...
}

Instead of

export default {
  components: {
    CustomComponent: () => import('./CustomComponent'),
  },
  ...
}

---

Method 2

Use this.$refs.mapRef in mounted() instead of created() .

This way, setTimeout() and this.$nextTick() not needed

Correct way:

mounted(){
  //works! child components were loaded
  console.log(this.$refs.mapRef) 
}

Wrong way:

created(){
  //DON'T DO THIS! child components hasn't loaded
  console.log(this.$refs.mapRef) 

  //might work but it's an unreliable workaround
  setTimeout(()=>{
    console.log(this.$refs.mapRef)
  }, 0);

  //might work but it's an unreliable workaround
  this.$nextTick(()=>{
    console.log(this.$refs.mapRef)
  });

}

---

Method 3

Do not wrap child component using v-if , use v-show instead.

Correct way:

 <div v-show="!isLoading"> 
   <GMap ref="mapRef" />
 </div>

Wrong way:

 <div v-if="!isLoading"> 
   <GMap ref="mapRef" />
 </div>

---

Other Methods (not proper & not a solution)

The following are methods I tried but didn't work until I used the methods on top (stopped using dynamic import)

I already put this.$refs.mapRef in mounted() tried to wrap it with setTimeout() and 2 layers of this.$nextTick() .

It works only on hot reload, but no longer works after a page refresh

mounted(){
  setTimeout(()=>{
    this.$nextTick(()=>{
      this.$nextTick(()=>{
        console.log(this.$refs.mapRef) // returns undefined
      });
    });
  }, 0);
}

Thanks to this comment in another answer: How to access to a child method from the parent in vue.js

Answer 4

You can wrap your function in the $mapPromise method provided by vue2-google-maps , which will ensure that the Map has fully rendered before running your code:

let self = this;
self.$refs.mapRef.$mapPromise.then(() => {
    console.log(self.$refs.mapRef);
})

This should solve any problem where your code relies the Google Map to be fully rendered in order to run.

*NOTE: $mapPromise was named $mapCreated in past versions.

See Docs: https://github.com/Jeson-gk/vue2-google-maps/blob/master/API.md#mapcreated--promisegooglemapsmap

-

The reason why console.log(self.$refs); was showing the value when you looked, is that self.$refs is passed by reference. So, by the time you viewed the console, the rest of the data finished loading in a matter of milliseconds. And self.$ref.mapRef is not passed by reference, so it remains undefined , as it was during runtime.

Try adding a breakpoint directly after console.log(self.$refs); and before console.log(self.$refs.mapRef);and you will probably find that the data had not loaded.

Answer 5

就我而言，我将 ref 与 v-for 一起使用，我错过了仅在 v-for 在 dom 中呈现后才生成 ref 的事实，并且我将 v-for 与填充了几秒钟的状态数组属性一起使用在调用 mount 之后，我试图在填充状态数组之前访问我的 ref。

Answer 6

Seems like you're using: https://github.com/diegoazh/gmap-vue , as the docs says: https://diegoazh.github.io/gmap-vue/#lazy-loading

async mounted() {
    await this.$gmapApiPromiseLazy()

    ...
}

This works perfectly.

Answer 7

您可以按如下方式使用它，但我不知道它是否会破坏商业项目的打字稿实现。

(this as any).$refs.mapRef