Vue 3: How to get and modify set variables in component functions

Question

Consider the following simple example using the composition API in Vue 3. I want to use an instance of test in a component's function.

<script>
import { defineComponent, ref, onMounted } from 'vue'

export default defineComponent({
  name: 'Test',
  setup(){
    let test = ref()
    
    onMounted(() => {
      doSomething()
    })

    return{
      test,
      doSomething
    }
  }
})

function doSomething(){
  console.log(test) //<-- undefined
  console.log(this.test) //<-- undefined
}
</script>

How to access test inside doSomething()? My understanding is that anything returned by setup() should be available throughout the component, just like the data() attribute in the options API.

Answer 1

You must pass ref as a parameter

<script>
import { defineComponent, ref, onMounted } from 'vue'

export default defineComponent({
  name: 'Test',
  setup () {
    let test = ref(null)

    onMounted(() => {
      doSomething(test.value)
    })

    return {
      test,
      doSomething
    }
  }
})

function doSomething (param) {
  console.log(param); // null
}
</script>

---

Another method:

// functions.js
import { ref } from 'vue'
export let test = ref(null)

// vue-file
<script>
import { defineComponent, ref, onMounted } from 'vue'
import { test } from '../utils/functions.js'

export default defineComponent({
  name: 'Test',
  setup () {

    onMounted(() => {
      doSomething(test)
    })

    return {
      test,
      doSomething
    }
  }
})

function doSomething (param) {
  console.log(test.value); // <-- instant access
  console.log(param.value); // <-- import via parameter
}
</script>