Skip to content

Vue 3 Composition API: using props as initial value for component data

So I am building a search page in Vue 3 using the composition API. I have a component which takes a set of data from the parent and shows a snippet of the data including where the keyword is, and so it needs to make a working copy of this data to make a displayable value.

I had a lot of weird errors because I was initially using the following code, thinking it would just get the value:

setup(props) {

          const displayEntry = ref(props.entry)

...

but this ended up being reactive and changing the original data. I don’t need the reactivity because I create the component dynamically from the parent. I also don’t want to keep a working copy of the data in the parent because that will increase code complexity. I then tried a myriad of different solutions to try to break the reactivity until I got to simply:

displayEntry.value = props.entry

At which point my linter goes bananas…

error    Getting a value from the `props` in root scope of `setup()` will cause the value to lose reactivity  vue/no-setup-props-destructure

So what is the correct way to just get the value from a prop?

Answer

Turns out that I was somehow passing a reference in the parent. Following is my code:

setup(props) {
  watchEffect(() => {
      if (searchTerm.value == "") {
        filteredEntries.value = []
      } else {
        filteredEntries.value = entries.value.filter(searchFilter)
      }
    })

  return {
      searchTerm, filteredEntries, echo, showPreview
    }
}

And in the template:

<SearchPreview
    v-for="( entry, index ) in filteredEntries"
    :key="index"
    :entry="entry"
    :search-term="searchTerm"
  />

No clue why it passes a ref and I’m not sure how to just pass the value, but I fixed it in the component with the following hack:

const displayEntry = ref(JSON.parse(JSON.stringify(props.entry)))

(this leaves some nested properties undefined but I pass those separately to make it work)