Template Refs Become Null When Elements Are Unmounted
Impact: MEDIUM - When using template refs with v-if, the ref becomes null when the element is unmounted. Watchers and effects that access these refs must handle the null case to avoid runtime errors.
This is especially tricky with watchEffect since it runs automatically and may execute when the ref is null.
Task Checklist
- Always check for null before accessing ref properties when using v-if
- In watchers, explicitly handle the null case (element unmounted or not yet mounted)
- Consider whether v-show is more appropriate if you need persistent ref access
- Use optional chaining (?.) when accessing ref properties in uncertain contexts
Incorrect:
<script setup>
import { ref, watchEffect } from 'vue'
const inputEl = ref(null)
const showInput = ref(true)
// WRONG: No null check - will error when v-if is false
watchEffect(() => {
inputEl.value.focus() // TypeError when showInput is false
})
</script>
<template>
<input v-if="showInput" ref="inputEl" />
<button @click="showInput = !showInput">Toggle</button>
</template>Correct:
<script setup>
import { ref, watchEffect } from 'vue'
const inputEl = ref(null)
const showInput = ref(true)
// CORRECT: Handle both mounted and unmounted states
watchEffect(() => {
if (inputEl.value) {
inputEl.value.focus()
} else {
// Element not mounted yet, or unmounted by v-if
console.log('Input element not available')
}
})
</script>
<template>
<input v-if="showInput" ref="inputEl" />
<button @click="showInput = !showInput">Toggle</button>
</template><script setup>
import { ref, watch } from 'vue'
const inputEl = ref(null)
const showInput = ref(true)
// CORRECT: Watch the ref and handle null explicitly
watch(inputEl, (el) => {
if (el) {
el.focus()
}
})
</script>
<template>
<input v-if="showInput" ref="inputEl" />
</template><script setup>
import { useTemplateRef, watchEffect } from 'vue'
// Vue 3.5+ approach
const input = useTemplateRef('my-input')
// CORRECT: Use optional chaining for safe access
watchEffect(() => {
input.value?.focus()
})
</script>
<template>
<input v-if="showInput" ref="my-input" />
</template><script setup>
import { ref, onMounted } from 'vue'
const inputEl = ref(null)
const showInput = ref(true)
// ALTERNATIVE: Use v-show if you need consistent ref access
// v-show keeps element in DOM, just hides it with CSS
</script>
<template>
<!-- Element always exists in DOM, ref is never null -->
<input v-show="showInput" ref="inputEl" />
</template>