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105 lines
3.2 KiB
Markdown
105 lines
3.2 KiB
Markdown
---
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title: Template Ref Unwrapping Only Works for Top-Level Properties
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impact: MEDIUM
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impactDescription: Nested refs in template expressions render as [object Object] instead of their values
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type: capability
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tags: [vue3, reactivity, ref, template, unwrapping]
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---
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# Template Ref Unwrapping Only Works for Top-Level Properties
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**Impact: MEDIUM** - Vue only auto-unwraps refs that are top-level properties in the template render context. Nested refs (refs inside objects) are NOT unwrapped in expressions, causing `[object Object]` rendering or calculation errors.
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This caveat trips up developers when they store refs inside reactive objects or plain objects and try to use them in template expressions like `{{ object.count + 1 }}`.
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## Task Checklist
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- [ ] Keep refs at the top level of your setup return or script setup
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- [ ] Destructure nested refs to top-level variables before using in expressions
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- [ ] Be aware that text interpolation `{{ object.ref }}` DOES unwrap, but expressions `{{ object.ref + 1 }}` do NOT
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- [ ] Consider restructuring data to avoid nested refs in templates
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**Incorrect:**
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```vue
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<script setup>
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import { ref } from 'vue'
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const count = ref(0)
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const object = { id: ref(1) }
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</script>
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<template>
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<!-- WRONG: Nested ref in expression - does NOT unwrap -->
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<p>ID + 1 = {{ object.id + 1 }}</p>
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<!-- Renders: "ID + 1 = [object Object]1" -->
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<!-- Surprisingly, plain interpolation DOES work -->
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<p>ID = {{ object.id }}</p>
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<!-- Renders: "ID = 1" (unwrapped because it's the final expression) -->
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</template>
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```
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**Correct:**
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```vue
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<script setup>
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import { ref } from 'vue'
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const count = ref(0)
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const object = { id: ref(1) }
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// SOLUTION 1: Destructure to top-level
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const { id } = object
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</script>
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<template>
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<!-- CORRECT: Top-level ref unwraps in all expressions -->
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<p>Count + 1 = {{ count + 1 }}</p>
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<!-- Renders: "Count + 1 = 1" -->
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<!-- CORRECT: Destructured ref is now top-level -->
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<p>ID + 1 = {{ id + 1 }}</p>
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<!-- Renders: "ID + 1 = 2" -->
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</template>
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```
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```vue
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<script setup>
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import { ref, computed } from 'vue'
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const object = { id: ref(1) }
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// SOLUTION 2: Use computed for derived values
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const idPlusOne = computed(() => object.id.value + 1)
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</script>
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<template>
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<!-- CORRECT: Computed handles the .value access -->
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<p>ID + 1 = {{ idPlusOne }}</p>
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</template>
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```
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```vue
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<script setup>
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import { reactive } from 'vue'
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// SOLUTION 3: Use reactive object instead (refs inside reactive auto-unwrap)
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const object = reactive({ id: 1 })
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</script>
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<template>
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<!-- CORRECT: Plain reactive property works in expressions -->
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<p>ID + 1 = {{ object.id + 1 }}</p>
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</template>
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```
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```javascript
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// WHY this happens:
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// - Template compilation only adds .value to top-level identifiers
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// - {{ count + 1 }} compiles to: count.value + 1
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// - {{ object.id + 1 }} compiles to: object.id + 1 (no .value added!)
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// - Plain {{ object.id }} has special handling for display purposes
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```
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## Reference
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- [Vue.js Reactivity Fundamentals - Caveat when Unwrapping in Templates](https://vuejs.org/guide/essentials/reactivity-fundamentals.html#caveat-when-unwrapping-in-templates)
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