82 lines
3.0 KiB
Markdown
82 lines
3.0 KiB
Markdown
---
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title: Refs in Arrays and Collections Require .value
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impact: MEDIUM
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impactDescription: Refs inside reactive arrays, Maps, or Sets are NOT auto-unwrapped like in reactive objects
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type: capability
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tags: [vue3, reactivity, ref, arrays, collections, unwrapping]
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---
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# Refs in Arrays and Collections Require .value
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**Impact: MEDIUM** - Unlike when a ref is a property of a reactive object, refs inside reactive arrays, Maps, and Sets are NOT automatically unwrapped. You must access them with `.value`, and forgetting this leads to silent bugs.
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Vue only auto-unwraps refs when they are properties of reactive objects. When refs are elements in arrays or values in Maps/Sets, they remain as ref objects and require explicit `.value` access.
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## Task Checklist
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- [ ] Always use `.value` when accessing refs stored in reactive arrays
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- [ ] Always use `.value` when accessing refs stored in reactive Maps or Sets
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- [ ] Consider storing plain values instead of refs in collections to avoid confusion
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- [ ] Be aware of this when iterating over arrays containing refs
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**Incorrect:**
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```javascript
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import { ref, reactive } from 'vue'
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const books = reactive([ref('Vue 3 Guide')])
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const counts = reactive(new Map([['clicks', ref(0)]]))
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// WRONG: Refs in arrays are NOT unwrapped
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console.log(books[0]) // Ref object, not 'Vue 3 Guide'
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books[0] = 'New Title' // Replaces the ref, doesn't update it!
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// WRONG: Refs in Maps are NOT unwrapped
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console.log(counts.get('clicks')) // Ref object, not 0
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counts.get('clicks')++ // Does nothing useful
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```
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**Correct:**
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```javascript
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import { ref, reactive } from 'vue'
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const books = reactive([ref('Vue 3 Guide')])
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const counts = reactive(new Map([['clicks', ref(0)]]))
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// CORRECT: Use .value for refs in arrays
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console.log(books[0].value) // 'Vue 3 Guide'
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books[0].value = 'New Title' // Updates the ref's value
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// CORRECT: Use .value for refs in Maps
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console.log(counts.get('clicks').value) // 0
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counts.get('clicks').value++ // Increments to 1
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```
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```javascript
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// ALTERNATIVE: Just store plain values in collections (simpler)
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const books = reactive(['Vue 3 Guide', 'Vuex Handbook'])
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const counts = reactive(new Map([['clicks', 0]]))
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// No .value needed - but changes to individual items aren't independently reactive
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console.log(books[0]) // 'Vue 3 Guide'
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console.log(counts.get('clicks')) // 0
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// Mutations still trigger reactivity through the reactive wrapper
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books[0] = 'New Title' // Works
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counts.set('clicks', counts.get('clicks') + 1) // Works
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```
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```vue
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<template>
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<!-- In templates, refs in arrays also need special handling -->
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<div v-for="(book, index) in books" :key="index">
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<!-- If book is a ref, you'd need: -->
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{{ book.value }}
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<!-- Or use computed to unwrap them first -->
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</div>
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</template>
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```
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## Reference
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- [Vue.js Reactivity Fundamentals - Caveat in Arrays and Collections](https://vuejs.org/guide/essentials/reactivity-fundamentals.html#caveat-in-arrays-and-collections)
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