184 lines
3.3 KiB
Markdown
184 lines
3.3 KiB
Markdown
---
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name: component-v-model
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description: Implement two-way data binding on custom components
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---
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# Component v-model
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Create two-way bindings between parent and child components.
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## defineModel() (3.4+, Recommended)
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The simplest way to implement v-model:
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```vue
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<!-- Child.vue -->
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<script setup lang="ts">
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const model = defineModel<string>()
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</script>
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<template>
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<input v-model="model" />
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</template>
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```
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```vue-html
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<!-- Parent.vue -->
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<Child v-model="searchText" />
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```
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`defineModel()` returns a ref that:
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- Syncs with parent's bound value
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- Emits `update:modelValue` when mutated
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### With Options
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```ts
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// Required model
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const model = defineModel<string>({ required: true })
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// With default
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const model = defineModel<number>({ default: 0 })
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```
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## Named v-model
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Use arguments for multiple v-models:
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```vue
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<!-- UserName.vue -->
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<script setup lang="ts">
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const firstName = defineModel<string>('firstName')
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const lastName = defineModel<string>('lastName')
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</script>
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<template>
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<input v-model="firstName" />
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<input v-model="lastName" />
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</template>
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```
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```vue-html
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<UserName
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v-model:first-name="first"
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v-model:last-name="last"
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/>
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```
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## v-model Modifiers
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Access and handle modifiers:
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```vue-html
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<MyComponent v-model.capitalize="text" />
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```
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```vue
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<script setup lang="ts">
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const [model, modifiers] = defineModel<string>()
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console.log(modifiers) // { capitalize: true }
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</script>
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```
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### Transform with Modifiers
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Use `get` and `set` options:
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```vue
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<script setup lang="ts">
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const [model, modifiers] = defineModel<string>({
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set(value) {
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if (modifiers.capitalize) {
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return value.charAt(0).toUpperCase() + value.slice(1)
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}
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return value
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}
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})
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</script>
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<template>
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<input v-model="model" />
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</template>
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```
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### Modifiers with Named v-model
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```vue-html
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<MyComponent v-model:title.capitalize="title" />
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```
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```ts
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const [title, titleModifiers] = defineModel<string>('title')
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console.log(titleModifiers) // { capitalize: true }
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```
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## Manual Implementation (Pre-3.4)
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Understanding what `defineModel` does under the hood:
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```vue
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<script setup lang="ts">
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const props = defineProps<{
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modelValue: string
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}>()
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const emit = defineEmits<{
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'update:modelValue': [value: string]
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}>()
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</script>
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<template>
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<input
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:value="props.modelValue"
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@input="emit('update:modelValue', ($event.target as HTMLInputElement).value)"
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/>
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</template>
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```
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For named v-model `v-model:title`:
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```ts
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defineProps<{ title: string }>()
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defineEmits<{ 'update:title': [value: string] }>()
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```
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## Typing defineModel
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```ts
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// Basic
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const model = defineModel<string>()
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// ^? Ref<string | undefined>
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// Required (removes undefined)
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const model = defineModel<string>({ required: true })
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// ^? Ref<string>
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// With modifiers
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const [model, modifiers] = defineModel<string, 'trim' | 'capitalize'>()
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// ^? Record<'trim' | 'capitalize', true | undefined>
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```
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## Warning: Default Values
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Having a default in `defineModel` without providing a value from parent causes desync:
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```vue
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<!-- Child: model is 1 -->
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<script setup>
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const model = defineModel({ default: 1 })
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</script>
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<!-- Parent: myRef is undefined -->
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<script setup>
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const myRef = ref()
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</script>
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<Child v-model="myRef" />
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```
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<!--
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Source references:
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- https://vuejs.org/guide/components/v-model.html
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- https://vuejs.org/api/sfc-script-setup.html#definemodel
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-->
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