gt-agent-company/.agents/skills/vue/references/components-v-model.md

name, description

name	description
component-v-model	Implement two-way data binding on custom components

Component v-model

Create two-way bindings between parent and child components.

defineModel() (3.4+, Recommended)

The simplest way to implement v-model:

<!-- Child.vue -->
<script setup lang="ts">
const model = defineModel<string>()
</script>

<template>
  <input v-model="model" />
</template>

<!-- Parent.vue -->
<Child v-model="searchText" />

defineModel() returns a ref that:

• Syncs with parent's bound value
• Emits update:modelValue when mutated

With Options

// Required model
const model = defineModel<string>({ required: true })

// With default
const model = defineModel<number>({ default: 0 })

Named v-model

Use arguments for multiple v-models:

<!-- UserName.vue -->
<script setup lang="ts">
const firstName = defineModel<string>('firstName')
const lastName = defineModel<string>('lastName')
</script>

<template>
  <input v-model="firstName" />
  <input v-model="lastName" />
</template>

<UserName
  v-model:first-name="first"
  v-model:last-name="last"
/>

v-model Modifiers

Access and handle modifiers:

<MyComponent v-model.capitalize="text" />

<script setup lang="ts">
const [model, modifiers] = defineModel<string>()

console.log(modifiers) // { capitalize: true }
</script>

Transform with Modifiers

Use get and set options:

<script setup lang="ts">
const [model, modifiers] = defineModel<string>({
  set(value) {
    if (modifiers.capitalize) {
      return value.charAt(0).toUpperCase() + value.slice(1)
    }
    return value
  }
})
</script>

<template>
  <input v-model="model" />
</template>

Modifiers with Named v-model

<MyComponent v-model:title.capitalize="title" />

const [title, titleModifiers] = defineModel<string>('title')
console.log(titleModifiers) // { capitalize: true }

Manual Implementation (Pre-3.4)

Understanding what defineModel does under the hood:

<script setup lang="ts">
const props = defineProps<{
  modelValue: string
}>()

const emit = defineEmits<{
  'update:modelValue': [value: string]
}>()
</script>

<template>
  <input
    :value="props.modelValue"
    @input="emit('update:modelValue', ($event.target as HTMLInputElement).value)"
  />
</template>

For named v-model v-model:title:

defineProps<{ title: string }>()
defineEmits<{ 'update:title': [value: string] }>()

Typing defineModel

// Basic
const model = defineModel<string>()
//    ^? Ref<string | undefined>

// Required (removes undefined)
const model = defineModel<string>({ required: true })
//    ^? Ref<string>

// With modifiers
const [model, modifiers] = defineModel<string, 'trim' | 'capitalize'>()
//            ^? Record<'trim' | 'capitalize', true | undefined>

Warning: Default Values

Having a default in defineModel without providing a value from parent causes desync:

<!-- Child: model is 1 -->
<script setup>
const model = defineModel({ default: 1 })
</script>

<!-- Parent: myRef is undefined -->
<script setup>
const myRef = ref()
</script>
<Child v-model="myRef" />