Vue3 provide/inject用法总结

1. 基本概念

provide/inject 是 Vue3 中实现跨层级组件通信的方案，类似于 React 的 Context。它允许父组件向其所有子孙组件注入依赖，无论层级有多深。

1.1 基本语法

// 提供方（父组件）
const value = ref('hello')
provide('key', value)// 注入方（子孙组件）
const value = inject('key')

2. 基础用法

2.1 提供静态值

<!-- Parent.vue -->
<script setup>
import { provide } from 'vue'// 提供静态值
provide('theme', 'dark')
provide('language', 'zh-CN')
</script><!-- Child.vue -->
<script setup>
import { inject } from 'vue'// 注入值
const theme = inject('theme')
const language = inject('language')
</script><template><div :class="theme"><p>Current Language: {{ language }}</p></div>
</template>

2.2 提供响应式数据

<!-- Parent.vue -->
<script setup>
import { provide, ref } from 'vue'const count = ref(0)
const updateCount = () => {count.value++
}// 提供响应式数据和更新方法
provide('count', {count,updateCount
})
</script><!-- Child.vue -->
<script setup>
import { inject } from 'vue'const { count, updateCount } = inject('count')
</script><template><div><p>Count: {{ count }}</p><button @click="updateCount">Increment</button></div>
</template>

3. 进阶用法

3.1 使用 Symbol 作为 key

// injection-keys.ts
export const COUNT_KEY = Symbol('count')
export const THEME_KEY = Symbol('theme')

<!-- Parent.vue -->
<script setup lang="ts">
import { provide } from 'vue'
import { COUNT_KEY, THEME_KEY } from './injection-keys'const count = ref(0)
provide(COUNT_KEY, count)
provide(THEME_KEY, 'dark')
</script><!-- Child.vue -->
<script setup lang="ts">
import { inject } from 'vue'
import { COUNT_KEY, THEME_KEY } from './injection-keys'const count = inject(COUNT_KEY)
const theme = inject(THEME_KEY)
</script>

3.2 提供默认值

<script setup>
import { inject } from 'vue'// 使用静态默认值
const theme = inject('theme', 'light')// 使用工厂函数作为默认值
const now = inject('timestamp', () => Date.now())
</script>

3.3 只读数据

<!-- Parent.vue -->
<script setup>
import { provide, ref, readonly } from 'vue'const count = ref(0)
// 提供只读版本，防止子组件修改
provide('count', readonly(count))// 提供更新方法
provide('updateCount', () => {count.value++
})
</script><!-- Child.vue -->
<script setup>
import { inject } from 'vue'const count = inject('count')
const updateCount = inject('updateCount')
</script>

4. 实际应用场景

4.1 主题系统

<!-- ThemeProvider.vue -->
<script setup>
import { provide, ref } from 'vue'const theme = ref('light')
const toggleTheme = () => {theme.value = theme.value === 'light' ? 'dark' : 'light'
}provide('theme', {theme,toggleTheme
})
</script><template><div :class="theme.value"><slot></slot></div>
</template><!-- 使用组件 -->
<script setup>
import { inject } from 'vue'const { theme, toggleTheme } = inject('theme')
</script><template><button @click="toggleTheme">Switch to {{ theme === 'light' ? 'dark' : 'light' }} mode</button>
</template>

4.2 多语言系统

<!-- I18nProvider.vue -->
<script setup>
import { provide, ref } from 'vue'const locale = ref('en')
const messages = {en: {greeting: 'Hello',farewell: 'Goodbye'},zh: {greeting: '你好',farewell: '再见'}
}const t = (key) => messages[locale.value][key]
const setLocale = (lang) => {locale.value = lang
}provide('i18n', {locale,t,setLocale
})
</script><!-- 使用组件 -->
<script setup>
import { inject } from 'vue'const { t, setLocale, locale } = inject('i18n')
</script><template><div><select v-model="locale"><option value="en">English</option><option value="zh">中文</option></select><p>{{ t('greeting') }}</p></div>
</template>

4.3 状态管理

<!-- Store.vue -->
<script setup>
import { provide, reactive } from 'vue'const store = reactive({user: null,todos: [],addTodo(text) {this.todos.push({ id: Date.now(), text, completed: false })},toggleTodo(id) {const todo = this.todos.find(t => t.id === id)if (todo) {todo.completed = !todo.completed}}
})provide('store', store)
</script><!-- TodoList.vue -->
<script setup>
import { inject } from 'vue'const store = inject('store')
</script><template><div><inputv-model="newTodo"@keyup.enter="store.addTodo(newTodo)"><ul><liv-for="todo in store.todos":key="todo.id"@click="store.toggleTodo(todo.id)">{{ todo.text }}</li></ul></div>
</template>

5. TypeScript 支持

5.1 类型定义

// types.ts
export interface ThemeContext {theme: Ref<'light' | 'dark'>toggleTheme: () => void
}export const ThemeSymbol = Symbol('theme')

5.2 带类型的 provide/inject

<script setup lang="ts">
import { provide, inject } from 'vue'
import { ThemeContext, ThemeSymbol } from './types'// 提供方
provide<ThemeContext>(ThemeSymbol, {theme: ref('light'),toggleTheme: () => { /* ... */ }
})// 注入方
const theme = inject<ThemeContext>(ThemeSymbol)
</script>

6. 最佳实践

使用 Symbol 作为 key

const MyKey = Symbol('my-key')
provide(MyKey, value)

提供只读数据
```
provide('data', readonly(data))
```

集中管理 injection key

// keys.ts
export const THEME_KEY = Symbol('theme')
export const I18N_KEY = Symbol('i18n')

使用组合式函数封装

// useTheme.ts
export function useTheme() {const theme = inject(THEME_KEY)if (!theme) {throw new Error('useTheme must be used within ThemeProvider')}return theme
}