Ⅰ. Pinia的介绍

Pinia官方网站

Pinia 是一个状态管理工具，Vue的专属状态管理库，它允许你跨组件或页面共享状态，让多个组件共享数据 。

那 Pinia 中存什么？

多个组件共享的数据 ，才存储在 Pinia 中
某个组件中的私有数据，依旧存储在组件自身内部

例如：

登陆的用户名需要在首页、个人中心页、搜索页、商品详情页使用，则用户名存储在 Pinia 中
新闻详情数据，只有在新闻详情页查看，则存储在组件自身内部

Ⅱ. Pinia的使用

一、例子准备

1. 目标

创建项目，为学习 Pinia 做准备

需求1：App.vue 作为根组件
需求2：子组件 Add 和子组件 Sub，作为在 App.vue 的子组件
需求3：三个组件共享库存数据（保持同步）

2. 效果

3. 代码示例

components/Add.vue文件：

<script setup></script>
 
<template>
  <div>
    <h3>Add组件</h3>
    <p>已知库存数: 0</p>
    <button>库存+1</button>
  </div>
</template>

components/Sub.vue文件：

<script setup></script>
 
<template>
  <div>
    <h3>Sub组件</h3>
    <p>已知库存数: 0</p>
    <button>库存-1</button>
  </div>
</template>

App.vue文件：

<script setup>
    import Add from '@/components/Add.vue'
    import Sub from '@/components/Sub.vue'
</script>
 
<template>
  <div>
    <h1>根组件</h1>
    <p>
      <span>库存总数: </span>
      <input type="number" />
    </p>
  </div>
  <hr />
  <Add />
  <hr />
  <Sub />
</template>
 
<style>
#app {
  width: 350px;
  margin: 60px auto;
  border: 1px solid #ccc;
  padding: 4px;
}
</style>

二、Pinia -- 准备store并渲染数据

1. 下载pinia

npm i pinia

2. 创建pinia实例并注册

main.js文件：

// 导入
import { createPinia } from 'pinia'
 
// 创建 pinia 实例
const pinia = **createPinia** ()
 
// 注册实例
**app.use(pinia)**

3. 定义仓库

创建 src/store/stock.js 文件，用来管理共享的库存数据。

defineStore 是 Pinia 定义仓库 的核心方法。语法如下所示：

import { defineStore } from 'pinia'
 
export const useXxxStore = **defineStore** (
  id: string,
  optionsOrSetup: Options | Setup
)

id(string)
- 仓库唯一标识符，通常是英文命名。
- 必填。Pinia 内部会用它来区分不同的 store。
- 示例：'user'、'cart'。

optionsOrSetup(Options | Setup) 有两种写法：

Options 对象式写法 （类似 Vuex）：

{
  state: () => ({ ... }),   // 定义响应式数据
  getters: { ... },         // 计算属性
  actions: { ... }          // 方法，可异步
}

Setup 函数式写法 （类似组合式 API）：

() => {
  const count = ref(0)
  const double = computed(() => count.value * 2)
  function increment() { count.value++ }
  return { count, double, increment }
}

useXxxStore：返回值，是一个函数。
- 在组件或逻辑中调用 useXxxStore() 就能拿到 store 实例。
- Store 实例包含你定义的 state、getter、action ，并且是响应式的。
- 命名规则：最好含有 store 的名字，且以 use开头，以 Store结尾。比如 useUserStore、useCartStore、useProductStore。

① 组合式API（Setup函数）

import { defineStore } from 'pinia'
import { ref, computed } from 'vue'
 
// 定义一个名为 stock的store 并导出
export const useStockStore = defineStore('stock', () => {
  // 初始化库存数据
  const stock = ref(20)
  
  // 计算库存的两倍
  const doubleStock = computed(() => {
    return stock.value * 2
  })
  
  // 增加
  const addStock = () => {
    stock.value++
  }
  
  // 减少
  const subStock = () => {
    stock.value--
  }
  
  // 返回共享数据和操作函数
  return {
    stock,
    doubleStock,
    addStock,
    subStock
  }
})

② 选项式API（Option对象）

import { defineStore } from 'pinia'
 
// 定义一个名为 stock的store 并导出
export const useStockStore = defineStore('stock', {
  // 共享数据
  state: () => ({
    // 库存初始值
    stock: 20
  }),
  
  // 基于共享数据的计算属性
  getters: {
    // 计算库存的两倍
    doubleStock: (state) => state.stock * 2
  },
  
  // 修改共享数据的方法
  actions: {
    // 增加库存
    addStock() {
      this.stock++
    },
    // 减少库存
    subStock() {
      this.stock--
    }
  }
})

4. 使用仓库

Add.vue文件：

<script setup>
    // 导入 使用库存仓库
    import { useStockStore } from '@/store/stock.js'
    
    // 创建库存仓库
    **const stockStore = useStockStore()** 
</script>
 
<template>
  <div>
    <h3>Add组件</h3>
    <p>已知库存数: {{ stockStore.stock }}</p>
    <button @click="stockStore.addStock()">库存+1</button>
  </div>
</template>

Sub.vue文件：

<script setup>
    // 导入 使用库存仓库
    import { useStockStore } from '@/store/stock.js'
    
    // 创建库存仓库
    **const stockStore = useStockStore()** 
</script>
 
<template>
  <div>
    <h3>Sub组件</h3>
    <p>已知库存数: {{ stockStore.stock }}</p>
    <button @click="stockStore.subStock()">库存-1</button>
  </div>
</template>

App.vue文件：

<script setup>
    import Add from './components/Add.vue'
    import Sub from './components/Sub.vue'
    import { useStockStore } from '@/store/stock'
    **const stockStore = useStockStore()** 
</script>
 
<template>
  <h1>根组件</h1>
  库存总数:
  <input
    type="number"
    v-model.number="stockStore.stock" />
  <p>stock 的翻倍值 = {{ stockStore.doubleStock }}</p>
  <hr />
  <Add />
  <hr />
  <Sub />
</template>
 
<style>
#app {
  width: 350px;
  margin: 100px auto;
  padding: 5px 10px;
  border: 1px solid #ccc;
}
</style>

Ⅲ. Pinia重构待办任务案例

components/TodoHeader.vue

<script setup></script>
 
<template>
  <header class="header">
    <h1>todos</h1>
    <input class="new-todo" placeholder="What needs to be finished?" autofocus />
  </header>
</template>

components/TodoMain.vue

<script setup></script>
 
<template>
  <section class="main">
    <input id="toggle-all" class="toggle-all" type="checkbox" />
    <label for="toggle-all">Mark all as complete</label>
    <ul class="todo-list">
      <li>
        <div class="view">
          <input class="toggle" type="checkbox" />
          <label>Buy eggs</label>
          <button class="destroy"></button>
        </div>
      </li>
      <li>
        <div class="view">
          <input class="toggle" type="checkbox" checked />
          <label>打王者</label>
          <button class="destroy"></button>
        </div>
      </li>
    </ul>
  </section>
</template>

components/TodoFooter.vue

<script setup></script>
 
<template>
  <footer class="footer">
    <span class="todo-count"><strong>0</strong> item left</span>
    <ul class="filters">
      <li>
        <a href="#/" class="selected">All</a>
      </li>
      <li>
        <a href="#/active">Active</a>
      </li>
      <li>
        <a href="#/completed">Completed</a>
      </li>
    </ul>
    <button class="clear-completed">
      Clear completed
    </button>
  </footer>
</template>

App.vue

<script setup>
    import './assets/style.css'
    import TodoHeader from './components/TodoHeader.vue'
    import TodoMain from './components/TodoMain.vue'
    import TodoFooter from './components/TodoFooter.vue'
</script>
 
<template>
  <section class="todoapp">
    <todo-header />
    <todo-main />
    <todo-footer />
  </section>
</template>

assets/style.css

@charset 'utf-8';
 
html,
body {
  margin: 0;
  padding: 0;
}
 
button {
  margin: 0;
  padding: 0;
  border: 0;
  background: none;
  font-size: 100%;
  vertical-align: baseline;
  font-family: inherit;
  font-weight: inherit;
  color: inherit;
  -webkit-appearance: none;
  appearance: none;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
 
body {
  font:
    14px 'Helvetica Neue',
    Helvetica,
    Arial,
    sans-serif;
  line-height: 1.4em;
  background: #f5f5f5;
  color: #111111;
  min-width: 230px;
  max-width: 550px;
  margin: 0 auto;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-weight: 300;
}
 
.hidden {
  display: none;
}
 
.todoapp {
  background: #fff;
  margin: 130px 0 40px 0;
  position: relative;
  box-shadow:
    0 2px 4px 0 rgba(0, 0, 0, 0.2),
    0 25px 50px 0 rgba(0, 0, 0, 0.1);
}
 
.todoapp input::-webkit-input-placeholder {
  font-style: italic;
  font-weight: 400;
  color: rgba(0, 0, 0, 0.4);
}
 
.todoapp input::-moz-placeholder {
  font-style: italic;
  font-weight: 400;
  color: rgba(0, 0, 0, 0.4);
}
 
.todoapp input::input-placeholder {
  font-style: italic;
  font-weight: 400;
  color: rgba(0, 0, 0, 0.4);
}
 
.todoapp h1 {
  position: absolute;
  top: -100px;
  width: 100%;
  font-size: 50px;
  font-weight: 200;
  text-align: center;
  color: #b83f45;
  -webkit-text-rendering: optimizeLegibility;
  -moz-text-rendering: optimizeLegibility;
  text-rendering: optimizeLegibility;
}
 
.new-todo,
.edit {
  position: relative;
  margin: 0;
  width: 100%;
  font-size: 24px;
  font-family: inherit;
  font-weight: inherit;
  line-height: 1.4em;
  color: inherit;
  padding: 6px;
  border: 1px solid #999;
  box-shadow: inset 0 -1px 5px 0 rgba(0, 0, 0, 0.2);
  box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
 
.new-todo {
  padding: 16px 16px 16px 60px;
  height: 65px;
  border: none;
  background: rgba(0, 0, 0, 0.003);
  box-shadow: inset 0 -2px 1px rgba(0, 0, 0, 0.03);
}
 
.main {
  position: relative;
  z-index: 2;
  border-top: 1px solid #e6e6e6;
}
 
.toggle-all {
  width: 1px;
  height: 1px;
  border: none; /* Mobile Safari */
  opacity: 0;
  position: absolute;
  right: 100%;
  bottom: 100%;
}
 
.toggle-all + label {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 45px;
  height: 65px;
  font-size: 0;
  position: absolute;
  top: -65px;
  left: -0;
}
 
.toggle-all + label:before {
  content: '';
  display: inline-block;
  font-size: 22px;
  color: #949494;
  padding: 10px 27px 10px 27px;
  -webkit-transform: rotate(90deg);
  transform: rotate(90deg);
}
 
.toggle-all:checked + label:before {
  color: #484848;
}
 
.todo-list {
  margin: 0;
  padding: 0;
  list-style: none;
}
 
.todo-list li {
  position: relative;
  font-size: 24px;
  border-bottom: 1px solid #ededed;
}
 
.todo-list li:last-child {
  border-bottom: none;
}
 
.todo-list li.editing {
  border-bottom: none;
  padding: 0;
}
 
.todo-list li.editing .edit {
  display: block;
  width: calc(100% - 43px);
  padding: 12px 16px;
  margin: 0 0 0 43px;
}
 
.todo-list li.editing .view {
  display: none;
}
 
.todo-list li .toggle {
  text-align: center;
  width: 40px;
  /* auto, since non-WebKit browsers doesn't support input styling */
  height: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  margin: auto 0;
  border: none; /* Mobile Safari */
  -webkit-appearance: none;
  appearance: none;
}
 
.todo-list li .toggle {
  opacity: 0;
}
 
.todo-list li .toggle + label {
  /*
  Firefox requires `#` to be escaped -
  https://bugzilla.mozilla.org/show_bug.cgi?id=922433
  IE and Edge requires *everything* to be escaped to render, so we do that
  instead of just the `#` - https://developer.microsoft.com/en-us/microsoft-
  edge/platform/issues/7157459/
  */
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23949494%22%20stroke-width%3D%223%22/%3E%3C/svg%3E');
  background-repeat: no-repeat;
  background-position: center left;
}
 
.todo-list li .toggle:checked + label {
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%2359A193%22%20stroke-width%3D%223%22%2F%3E%3Cpath%20fill%3D%22%233EA390%22%20d%3D%22M72%2025L42%2071%2027%2056l-4%204%2020%2020%2034-52z%22%2F%3E%3C%2Fsvg%3E');
}
 
.todo-list li label {
  overflow-wrap: break-word;
  padding: 15px 15px 15px 60px;
  display: block;
  line-height: 1.2;
  transition: color 0.4s;
  font-weight: 400;
  color: #484848;
}
 
.todo-list li.completed label {
  color: #949494;
  text-decoration: line-through;
}
 
.todo-list li .destroy {
  display: none;
  position: absolute;
  top: 0;
  right: 10px;
  bottom: 0;
  width: 40px;
  height: 40px;
  margin: auto 0;
  font-size: 30px;
  color: #949494;
  transition: color 0.2s ease-out;
}
 
.todo-list li .destroy:hover,
.todo-list li .destroy:focus {
  color: #c18585;
}
 
.todo-list li .destroy:after {
  content: '×';
  display: block;
  height: 100%;
  line-height: 1.1;
}
 
.todo-list li:hover .destroy {
  display: block;
}
 
.todo-list li .edit {
  display: none;
}
 
.todo-list li.editing:last-child {
  margin-bottom: -1px;
}
 
.footer {
  padding: 10px 15px;
  height: 20px;
  text-align: center;
  font-size: 15px;
  border-top: 1px solid #e6e6e6;
}
 
.footer:before {
  content: '';
  position: absolute;
  right: 0;
  bottom: 0;
  left: 0;
  height: 50px;
  overflow: hidden;
  box-shadow:
    0 1px 1px rgba(0, 0, 0, 0.2),
    0 8px 0 -3px #f6f6f6,
    0 9px 1px -3px rgba(0, 0, 0, 0.2),
    0 16px 0 -6px #f6f6f6,
    0 17px 2px -6px rgba(0, 0, 0, 0.2);
}
 
.todo-count {
  float: left;
  text-align: left;
}
 
.todo-count strong {
  font-weight: 300;
}
 
.filters {
  margin: 0;
  padding: 0;
  list-style: none;
  position: absolute;
  right: 0;
  left: 0;
}
 
.filters li {
  display: inline;
}
 
.filters li a {
  color: inherit;
  margin: 3px;
  padding: 3px 7px;
  text-decoration: none;
  border: 1px solid transparent;
  border-radius: 3px;
}
 
.filters li a:hover {
  border-color: #db7676;
}
 
.filters li a.selected {
  border-color: #ce4646;
}
 
.clear-completed,
html .clear-completed:active {
  float: right;
  position: relative;
  line-height: 19px;
  text-decoration: none;
  cursor: pointer;
}
 
.clear-completed:hover {
  text-decoration: underline;
}
 
.info {
  margin: 65px auto 0;
  color: #4d4d4d;
  font-size: 11px;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.5);
  text-align: center;
}
 
.info p {
  line-height: 1;
}
 
.info a {
  color: inherit;
  text-decoration: none;
  font-weight: 400;
}
 
.info a:hover {
  text-decoration: underline;
}
 
/*
Hack to remove background from Mobile Safari.
Can't use it globally since it destroys checkboxes in Firefox
*/
@media screen and (-webkit-min-device-pixel-ratio: 0) {
  .toggle-all,
  .todo-list li .toggle {
    background: none;
  }
 
  .todo-list li .toggle {
    height: 40px;
  }
}
 
@media (max-width: 430px) {
  .footer {
    height: 50px;
  }
 
  .filters {
    bottom: 10px;
  }
}
 
:focus,
.toggle:focus + label,
.toggle-all:focus + label {
  box-shadow: 0 0 2px 2px #cf7d7d;
  outline: 0;
}

完整代码

https://github.com/lirendada/Front-end-learning/tree/main/25_7_21_vue-engineering-way/src/09-Pinia%EF%BC%9Avue3%E7%8A%B6%E6%80%81%E7%AE%A1%E7%90%86/2.%E4%BB%BB%E5%8A%A1%E6%A1%88%E4%BE%8B%E9%87%8D%E6%9E%84

Pinia：vue3状态管理