3.7. Todo-List 案例

组件化编码流程

拆分静态组件：组件要按照功能点拆分，命名不要与html元素冲突
实现动态组件：考虑好数据的存放位置，数据是一个组件在用，还是一些组件在用
1. 一个组件在用：放在组件自身即可
2. 一些组件在用：放在他们共同的父组件上（状态提升）
实现交互：从绑定事件开始

props适用于

父组件 ==> 子组件通信
子组件 ==> 父组件通信（要求父组件先给子组件一个函数）

使用v-model时要切记：v-model绑定的值不能是props传过来的值，因为props是不可以修改的 props传过来的若是对象类型的值，修改对象中的属性时Vue不会报错，但不推荐这样做

src/App.vue

<template>
    <div id="root"> 
        <div class="todo-container"> 
            <div class="todo-wrap">
                <MyHeader :addTodo="addTodo"/>
                <MyList :todos="todos" :checkTodo="checkTodo" :deleteTodo="deleteTodo"/>
                <MyFooter :todos="todos" :checkAllTodo="checkAllTodo" :clearAllTodo="clearAllTodo"/>
            </div>
        </div>
    </div>
</template> 

<script> 
    // 引入组件
    import MyFooter from './components/MyFooter';
    import MyHeader from './components/MyHeader';
    import MyList from './components/MyList';

    export default { 
        name:'App', 
        components:{
            MyFooter,
            MyHeader,
            MyList
        },
        data() {
            return {
                todos:[
                    {id:'001',title:'抽烟',done:true},
                    {id:'002',title:'喝酒',done:false},
                    {id:'003',title:'开车',done:true}
                ]
            }
        },
        methods: {
            // 添加一个todo
            addTodo(todoObj) {
                this.todos.unshift(todoObj);
            },
            // 勾选or取消勾选一个todo
            checkTodo(id) {
                this.todos.forEach((todo)=>{
                    if(todo.id === id) todo.done = !todo.done;
                });
            },
            // 删除一个todo
            deleteTodo(id) {
                this.todos = this.todos.filter( todo => todo.id !== id )
            },
            // 全选or取消全选 
            checkAllTodo(done){
                this.todos.forEach((todo)=>{
                    todo.done = done;
                });
            },
            // 清除所有已经完成的todo
            clearAllTodo(){
                this.todos = this.todos.filter((todo)=>{
                    return !todo.done;
                })
            }
        }
    }
</script>

<style>
    body {
        background: #fff;
    }
    .btn {
        display: inline-block;
        padding: 4px 12px;
        margin-bottom: 0;
        font-size: 14px;
        line-height: 20px;
        text-align: center;
        vertical-align: middle;
        cursor: pointer;
        box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
        border-radius: 4px;
    }
    .btn-danger {
        color: #fff;
        background-color: #da4f49;
        border: 1px solid #bd362f;
    }
    .btn-danger:hover {
        color: #fff;
        background-color: #bd362f;
    }
    .btn:focus {
        outline: none;
    } 
    .todo-container {
        width: 600px;
        margin: 0 auto;
    }
    .todo-container .todo-wrap {
        padding: 10px;
        border: 1px solid #ddd;
        border-radius: 5px;
    }
</style>

src/components/MyHeader.vue

<template>
    <div class="todo-header">
        <input type="text" placeholder="请输入你的任务名称，按回车键确认" v-model="title" @keyup.enter="add"/> 
    </div>
</template>

<script>
    import {nanoid} from 'nanoid';
    
    export default {
        name: "Header",
        props:['addTodo'], // 接收从App传递过来的addTodo
        data(){
            return {
                title:'' // 收集用户输入的title
            }
        },
        methods: {
            add(){
                // 校验数据
                if(!this.title.trim()) return alert('输入不能为空')
                // 将用户的输入包装成一个todo对象
                const todoObj = { 
                    id: nanoid(), 
                    title:this.title, 
                    done:false 
                };
                // 通知App组件去添加一个todo对象
                this.addTodo(todoObj);
                // 清空输入
                this.title = '';
            }
        }
    }
</script>

<style scoped>
    .todo-header input {
        width: 560px;
        height: 28px;
        font-size: 14px;
        border: 1px solid #ccc;
        border-radius: 4px;
        padding: 4px 7px;
    }
    .todo-header input:focus {
        outline: none;
        border-color: rgba(82, 168, 236, 0.8);
        box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(82, 168, 236, 0.6);
    }
</style>

src/components/MyList.vue

<template>
    <ul class="todo-main">
        <MyItem v-for="todoObj in todos" :key="todoObj.id" :todo="todoObj" :checkTodo="checkTodo" :deleteTodo="deleteTodo"/>
    </ul>
</template>

<script>
    import MyItem from './MyItem';
    
    export default {
        name: "List",
        components: {
            MyItem
        },
        props:['todos', 'checkTodo', 'deleteTodo']
    }
</script>

<style scoped>
    .todo-main {
        margin-left: 0px;
        border: 1px solid #ddd;
        border-radius: 2px;
        padding: 0px;
    }
    .todo-empty {
        height: 40px;
        line-height: 40px;
        border: 1px solid #ddd; 
        border-radius: 2px;
        padding-left: 5px;
        margin-top: 10px;
    }
</style>

src/components/MyItem.vue

<template>
    <li>
       <label>
           <!-- 如下代码也能实现功能，但是不太推荐，因为有点违反原则，因为修改了props -->
           <!-- <input type="checkbox" v-model="todo.done"/> -->
           <input type="checkbox" :checked="todo.done" @change="handleCheck(todo.id)">
           <span>{{todo.title}}</span>
       </label>
        <button class="btn btn-danger" @click="handleDelete(todo.id)">删除</button>
    </li>
</template>

<script>
    export default {
        name: "Item",
        // 声明接收todo、checkTodo、deleteTodo
        props:['todo','checkTodo', 'deleteTodo'],
        methods: {
            // 勾选or取消勾选
            handleCheck(id) {
                // 通知App组件将对应的todo对象的done值取反
                this.checkTodo(id);
            },
            // 删除
            handleDelete(id){
                if(confirm('确定删除吗？')) {
                    this.deleteTodo(id); // 通知App组件将对应的todo对象删除
                }
            }
        }
    }
</script>

<style scoped>
    li {
        list-style: none;
        height: 36px;
        line-height: 36px;
        padding: 0 5px; 
        border-bottom: 1px solid #ddd;
    } 
    li label {
        float: left;
        cursor: pointer;
    }
    li label li input {
        vertical-align:middle; 
        margin-right:6px; 
        position:relative;
        top: -1px;
    } 
    li button {
        float: right;
        display: none;
        margin-top: 3px;
    }
    li:before {
        content: initial;
    } 
    li:last-child {
        border-bottom: none;
    } 
    li:hover{
        background-color: #ddd;
    }
    li:hover button{
        display: block;
    }
</style>

src/components/MyFooter.vue

<template>
    <div class="todo-footer" v-show="total">
        <label>
            <input type="checkbox" v-model="isAll"/>
        </label>
        <span>
            <span>已完成{{doneTotal}}</span> / 全部{{total}}
        </span>
        <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
    </div>
</template>

<script>
    export default {
        name: "Footer",
        props: ['todos', 'checkAllTodo', 'clearAllTodo'],
        computed: {
            // 总数
            total() {
              return this.todos.length;  
            },
            // 已完成数
            doneTotal() {
                // 此处使用reduce方法做条件统计
                return this.todos.reduce((pre, todo) => pre + (todo.done ? 1 : 0), 0);
            },
            // 控制全选框
            isAll:{
                // 全选框是否勾选
                get(){
                    return this.doneTotal === this.total && this.total > 0;
                },
                // isAll被修改时set被调用
                set(value){
                    this.checkAllTodo(value);
                }
            }
        },
        methods: {
            clearAll() {
                this.clearAllTodo();
            }
        }
    }
</script>

<style scoped>
    .todo-footer {
        height: 40px;
        line-height: 40px;
        padding-left: 6px;
        margin-top: 5px;
    }
    .todo-footer label {
        display: inline-block;
        margin-right: 20px;cursor: pointer;
    }
    .todo-footer label input {
        position: relative;
        top: -1px;
        vertical-align: middle; 
        margin-right: 5px;
    }
    .todo-footer button {
        float: right;
        margin-top: 5px;
    }
</style>