vue3-04修改任务

步骤：

1. v-model为todo.title
2. 用一个响应式变量editingTodoRef来记录当前编辑的是哪一个todo，用editingTodoRef和当前的todo判读是否相等来设置编辑状态。
3. editTodo双击鼠标左键dblclick将当前的todo传递到editTodo并且将值赋给editingTodoRef。
4. 失去焦点或者按下enter键来doneEdit完成修改.
5. 按下esc键来取消编辑：在编辑前用一个变量originTitle来存储编辑前的值，cancelEdit取消编辑的时候将todo.title赋值为originTitle的值。
6. 页面有一个功能：allDoneRef全部完成的时候下拉箭头的颜色为深色，因此，需要通过判断todo的completed属性全为true。
7. setAllChecked设置为全部完成或者全部为不完成：如果页面传递过来的为true则为全完成，反之。

useEditTodo.js
import {
    ref,computed
} from "vue"
export default function useEditTodo(todosRef) {
    const editingTodoRef = ref(null); //当前正在修改哪一个todo
    let originTitle = null; //缓存编辑之前的title值,用于取消编辑

    // 鼠标左键双击
    const editTodo = (todo) => {
        originTitle = todo.title;
        editingTodoRef.value = todo;;
    }
    // 完成编辑
    const doneEdit = () => {
        editingTodoRef.value = null;
    }
    // 取消编辑
    const cancelEdit = (todo) => {
        editingTodoRef.value = null;
        todo.title = originTitle;
    }
    // 全部完成：已完成及为true页面的下拉箭头为深色
    const allDoneRef = computed(() => {
        const val = todosRef.value.filter((it) => !it.completed).length === 0;
        return val;
    })
    // 全选完成或全选未完成.参数checked为true或者false
    function setAllChecked(checked) {
        todosRef.value.forEach((todo) => {
            todo.completed = checked;
        })
    }

    return {
        editingTodoRef,
        editTodo,
        doneEdit,
        cancelEdit,
        allDoneRef,
        setAllChecked
    }
}

App.vue
<template>
  <link rel="stylesheet" href="./style.css" />
  <div id="app">
    <section class="todoapp">
      <header class="header">
        <h1>todos</h1>
        <input class="new-todo" autofocus="" autocomplete="off" placeholder="What needs to be done?" v-model="newTodoRef"
          @keyup.enter="addTodo" />
      </header>
      <section class="main">
        <input 
        id="toggle-all" 
        class="toggle-all" 
        type="checkbox"
        :checked="allDoneRef"
        @input="setAllChecked($event.target.checked)"
        />
        <label for="toggle-all">Mark all as complete</label>
        <ul class="todo-list">
          <li 
          class="todo" 
          v-for="todo in filteredTodosRef" 
          :key="todo.id" 
          :class="{ completed: todo.completed,editing:todo === editingTodoRef }">
            <div class="view">
              <input class="toggle" type="checkbox" v-model="todo.completed" />
              <!-- @dblclick鼠标左键双击事件 -->
              <label @dblclick="editTodo(todo)">{{ todo.title }}</label>
              <button class="destroy"></button>
            </div>
            <!-- 编辑状态 -->
            <input 
            class="edit" 
            type="text" 
            v-model="todo.title"
            @blur="doneEdit"
            @keyup.enter="doneEdit"
            @keyup.escape="cancelEdit(todo)"
            />
          </li>
        </ul>
      </section>
      <footer class="footer">
        <span class="todo-count">
          <strong>{{ remainingRef }}</strong>
          <span>item{{ remainingRef === 1 ? '' : 's' }} left</span>
        </span>
        <ul class="filters">
          <li><a href="#/all" :class="{ selected: visibilityRef === 'all' }">All</a></li>
          <li><a href="#/active" :class="{ selected: visibilityRef === 'active' }">Active</a></li>
          <li><a href="#/completed" :class="{ selected: visibilityRef === 'completed' }">Completed</a></li>
        </ul>
        <button class="clear-completed" v-show="completedRef">
          Clear completed
        </button>
      </footer>
    </section>
  </div>
</template>

<script>
import useTodoList from "./composition/useTodoList"
import useNewTodo from "./composition/useNewTodo"
import useFilter from "./composition/useFilter";
import useEditTodo from "./composition/useEditTodo";
export default {
  setup() {
    const { todosRef } = useTodoList();
    return {
      todosRef,
      ...useNewTodo(todosRef),
      ...useFilter(todosRef),
      ...useEditTodo(todosRef)
    }
  }
}
</script>