無法讀取未定義的屬性錯誤：Vue綁定物件屬性的類別綁定類型錯誤

Question

<p>我正在嘗試根據物件屬性綁定一個類，但是當我點擊列表物件觸發@click 時，控制台告訴我無法讀取isSelected 的物件屬性... 我正在嘗試在動態渲染的清單項目上使用函數來接收項目的id，並將此屬性設為false 或true 時觸發一個類別來啟動</p> <p>希望有人能告訴我下面的程式碼中我漏掉了什麼，謝謝 :)</p> <pre class="brush:php;toolbar:false;"><ul class="daysList"> <li v-for="day in January" v-bind:class="{addedToTrip: day.isSelected}" class="daynum" @click="toggleIsSelected(day)"daynum" @click="toggleIsSelected(day)"daynum:key=t; "day.id"> {{day.val}} </li> </ul></pre> <p>我的 vue 資料</p> <pre class="brush:php;toolbar:false;">data:function(){ return{ year: 2021, month: 1, day: 1, days:[18,19,20,21], January:[ {name: 'January', isSelected: false, id: 1, val:1}, {name: 'January', isSelected: false, id: 2, val:2}, {name: 'January', isSelected: false, id: 3, val:3}, {name: 'January', isSelected: false, id: 4, val:4}, {name: 'January', isSelected: false, id: 5, val:5}, {name: 'January', isSelected: false, id: 6, val:6}, {name: 'January', isSelected: false, id: 7, val:7}, {name: 'January', isSelected: false, id: 8, val:8}, {name: 'January', isSelected: false, id: 9, val:9}, {name: 'January', isSelected: false, id: 10, val:10}, {name: 'January', isSelected: false, id: 11, val:11}, {name: 'January', isSelected: false, id: 12, val:12}, {name: 'January', isSelected: false, id: 13, val:13}, {name: 'January', isSelected: false, id: 14, val:14}, {name: 'January', isSelected: false, id: 15, val:15}, {name: 'January', isSelected: false, id: 16, val:16}, {name: 'January', isSelected: false, id: 17, val:17}, {name: 'January', isSelected: false, id: 18, val:18}, {name: 'January', isSelected: false, id: 19, val:19}, {name: 'January', isSelected: false, id: 20, val:20}, {name: 'January', isSelected: false, id: 21, val:21}, {name: 'January', isSelected: false, id: 22, val:22}, {name: 'January', isSelected: false, id: 23, val:23}, {name: 'January', isSelected: false, id: 24, val:24}, {name: 'January', isSelected: false, id: 25, val:25}, {name: 'January', isSelected: false, id: 26, val:26}, {name: 'January', isSelected: false, id: 27, val:27}, {name: 'January', isSelected: false, id: 28, val:28}, {name: 'January', isSelected: false, id: 29, val:29}, {name: '一月', isSelected: false, id: 30, val:30}, {name: '一月', isSelected: false, id: 31, val:31}, ], 二月：[]， 行進：[]， 四月：[]， 可能：[]， 六月：[]， 七月：[]， 八月：[]， 九月：[]， 十月：[]， 十一月：[]， 十二月：[]， } },</pre> <p>評價 isSelected == true 時的 css 類別</p>

.addedToTrip{
    背景顏色：#2E9CFE；
    頂部邊框：.5px 純黑色；
    邊框底部：.5px 純黑色；
}</pre></p>            

Answer 1

在指定類別名稱時，你需要使用單引號

ul class="daysList">
  <li v-for="day in January" v-bind:class="{'addedToTrip': day.isSelected}" class="daynum" @click="toggleIsSelected(day)" :key="day.id"> // 改变 added
      {{day.val}}
  </li>
  </ul>