[Vue] Computed property "XXX" was assigned to but it has no setter.

閱讀這篇文章：https://blog.csdn.net/weixin_34090562/article/details/91369638

全選，通過計算屬性計算得來。結果報錯Computed property "XXX" was assigned to but it has no setter.

// 總的全選
    handleSelectAllClassfiy(val) {
      if (val) {
        for (let i = 0; i < this.tabledata.length; i += 1) {
          this.tabledata[i].mychecked = true;
          this.firstChanged(i); // 調用一級change事件
        }
      } else {
        for (let i = 0; i < this.tabledata.length; i += 1) {
          this.tabledata[i].mychecked = false;
          this.firstChanged(i); // 調用一級change事件
        }
      }
    },

 除了獲取計算屬性的值，還可以設置計算屬性的值，並且在設置過程中做一些操作。實現這一點需要將計算屬性由函數改為帶有get和set屬性的對象。

解決方法：

allChecked: {
　　get () {
      let count = 0;
      for (let i = 0; i < this.tabledata.length; i += 1) {
         if (this.tabledata[i].mychecked === true) {
            count += 1;
         } else {
            count -= 1;
         }
      }
      if (count === this.tabledata.length) {
          return true;
      }
      return false;
   },
   set (val) {
      return val;
   }
}