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

阅读这篇文章：https://blog.csdn.net/weixin_34090562/article/details/91369638

全选，通过计算属性计算得来。结果报错Computed property "XXX" was assigned to but it has no setter.

// 总的全选
    handleSelectAllClassfiy(val) {
      if (val) {
        for (let i = 0; i < this.tabledata.length; i += 1) {
          this.tabledata[i].mychecked = true;
          this.firstChanged(i); // 调用一级change事件
        }
      } else {
        for (let i = 0; i < this.tabledata.length; i += 1) {
          this.tabledata[i].mychecked = false;
          this.firstChanged(i); // 调用一级change事件
        }
      }
    },

 除了获取计算属性的值，还可以设置计算属性的值，并且在设置过程中做一些操作。实现这一点需要将计算属性由函数改为带有get和set属性的对象。

解决方法：

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;
   }
}