[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.

 1 // 总的全选
 2     handleSelectAllClassfiy(val) {
 3       if (val) {
 4         for (let i = 0; i < this.tabledata.length; i += 1) {
 5           this.tabledata[i].mychecked = true;
 6           this.firstChanged(i); // 调用一级change事件
 7         }
 8       } else {
 9         for (let i = 0; i < this.tabledata.length; i += 1) {
10           this.tabledata[i].mychecked = false;
11           this.firstChanged(i); // 调用一级change事件
12         }
13       }
14     },

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：

 1 allChecked: {
 2 　　get () {
 3       let count = 0;
 4       for (let i = 0; i < this.tabledata.length; i += 1) {
 5          if (this.tabledata[i].mychecked === true) {
 6             count += 1;
 7          } else {
 8             count -= 1;
 9          }
10       }
11       if (count === this.tabledata.length) {
12           return true;
13       }
14       return false;
15    },
16    set (val) {
17       return val;
18    }
19 }