javascript - Vue $refs 为什么无法获取组件对象

Question

<el-tree ref="permissions_tree" class="permissions-tree" :data="permissions" :props="basicConfig.defaultProps" show-checkbox node-key="id" :render-content="renderNode"></el-tree>

mounted () {
  console.log(this.$refs.permissions_tree);
}

在 mounted 中打印输出的是undefined！这是为什么？

我在表格中渲染的按钮，第一次点击调用 console.log(this.$refs.permissions_tree);得到的也是 undefined，第二次就能正常获取到组件了

{
    title: '操作',
    key: 'action',
    align: 'center',
    render: (h, params) => {
      return h('p', [
        h('Button', {
          props: {
            type: 'primary',
            size: 'small'
          },
          style: {
            marginRight: '5px'
          },
          on: {
            click: () => {
              this.userForm.staffid = params.row.staffid;
              this.userForm.name = params.row.name;
              this.userForm.phoneticize = params.row.phoneticize;
              this.userForm.gender = params.row.gender;
              this.userForm.mobile = params.row.mobile;
              this.userForm.telephone = params.row.telephone;
              this.userForm.identification = params.row.identification;
              this.userForm.positions = params.row.positions;
              this.userForm.permissions = params.row.permissions;
              this.userFormShow = true;
              console.log(this.$refs.permissions_tree); //这里
            }
          }
        }, '编辑')
      ]);
    }
}

Answer 1

可能你用v-if来切换组件展示，所以要在下一个tick才能获取到

this.$nextTick(() => {
    console.log(this.$refs.permissions_tree);
});

Answer 2

写在

this.$nextTick(() => {})

里试一下

Answer 3

外层组件是不是使用了v-if，换成v-show 试一下

Answer 4

调用这个方法
this.$nextTick(function () {

    // 里面打印
  })