如何在vue的下拉列表中选择默认值时进行验证并显示消息

data() {
  return {
    selectedValue: '',
    validationMessage: ''
  }
}

<select v-model="selectedValue" v-on:change="validateSelection">
  <option value="">请选择</option>
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

methods: {
  validateSelection() {
    if (this.selectedValue === '') {
      this.validationMessage = '请选择一个选项'
    } else {
      this.validationMessage = ''
    }
  }
}

<div v-if="validationMessage" class="error-message">{{ validationMessage }}</div>