业务场景：根据form表单中的某些下拉框选中值，动态切换一些属性的必填校验。

<template>
  <div>
    <el-form :model="ruleForm" :rules="rules" ref="ruleForm" label-width="100px" class="demo-ruleForm">
      <el-form-item label="活动名称" prop="name" :required="isHaveTo">
        <el-input v-model="ruleForm.name"></el-input>
      </el-form-item>
      <el-form-item label="活动区域" prop="region">
        <el-select v-model="ruleForm.region" placeholder="请选择活动区域" style="width:100%">
          <el-option label="必填" value="0"></el-option>
          <el-option label="非必填" value="1"></el-option>
        </el-select>
      </el-form-item>
      <el-form-item>
        <el-button type="primary" @click="submitForm('ruleForm')">立即创建</el-button>
      </el-form-item>
    </el-form>
  </div>
</template>
<script>
export default {
  name: 'HelloWorld',
  data() {
    // 验证活动名称的函数
    let validateName = (rule, value, callback) => {
      // 当活动名称为空值且为必填时，抛出错误，反之通过校验
      if (this.ruleForm.name === '' && this.isHaveTo) {
        callback(new Error('请输入活动名称'))
      } else {
        callback()
      }
    }
    return {
      ruleForm: {
        name: '',
        region: ''
      },
      rules: {
        name: [{ validator: validateName }],
        region: [{ required: true, message: '请选择类型', trigger: 'blur' }]
      }
    }
  },
  computed: {
    isHaveTo: function() {
      return this.ruleForm.region !== `1`
    }
  },
  methods: {
    submitForm(formName) {
      this.$refs[formName].validate(valid => {
        if (valid) {
          console.log(`已提交表单`)
        } else {
          console.log('error submit!!')
          return false
        }
      })
    }
  }
}
</script>

效果图：
当活动区域非必填时，活动名称取消必填校验，否则活动名称必填。