情景描述：
el-form 的ref=“obj” rules 对象obj有a,b,c三个字段，点击按钮a，a和b字段必填,点击按钮c,c字段必填，如何通过 this.$refs.obj.validate((valid)=>{})去判断呢

<template><div><!-- 你的表单组件 --><el-form ref="obj" :model="obj" :rules="updatedRules"><!-- 表单字段 --><el-form-item prop="a" label="字段 a"><el-input v-model="obj.a"></el-input></el-form-item><el-form-item prop="b" label="字段 b"><el-input v-model="obj.b"></el-input></el-form-item><el-form-item prop="c" label="字段 c"><el-input v-model="obj.c"></el-input></el-form-item><el-button type="primary" @click="submitFormAB('obj')">Submit</el-button><el-button type="primary" @click="submitFormC('obj')">Submit</el-button></el-form></div>
</template><script>
export default {data(){return {updatedRules：{}}},watch: {updatedRules: {handler(newVal, oldVal) {// 如果需要，可以在这里处理 rules 变化的逻辑console.log('Rules 发生变化:', newVal);},immediate: true // 组件挂载时立即触发}}，methods:{submitFormAB(formData){this.$nextTick(() => {  //这里注意使用了 $nextTick 以便于渲染dom// 动态更新验证规则后重置表单验证状态this.$refs[formData].clearValidate();// 更新完规则后执行验证--备注一下代码// this.$refs.obj.validate();});this.updatedRules = {a: [{ required: true, message: '字段 a 必填', trigger: 'blur' }],b: [{ required: true, message: '字段 b 必填', trigger: 'blur' }]};this.$resf[formData].validate((valid)=>{if(valid){//验证完之后调接口}})},submitFormC(formData){this.$nextTick(() => {// 动态更新验证规则后重置表单验证状态this.$refs[formData].clearValidate();});this.updatedRules = {c: [{ required: true, message: '字段 c 必填', trigger: 'blur' }]};this.$resf[formData].validate((valid)=>{if(valid){//验证完之后调接口}})},}};
</script>