vue2 elementui动态必填项

案例，选择类型值为是，控制内容必填，如果内容有值，内容的字数不小于3

<template>
  <div>
    <el-form :model="form" :rules="rules" ref="ruleForm" label-width="100px">
      <el-form-item label="类型" prop="type">
        <el-select v-model="form.type" placeholder="请选择类型">
          <el-option label="是" value="1"></el-option>
          <el-option label="否" value="2"></el-option>
        </el-select>
      </el-form-item>
      <!-- <el-form-item label="内容" :prop="form.type == '1' ? 'content' : ''"> -->
      <el-form-item label="内容" prop="content" :rules="[{required: form.type == '1', message: '必填'},{ pattern: /^.{3,}$/, message: '输入内容长度不能小于3', trigger: 'blur' } ]">
        <el-input v-model="form.content" placeholder="请输入内容"></el-input>
      </el-form-item>
      <el-form-item>
        <el-button type="primary" @click="submitForm('ruleForm')"
          >立即创建</el-button
        >
        <el-button @click="resetForm('ruleForm')">重置</el-button>
      </el-form-item>
    </el-form>
  </div>
</template>
<script>
export default {
  data() {
    return {
      form: {
        type: null,
        content: null,
      },
      rules: {
          type: [{ required: true, message: "必填", trigger: "blur" }],
        },
    };
  },
  methods: {
    submitForm(formName) {
      this.$refs[formName].validate((valid) => {
        if (valid) {
          alert("submit!");
        } else {
          console.log("error submit!!");
          return false;
        }
      });
    },
    resetForm(formName) {
      this.$refs[formName].resetFields();
    },
  },
};
</script>
<style scoped>
</style>

核心代码配置项

prop="content" 
:rules="[{required: form.type == '1', message: '必填'},{ pattern: /^.{3,}$/, message: '输入内容长度不能小于3', trigger: 'blur' } ]"

注意：在el-form-item标签上添加了rules，必须得添加上prop的属性和值才生效prop的值可以是任意的唯一值