element ui 数组类型form校验

循环数组生成的表单校验 prop需要用原数组加序号的方式来访问，否则会报：
 please transfer a valid prop path to form item! 

正确的prop写法： :prop="'courseResourceList.' + index + '.chapterTitle'" 
错误的prop写法：  :prop="item.chapterTitle" 或 prop="chapterTitle"

form表单数据结构如下：

      <div>
        <el-form :model="courseResourceForm" ref="courseResourceForm" label-position="right" label-width="120px">
          <el-row style="margin-bottom: 10px;">
            <el-col :span="24">上传课程资源</el-col>
          </el-row>
          <div v-for="(item, index) in courseResourceForm.courseResourceList" v-bind:key="item.courseResourceId" class="cardContainer">
            <el-form-item :label="item.chapterId">
              <upload-file :objAtmParams="item.videoParams" @onSuccess="uploadSuccess" @onRemove="afterDelete"></upload-file>
            </el-form-item>
            <el-form-item label="章节主题" :prop="'courseResourceList.' + index + '.chapterTitle'" :rules="{ required: true, message: '章节主题不能为空', trigger: 'blur' }">
              <el-input v-model="item.chapterTitle" style="width: 850px"></el-input>
            </el-form-item>
          </div>
        </el-form>
      </div>

  data () {
    return {
      courseId: '',
      courseResourceForm: {
        courseResourceList: [{
          chapterId: '',
          chapterTitle: '',
          videoParams: {
            atmLimit: 99, // 上传数量限制
            atmAccepts: '.mp4,.ppt,.pptx,.doc,.docx,.pdf', // 限制上传附件类型
            atmSize: 100,
            atmJobTypeCode: 'bsi_course_learn_video',
            objectId: '',
            fileList: [],
            listType: 'text' // 上传文件样式类型
          }
        }]
      }
    };
  }