template部分:

  <!-- 修改弹窗 -->
  <el-dialog :title="dialogTxt" @close="closeDialog" :visible.sync="alertBox">
    <el-form ref="addForm" :rules="rules" :model="addForm" size="medium" label-width="100px">
      <el-row>
        <el-col :span="12">
          <el-form-item label="知识标题：" prop="knowledgeTitle">
            <el-input v-model="addForm.knowledgeTitle"></el-input>
          </el-form-item>
        </el-col>
        <el-col :span="12">
          <el-form-item label="内容：" prop="knowledgeContent">
            <el-input v-model="addForm.knowledgeContent"></el-input>
          </el-form-item>
        </el-col>

        <!-- 图片上传 -->
        <el-col :span=