下拉多选el-tag显示在输入框中

        <el-form-item label="项目分类" prop="ptId">
          <el-select
            v-model="showForm.ptId"
            multiple
            collapse-tags
            style="width:223px;"
            placeholder="请选择项目分类"
          >
            <el-option
              v-for="item in serviceClassOptions"
              :key="item.id"
              :label="item.productName"
              :disabled="item.disabled"
              :value="item.id"
            >
            </el-option>
          </el-select>
        </el-form-item>