Element-UI中Select选择器 单选 多选问题 <el-select>

<template>
  <div class="app-container">
    <!--工具栏-->
    <div class="head-container">
      <div v-if="crud.props.searchToggle">
        <!-- 搜索 -->
        <label class="el-form-item-label">分类名称</label>
        <el-input v-model="query.name" clearable placeholder="分类名称" style=" 185px;" class="filter-item" @keyup.enter.native="crud.toQuery" />
        <date-range-picker
          v-model="query.createDate"
          start-placeholder="创建开始时间"
          end-placeholder="创建结束时间"
          class="date-item"
        />
        <rrOperation :crud="crud" />
      </div>
      <!--如果想在工具栏加入更多按钮，可以使用插槽方式， slot = 'left' or 'right'-->
      <crudOperation :permission="permission" />
      <!--表单组件-->
      <el-dialog :close-on-click-modal="false" :before-close="crud.cancelCU" :visible.sync="crud.status.cu > 0" :title="crud.status.title" width="500px">
        <el-form ref="form" :model="form" :rules="rules" size="small" label-width="80px">
          <el-form-item label="一级分类" prop="parent">
            <!-- multiple  在 el-select 中加这个属性是多选  不加是单选-->
            <el-select
              v-model="form.parents"
              style=" 178px"
              placeholder="请选择"
              @remove-tag="deleteTag"
              @change="changeCtegory"
            >
              <el-option
                v-for="item in parents"
                :key="item.name"
                :label="item.name"
                :value="item.id"
              />
            </el-select>
          </el-form-item>
          <el-form-item label="分类名称" prop="name">
            <el-input v-model="form.name" style=" 370px;" />
          </el-form-item>
        </el-form>
        <div slot="footer" class="dialog-footer">
          <el-button type="text" @click="crud.cancelCU">取消</el-button>
          <el-button :loading="crud.cu === 2" type="primary" @click="crud.submitCU">确认</el-button>
        </div>
      </el-dialog>
      <!--表格渲染-->
      <el-table ref="table" v-loading="crud.loading" :data="crud.data" size="small" style=" 100%;" @selection-change="crud.selectionChangeHandler">
        <el-table-column type="selection" width="55" />
        <el-table-column prop="id" label="id" />
        <el-table-column :show-overflow-tooltip="true" prop="parent" label="一级分类">
          <template slot-scope="scope">
            <div>{{ scope.row.parent==null ?"": scope.row.parent.name }}</div>
          </template>
        </el-table-column>
        <el-table-column prop="name" label="二级分类" />
        <el-table-column prop="updateTime" label="更新时间">
          <template slot-scope="scope">
            <span>{{ parseTime(scope.row.updateTime) }}</span>
          </template>
        </el-table-column>
        <el-table-column prop="createDate" label="创建时间">
          <template slot-scope="scope">
            <span>{{ parseTime(scope.row.createDate) }}</span>
          </template>
        </el-table-column>
        <el-table-column prop="available" label="是否可用" />
        <el-table-column v-permission="['admin','itemCategory:edit','itemCategory:del']" label="操作" width="150px" align="center">
          <template slot-scope="scope">
            <udOperation
              :data="scope.row"
              :permission="permission"
            />
          </template>
        </el-table-column>
      </el-table>
      <!--分页组件-->
      <pagination />
    </div>
  </div>
</template>

<script>
import crudItemCategory from '@/api/itemCategory'
import CRUD, { presenter, header, form, crud } from '@crud/crud'
import rrOperation from '@crud/RR.operation'
import crudOperation from '@crud/CRUD.operation'
import udOperation from '@crud/UD.operation'
import pagination from '@crud/Pagination'
import DateRangePicker from '@/components/DateRangePicker'
import { getAllCategory } from '@/api/itemCategory'
let userParents = []
const defaultForm = { id: null, parent: null, parent_id: null, name: null }
export default {
  name: 'ItemCategory',
  components: { pagination, crudOperation, rrOperation, udOperation, DateRangePicker },
  mixins: [presenter(), header(), form(defaultForm), crud()],
  cruds() {
    return CRUD({ title: '分类信息', url: 'api/itemCategory', sort: 'id,desc', crudMethod: { ...crudItemCategory }})
  },
  data() {
    return {
      parents: [],
      permission: {
        add: ['admin', 'itemCategory:add'],
        edit: ['admin', 'itemCategory:edit'],
        del: ['admin', 'itemCategory:del']
      },
      rules: {
        name: [
          { required: true, message: '分类名称不能为空', trigger: 'blur' }
        ]
      },
      queryTypeOptions: [
        { key: 'name', display_name: '分类名称' }
      ]
    }
  },

  methods: {
    // 钩子：在获取表格数据之前执行，false 则代表不获取数据
    [CRUD.HOOK.beforeRefresh]() {
      return true
    },
    // 多选
    changeCtegory(value) {
      userParents = []
      value.forEach(function(data, index) {
        const role = { id: data }
        userParents.push(role)
      })
    },
    // 单选
    // changeCtegory(value) {
    //   userParents = []
    //   const role = { id: value }
    //   userParents.push(role)
    // },
    deleteTag(value) {
      userParents.forEach(function(data, index) {
        if (data.id === value) {
          userParents.splice(index, value)
        }
      })
    },
    // 新增与编辑前做的操作
    [CRUD.HOOK.afterToCU](crud, form) {
      this.getCategorys()
    },
    // 提交前做的操作
    [CRUD.HOOK.afterValidateCU](crud) {
      crud.form.parent = userParents[0]
      return true
    },
    // 获取弹窗内数据
    getCategorys() {
      getAllCategory().then(res => {
        this.parents = res
      }).catch(() => { })
    }
  }
}
</script>

<style scoped>

</style>

 @PostMapping
    @Log("新增分类信息")
    @ApiOperation("新增分类信息")
    @PreAuthorize("@el.check('itemCategory:add')")
    public ResponseEntity<Object> create(@Validated @RequestBody ItemCategory resources){
        return new ResponseEntity<>(itemCategoryService.create(resources),HttpStatus.CREATED);
    }

/*
*  Copyright 2019-2020 Zheng Jie
*
*  Licensed under the Apache License, Version 2.0 (the "License");
*  you may not use this file except in compliance with the License.
*  You may obtain a copy of the License at
*
*  http://www.apache.org/licenses/LICENSE-2.0
*
*  Unless required by applicable law or agreed to in writing, software
*  distributed under the License is distributed on an "AS IS" BASIS,
*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*  See the License for the specific language governing permissions and
*  limitations under the License.
*/
package me.zhengjie.modules.goods.domain;

import lombok.Data;
import cn.hutool.core.bean.BeanUtil;
import io.swagger.annotations.ApiModelProperty;
import cn.hutool.core.bean.copier.CopyOptions;
import javax.persistence.*;
import javax.validation.constraints.*;
import javax.persistence.Entity;
import javax.persistence.Table;
import org.hibernate.annotations.*;
import java.sql.Timestamp;
import java.io.Serializable;

/**
* @website https://el-admin.vip
* @description /
* @author lly
* @date 2020-07-01
**/
@Entity
@Data
@Table(name="item_category")
public class ItemCategory implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    @ApiModelProperty(value = "id")
    private Long id;

//    @Column(name = "parent_id")
//    @ApiModelProperty(value = "上级分类ID")
//    private Long parentId;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    @ApiModelProperty(value = "父类")
    private ItemCategory parent;

    @Column(name = "name",nullable = false)
    @NotBlank
    @ApiModelProperty(value = "分类名称")
    private String name;

    @Column(name = "update_time")
    @UpdateTimestamp
    @ApiModelProperty(value = "更新时间")
    private Timestamp updateTime;

    @Column(name = "create_date")
    @CreationTimestamp
    @ApiModelProperty(value = "创建时间")
    private Timestamp createDate;

    @Column(name = "available")
    @ApiModelProperty(value = "是否可用")
    private Integer available;

    public void copy(ItemCategory source){
        BeanUtil.copyProperties(source,this, CopyOptions.create().setIgnoreNullValue(true));
    }
}

https://cloud.tencent.com/developer/section/1489873  组件文档