Element-UI远程搜索功能详解

官方代码：

<template>
    <div>
        <el-autocomplete
            v-model="state"
            :fetch-suggestions="querySearchAsync"
            placeholder="请输入内容"
            @select="handleSelect"
            ></el-autocomplete>
    </div>
</template>
<script>
  export default {
    data() {
      return {
        restaurants: [],
        state: '',
        timeout:  null
      };
    },
    methods: {
      loadAll() {
        return [
          { "value": "三全鲜食（北新泾店）", "address": "长宁区新渔路144号" },
          { "value": "Hot honey 首尔炸鸡（仙霞路）", "address": "上海市长宁区淞虹路661号" },
          { "value": "新旺角茶餐厅", "address": "上海市普陀区真北路988号创邑金沙谷6号楼113" },
          { "value": "泷千家(天山西路店)", "address": "天山西路438号" },
          { "value": "胖仙女纸杯蛋糕（上海凌空店）", "address": "上海市长宁区金钟路968号1幢18号楼一层商铺18-101" },
          { "value": "贡茶", "address": "上海市长宁区金钟路633号" },
          { "value": "豪大大香鸡排超级奶爸", "address": "上海市嘉定区曹安公路曹安路1685号" },
          { "value": "茶芝兰（奶茶，手抓饼）", "address": "上海市普陀区同普路1435号" },
          { "value": "十二泷町", "address": "上海市北翟路1444弄81号B幢-107" },
          { "value": "星移浓缩咖啡", "address": "上海市嘉定区新郁路817号" },
          { "value": "阿姨奶茶/豪大大", "address": "嘉定区曹安路1611号" },
          { "value": "新麦甜四季甜品炸鸡", "address": "嘉定区曹安公路2383弄55号" },
          { "value": "Monica摩托主题咖啡店", "address": "嘉定区江桥镇曹安公路2409号1F，2383弄62号1F" },
          { "value": "浮生若茶（凌空soho店）", "address": "上海长宁区金钟路968号9号楼地下一层" },
          { "value": "NONO JUICE  鲜榨果汁", "address": "上海市长宁区天山西路119号" },
          { "value": "CoCo都可(北新泾店）", "address": "上海市长宁区仙霞西路" },
          { "value": "快乐柠檬（神州智慧店）", "address": "上海市长宁区天山西路567号1层R117号店铺" },
          { "value": "Merci Paul cafe", "address": "上海市普陀区光复西路丹巴路28弄6号楼819" },
          { "value": "猫山王（西郊百联店）", "address": "上海市长宁区仙霞西路88号第一层G05-F01-1-306" },
          { "value": "枪会山", "address": "上海市普陀区棕榈路" },
          { "value": "纵食", "address": "元丰天山花园(东门) 双流路267号" },
          { "value": "钱记", "address": "上海市长宁区天山西路" },
          { "value": "壹杯加", "address": "上海市长宁区通协路" },
          { "value": "唦哇嘀咖", "address": "上海市长宁区新泾镇金钟路999号2幢（B幢）第01层第1-02A单元" },
          { "value": "爱茜茜里(西郊百联)", "address": "长宁区仙霞西路88号1305室" },
          { "value": "爱茜茜里(近铁广场)", "address": "上海市普陀区真北路818号近铁城市广场北区地下二楼N-B2-O2-C商铺" },
          { "value": "鲜果榨汁（金沙江路和美广店）", "address": "普陀区金沙江路2239号金沙和美广场B1-10-6" },
          { "value": "开心丽果（缤谷店）", "address": "上海市长宁区威宁路天山路341号" },
          { "value": "超级鸡车（丰庄路店）", "address": "上海市嘉定区丰庄路240号" },
          { "value": "妙生活果园（北新泾店）", "address": "长宁区新渔路144号" },
          { "value": "香宜度麻辣香锅", "address": "长宁区淞虹路148号" },
          { "value": "凡仔汉堡（老真北路店）", "address": "上海市普陀区老真北路160号" },
          { "value": "港式小铺", "address": "上海市长宁区金钟路968号15楼15-105室" },
          { "value": "蜀香源麻辣香锅（剑河路店）", "address": "剑河路443-1" },
          { "value": "北京饺子馆", "address": "长宁区北新泾街道天山西路490-1号" },
          { "value": "饭典*新简餐（凌空SOHO店）", "address": "上海市长宁区金钟路968号9号楼地下一层9-83室" },
          { "value": "焦耳·川式快餐（金钟路店）", "address": "上海市金钟路633号地下一层甲部" },
          { "value": "动力鸡车", "address": "长宁区仙霞西路299弄3号101B" },
          { "value": "浏阳蒸菜", "address": "天山西路430号" },
          { "value": "四海游龙（天山西路店）", "address": "上海市长宁区天山西路" },
          { "value": "樱花食堂（凌空店）", "address": "上海市长宁区金钟路968号15楼15-105室" },
          { "value": "壹分米客家传统调制米粉(天山店)", "address": "天山西路428号" },
          { "value": "福荣祥烧腊（平溪路店）", "address": "上海市长宁区协和路福泉路255弄57-73号" },
          { "value": "速记黄焖鸡米饭", "address": "上海市长宁区北新泾街道金钟路180号1层01号摊位" },
          { "value": "红辣椒麻辣烫", "address": "上海市长宁区天山西路492号" },
          { "value": "(小杨生煎)西郊百联餐厅", "address": "长宁区仙霞西路88号百联2楼" },
          { "value": "阳阳麻辣烫", "address": "天山西路389号" },
          { "value": "南拳妈妈龙虾盖浇饭", "address": "普陀区金沙江路1699号鑫乐惠美食广场A13" }
        ];
      },
      querySearchAsync(queryString, cb) {
        var restaurants = this.restaurants;
        var results = queryString ? restaurants.filter(this.createStateFilter(queryString)) : restaurants;
        clearTimeout(this.timeout);
        this.timeout = setTimeout(() => {
          cb(results);
        }, 3000 * Math.random());
      },
      // 过滤出state.value中包含queryString的记录
      createStateFilter(queryString) {
        return (state) => {
          return (state.value.toLowerCase().indexOf(queryString.toLowerCase()) === 0);
        };
      },
      handleSelect(item) {
        // console.log(item);
      }
    },
    mounted() {
      this.restaurants = this.loadAll();
    }
  };
</script>

页面渲染完成后，就模拟从后台获取的数据赋值给this.restaurants。当你点击输入框，此时还没输入数据，queryString为空字符串，results为restaurants，当你输入字符，如“港式”，则queryString就是“港式”，此时queryString不为空，此时results为{ "value": "港式小铺", "address": "上海市长宁区金钟路968号15楼15-105室" }

使用el-autocomplete标签，fetch-suggestions属性：返回输入建议的方法，仅当你的输入建议数据 resolve 时，通过调用 callback(data:[]) 来返回它。

callback 是一种特殊的函数，这个函数被作为参数传给另一个函数去调用。这样的函数就是回调函数。callback 就是传给另一个函数调用的函数

实现的机制
[1]定义一个回调函数；
[2]提供函数实现的一方在初始化的时候，将回调函数的函数指针注册给调用者；
[3]当特定的事件或条件发生的时候，调用者使用函数指针调用回调函数对事件进行处理。

自己的理解：

[1]定义一个回调函数 (cb)；
[2]提供函数实现的一方在初始化的时候，将回调函数的函数指针注册给调用者(fetch-suggestions)；

[3]当特定的事件或条件发生的时候，调用者(fetch-suggestions)使用函数指针调用回调函数 (cb)对事件进行处理。

实际工程中应用：

<el-form-item label="药品通用名" prop="commonName">
  <el-autocomplete v-model="ruleForm.commonName" :fetch-suggestions="querySearch" placeholder="请输入药品通用名"></el-autocomplete>
</el-form-item>

//查询搜索处理
querySearch(name, callback) {
  if (name != null && name.length > 0) {
//获取搜索数据
    medicineListApi.getListByLike({ name }).then(res => {
      const list = []
      //封装要显示的数据
      for (let v of res) {
        list.push({ value: v.drugname })
      }
      // 调用 callback 返回建议列表的数据,是一个数组类型
      callback(list)
    }, err => {
      console.log(err)
    })
  }
},

在medicineList.js中的代码

//根据名字进行模糊查询，实现搜索提示
getListByLike(params) {
  return request.get(baseUrl + "/listByName", { params });
},

后台代码：

controller

@GetMapping("/listByName")
public List<DrugData> getList(@RequestParam  String name) {
    QueryWrapper<DrugData> wrapper = new QueryWrapper<>();
    wrapper.like("drugname",name);
    return medicineListService.list(wrapper);
}

service接口：

public interface MedicineListService extends IService<DrugData> {
}

service实现类

@Service
public class MedicineListServiceImpl extends ServiceImpl<MedicineListMapper,DrugData> implements MedicineListService {
    @Resource
    private MedicineListMapper medicineListMapper;
}

Dao接口

public interface MedicineListMapper extends BaseMapper<DrugData> {
}