Vue 级联下拉框的设计与实现
在前端开发中，级联选择框是经常用到的，这样不仅可以增加用户输入的友好性，还能减少前后端交互的数据量。本文以elementUI为例，使用其余UI组件大致思想也都相同。
1.数据库设计
所有的相关数据皆可存在一张表中，这样数据就可以不受层级的限制。
表结构可以参考如下建表SQL：
CREATE TABLE `supplies_type` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`category_type` varchar(64) NOT NULL COMMENT '类别种类：大类、中类、小类',
`big_category_name` varchar(64) NOT NULL COMMENT '大类名称',
`middle_category_name` varchar(64) DEFAULT NULL COMMENT '中类名称',
`small_category_name` varchar(64) DEFAULT NULL COMMENT '小类名称',
`parent_id` int(11) DEFAULT NULL,
`create_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
`create_user_name` varchar(64) DEFAULT NULL COMMENT '创建人用户名',
`update_time` timestamp NULL DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP,
`is_deleted` tinyint(1) DEFAULT '0' COMMENT '是否删除，1表示已删除',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4;
数据库截图如下图所示，注：本系统为了减少查询次数，故冗余了一些字段，读者可根据自己的需求调整。
核心设计在于parent_id，根据parent_id字段即可查询到子类，结果如下图所示：
2.前端页面
前端页面效果如下：
Html代码如下：
<div class="app-container">
<span style="margin-left:120px;margin-right: 20px;width: 150px;display: inline-block;">大类：</span>
<el-select v-model="big" placeholder="请选择" @change="getSuppliesType(big)" style="width: 19%;">
<el-option
v-for="item in bigTypes"
:key="item.bigCategoryName"
:label="item.bigCategoryName"
:value="item.id">
</el-option>
</el-select>
<span style="margin-left:120px;margin-right: 20px; width: 150px;display: inline-block;">中类：</span>
<el-select v-model="middle" placeholder="请选择" @change="getSuppliesType(middle)" style="width: 19%;">
<el-option
v-for="item in middleTypes"
:key="item.middleCategoryName"
:label="item.middleCategoryName"
:value="item.id">
</el-option>
</el-select>
<br>
<br>
<br>
<span style="margin-left:120px;margin-right: 20px;width: 150px; margin-top:20px; display: inline-block;">小类：</span>
<el-select v-model="small" placeholder="请选择" style="width: 19%;">
<el-option
v-for="item in smallTypes"
:key="item.smallCategoryName"
:label="item.smallCategoryName"
:value="item.id">
</el-option>
</el-select>
</div>
上面的item.smallCategoryName、item.smallCategoryName数据为后端从数据库中查询出来的数据（驼峰命名），后端只负责查询、并返回结果。
Vue中数据定义如下：
data() {
return {
big: '',
bigTypes: null,
middle: '',
middleTypes: null,
small: '',
smallTypes: null
}
},
在页面初始化时，自动获取大类列表：
created() {
this.getSuppliesType(0)
},
页面中的getSuppliesType方法如下：
getSuppliesType(id) {
this.listLoading = true
const queryData = {
parentId: id
}
//此处的调用后端接口按照自己的调用方式写即可
//此处的getSuppliersType是项目中自己封装的util中的方法
//如果请求方式是post，JSON.stringify(queryData)
//如果请求方式是get，queryData
getSuppliersType(JSON.stringify(queryData)).then(response => {
console.log(response)
console.log(response.data[0].categoryType)
//根据type自动向三个下拉框赋值
if (response.data[0].categoryType === 'BIG') {
this.bigTypes = response.data
} else if (response.data[0].categoryType === 'MIDDLE') {
this.middleTypes = response.data
} else {
this.smallTypes = response.data
}
this.listLoading = false
}).catch(function (error) {
console.log(error)
this.listLoading = false
})
},
3.一个完整的demo
下面这个页面为完成代码，其中的数据为部分数据，后台接口获取使用JS来完成。
<template>
<div class="app-container">
<span style="margin-left:120px;margin-right: 20px;width: 150px;display: inline-block;">大类：</span>
<el-select v-model="big" placeholder="请选择" @change="getSuppliesType(big)" style="width: 19%;">
<el-option
v-for="item in bigTypes"
:key="item.bigCategoryName"
:label="item.bigCategoryName"
:value="item.id">
</el-option>
</el-select>
<span style="margin-left:120px;margin-right: 20px; width: 150px;display: inline-block;">中类：</span>
<el-select v-model="middle" placeholder="请选择" @change="getSuppliesType(middle)" style="width: 19%;">
<el-option
v-for="item in middleTypes"
:key="item.middleCategoryName"
:label="item.middleCategoryName"
:value="item.id">
</el-option>
</el-select>
<br>
<br>
<br>
<span style="margin-left:120px;margin-right: 20px;width: 150px; margin-top:20px; display: inline-block;">小类：</span>
<el-select v-model="small" placeholder="请选择" style="width: 19%;">
<el-option
v-for="item in smallTypes"
:key="item.smallCategoryName"
:label="item.smallCategoryName"
:value="item.id">
</el-option>
</el-select>
<br>
<br>
<br>
<el-button type="primary" round style="margin-left:280px" @click.native.prevent="commit">添加</el-button>
<el-button type="primary" round style="margin-left:100px" @click.native.prevent="cancel">取消</el-button>
</div>
</template>
<script>
export default {
filters: {
parseTime(timestamp) {
return parseTime(timestamp, null)
}
},
data() {
return {
big: '',
bigTypes: null,
middle: '',
middleTypes: null,
small: '',
smallTypes: null,
dataList: [
{"id":1,"categoryType":"BIG","bigCategoryName":"1.现场管理与保障","middleCategoryName":null,"smallCategoryName":null,"parentId":0,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":"2021-07-04T13:34:31.000+0000","isDeleted":false},
{"id":27,"categoryType":"BIG","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":null,"smallCategoryName":null,"parentId":0,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":2,"categoryType":"MIDDLE","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":null,"parentId":1,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":10,"categoryType":"MIDDLE","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.2现场安全","smallCategoryName":null,"parentId":1,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":3,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.1气象监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":4,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.2地震监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":5,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.3地质灾害监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":6,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.4水文监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":7,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.5环境监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":8,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.6疫病监测","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":9,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.1现场监测","smallCategoryName":"1.1.7观察测量","parentId":2,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":11,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.2现场安全","smallCategoryName":"1.2.1现场照明","parentId":10,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":12,"categoryType":"SMALL","bigCategoryName":"1.现场管理与保障","middleCategoryName":"1.2现场安全","smallCategoryName":"1.2.2现场警戒","parentId":10,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":28,"categoryType":"MIDDLE","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":null,"parentId":27,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":34,"categoryType":"MIDDLE","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":null,"parentId":27,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":"2021-07-04T13:03:23.000+0000","isDeleted":false},
{"id":29,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.1卫生防疫","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":30,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.2消防防护","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":31,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.3化学与放射","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":32,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.4防高空坠落","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":33,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.1人员安全防护","smallCategoryName":"2.1.5通用防护","parentId":28,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":35,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":"2.2.1生命搜索","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":36,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":"2.2.2攀岩营救","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":37,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":"2.2.3破拆起重","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":38,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":"2.2.4水下营救","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false},
{"id":39,"categoryType":"SMALL","bigCategoryName":"2.生命救援与生活救助","middleCategoryName":"2.2生命搜救与营救","smallCategoryName":"2.2.5通用工具","parentId":34,"createTime":"2021-07-04T11:13:36.000+0000","createUserName":null,"updateTime":null,"isDeleted":false}
]
}
},
created() {
this.getSuppliesType(0)
},
methods: {
getSuppliesType(id) {
const queryData = {
parentId: id
}
//此处为js模拟，真实数据的获取还需要后台接口的支持
getSuppliersType(JSON.stringify(queryData)).then(response => {
console.log(response)
console.log(response.data[0].categoryType)
//存放此次查询结果
let tmpList = []
this.dataList.forEach((item, index) => {
if(item.parentId === id){
tmpList.push(item)
}
})
if (tmpList[0].categoryType === 'BIG') {
this.bigTypes = tmpList
} else if (response.data[0].categoryType === 'MIDDLE') {
this.middleTypes = tmpList
} else {
this.smallTypes = tmpList
}
}).catch(function (error) {
console.log(error)
})
},
commit() {
console.log("点击了提交按钮")
},
cancel() {
this.$router.go(-1)
}
}
}
</script>
又到了分隔线以下，本文到此就结束了，本文内容全部都是由博主自己进行整理并结合自身的理解进行总结
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