uni-form的下拉框是怎么做的？

<template>
  <view class="container">
    <uni-card :is-shadow="false" is-full>
      <text class="uni-h6">uni-forms 组件一般由输入框、选择器、单选框、多选框等控件组成，用以收集、校验、提交数据。</text>
    </uni-card>
    <uni-section title="基本用法" type="line">
      <view class="example">
        <!-- 基础用法，不包含校验规则 -->
        <uni-forms ref="baseForm" :model="baseFormData" labelWidth="80px">
          <uni-forms-item label="姓名" required>
            <uni-easyinput v-model="baseFormData.name" placeholder="请输入姓名" />
          </uni-forms-item>
          <uni-forms-item label="年龄" required>
            <uni-easyinput v-model="baseFormData.age" placeholder="请输入年龄" />
          </uni-forms-item>
          <uni-forms-item label="性别" required>
            <uni-data-checkbox v-model="baseFormData.sex" :localdata="sexs" />
          </uni-forms-item>
          <uni-forms-item label="兴趣爱好" required>
            <uni-data-checkbox v-model="baseFormData.hobby" multiple :localdata="hobbys" />
          </uni-forms-item>
          <uni-forms-item label="自我介绍">
            <uni-easyinput
              type="textarea"
              v-model="baseFormData.introduction"
              placeholder="请输入自我介绍"
            />
          </uni-forms-item>
          <uni-forms-item label="日期时间">
            <uni-datetime-picker
              type="datetime"
              return-type="timestamp"
              v-model="baseFormData.datetimesingle"
            />
          </uni-forms-item>
          <uni-forms-item label="选择城市">
            <uni-data-picker v-model="baseFormData.city" :localdata="cityData" popup-title="选择城市"></uni-data-picker>
          </uni-forms-item>
          <uni-forms-item label="选择技能">
            <uni-data-select v-model="baseFormData.skills" :localdata="typeArr"></uni-data-select>
          </uni-forms-item>
        </uni-forms>
      </view>
    </uni-section>

    <uni-section title="对齐方式" type="line">
      <view class="example">
        <view class="segmented-control">
          <uni-segmented-control
            :current="current"
            :values="items"
            @clickItem="onClickItem"
            styleType="button"
          ></uni-segmented-control>
        </view>
        <!-- 展示不同的排列方式 -->
        <uni-forms ref="baseForm" :modelValue="alignmentFormData" :label-position="alignment">
          <uni-forms-item label="姓名" required>
            <uni-easyinput v-model="baseFormData.name" placeholder="请输入姓名" />
          </uni-forms-item>
          <uni-forms-item label="年龄" required>
            <uni-easyinput v-model="baseFormData.age" placeholder="请输入年龄" />
          </uni-forms-item>
        </uni-forms>
      </view>
    </uni-section>

    <uni-section title="表单校验" type="line">
      <view class="example">
        <!-- 基础表单校验 -->
        <uni-forms ref="valiForm" :rules="rules" :model="valiFormData" labelWidth="80px">
          <uni-forms-item label="姓名" required name="name">
            <uni-easyinput v-model="valiFormData.name" placeholder="请输入姓名" />
          </uni-forms-item>
          <uni-forms-item label="年龄" required name="age">
            <uni-easyinput v-model="valiFormData.age" placeholder="请输入年龄" />
          </uni-forms-item>
          <uni-forms-item label="自我介绍">
            <uni-easyinput
              type="textarea"
              v-model="valiFormData.introduction"
              placeholder="请输入自我介绍"
            />
          </uni-forms-item>
        </uni-forms>
        <button type="primary" @click="submit('valiForm')">提交</button>
      </view>
    </uni-section>

    <uni-section title="自定义校验规则" type="line">
      <view class="example">
        <!-- 自定义表单校验 -->
        <uni-forms
          ref="customForm"
          :rules="customRules"
          labelWidth="80px"
          :modelValue="customFormData"
        >
          <uni-forms-item label="姓名" required name="name">
            <uni-easyinput v-model="customFormData.name" placeholder="请输入姓名" />
          </uni-forms-item>
          <uni-forms-item label="年龄" required name="age">
            <uni-easyinput v-model="customFormData.age" placeholder="请输入年龄" />
          </uni-forms-item>
          <uni-forms-item label="兴趣爱好" required name="hobby">
            <uni-data-checkbox v-model="customFormData.hobby" multiple :localdata="hobbys" />
          </uni-forms-item>
        </uni-forms>
        <button type="primary" @click="submit('customForm')">提交</button>
      </view>
    </uni-section>

    <uni-section title="动态表单" type="line">
      <view class="example">
        <!-- 动态表单校验 -->
        <uni-forms
          ref="dynamicForm"
          :rules="dynamicRules"
          :model="dynamicFormData"
          labelWidth="80px"
        >
          <uni-forms-item label="邮箱" required name="email">
            <uni-easyinput v-model="dynamicFormData.email" placeholder="请输入姓名" />
          </uni-forms-item>
          <uni-forms-item
            v-for="(item,index) in dynamicFormData.domains"
            :key="item.id"
            :label="item.label+' '+index"
            required
            :rules="item.rules"
            :name="['domains',index,'value']"
          >
            <view class="form-item">
              <uni-easyinput v-model="dynamicFormData.domains[index].value" placeholder="请输入域名" />
              <button class="button" size="mini" type="default" @click="del(item.id)">删除</button>
            </view>
          </uni-forms-item>
        </uni-forms>
        <view class="button-group">
          <button type="primary" size="mini" @click="add">新增域名</button>
          <button type="primary" size="mini" @click="submit('dynamicForm')">提交</button>
        </view>
      </view>
    </uni-section>
  </view>
</template>

<script>
export default {
  data() {
    return {
      // 基础表单数据
      baseFormData: {
        name: '',
        age: '',
        introduction: '',
        sex: 2,
        hobby: [5],
        datetimesingle: 1627529992399,
        city: '',
        skills: 0,
      },
      // 城市数据
      cityData: [
        {
          text: '北京',
          value: '10001',
        },
        {
          text: '上海',
          value: '10002',
        },
        {
          text: '深圳',
          value: '10004',
        },
      ],
      typeArr: [
        {
          value: 0,
          text: '电表',
        },
        {
          value: 1,
          text: '水表',
        },
      ],
      // 表单数据
      alignmentFormData: {
        name: '',
        age: '',
      },
      // 单选数据源
      sexs: [
        {
          text: '男',
          value: 0,
        },
        {
          text: '女',
          value: 1,
        },
        {
          text: '保密',
          value: 2,
        },
      ],
      // 多选数据源
      hobbys: [
        {
          text: '跑步',
          value: 0,
        },
        {
          text: '游泳',
          value: 1,
        },
        {
          text: '绘画',
          value: 2,
        },
        {
          text: '足球',
          value: 3,
        },
        {
          text: '篮球',
          value: 4,
        },
        {
          text: '其他',
          value: 5,
        },
      ],
      // 分段器数据
      current: 0,
      items: ['左对齐', '顶部对齐'],
      // 校验表单数据
      valiFormData: {
        name: '',
        age: '',
        introduction: '',
      },
      // 校验规则
      rules: {
        name: {
          rules: [
            {
              required: true,
              errorMessage: '姓名不能为空',
            },
          ],
        },
        age: {
          rules: [
            {
              required: true,
              errorMessage: '年龄不能为空',
            },
            {
              format: 'number',
              errorMessage: '年龄只能输入数字',
            },
          ],
        },
      },
      // 自定义表单数据
      customFormData: {
        name: '',
        age: '',
        hobby: [],
      },
      // 自定义表单校验规则
      customRules: {
        name: {
          rules: [
            {
              required: true,
              errorMessage: '姓名不能为空',
            },
          ],
        },
        age: {
          rules: [
            {
              required: true,
              errorMessage: '年龄不能为空',
            },
          ],
        },
        hobby: {
          rules: [
            {
              format: 'array',
            },
            {
              validateFunction: function (rule, value, data, callback) {
                if (value.length < 2) {
                  callback('请至少勾选两个兴趣爱好')
                }
                return true
              },
            },
          ],
        },
      },
      dynamicFormData: {
        email: '',
        domains: [],
      },
      dynamicLists: [],
      dynamicRules: {
        email: {
          rules: [
            {
              required: true,
              errorMessage: '域名不能为空',
            },
            {
              format: 'email',
              errorMessage: '域名格式错误',
            },
          ],
        },
      },
    }
  },
  computed: {
    // 处理表单排列切换
    alignment() {
      if (this.current === 0) return 'left'
      if (this.current === 1) return 'top'
      return 'left'
    },
  },
  onLoad() {},
  onReady() {
    // 设置自定义表单校验规则，必须在节点渲染完毕后执行
    this.$refs.customForm.setRules(this.customRules)
  },
  methods: {
    onClickItem(e) {
      console.log(e)
      this.current = e.currentIndex
    },
    add() {
      this.dynamicFormData.domains.push({
        label: '域名',
        value: '',
        rules: [
          {
            required: true,
            errorMessage: '域名项必填',
          },
        ],
        id: Date.now(),
      })
    },
    del(id) {
      let index = this.dynamicLists.findIndex((v) => v.id === id)
      this.dynamicLists.splice(index, 1)
    },
    submit(ref) {
      console.log(this.baseFormData)
      this.$refs[ref]
        .validate()
        .then((res) => {
          console.log('success', res)
          uni.showToast({
            title: `校验通过`,
          })
        })
        .catch((err) => {
          console.log('err', err)
        })
    },
  },
}
</script>

<style lang="scss">
.example {
  padding: 15px;
  background-color: #fff;
}

.segmented-control {
  margin-bottom: 15px;
}

.button-group {
  margin-top: 15px;
  display: flex;
  justify-content: space-around;
}

.form-item {
  display: flex;
  align-items: center;
  flex: 1;
}

.button {
  display: flex;
  align-items: center;
  height: 35px;
  line-height: 35px;
  margin-left: 10px;
}
</style>