之前一直用的antd的Select组件，但在有些端并不适用，而原生的select样式修改不灵活，遂产生自己写一个组件的想法。观察select组件：

<select onChange={(value) => {this.value=value}}
 <option value='1'>man</option>
 <option value='0'>woman</option>
</select>

可以看出数据都是在option中，有值value和显示出来的数据一一对应。如果我们写一个select组件，那么应该有onChange方法，应该要访问到子元素，而且div是没有value这个属性的，所以option应该也是一个组件，有value属性。下面是我写的组件的用法：

import {MobileSelect, MobileOption} from '../../components/MobileSelect';

 <MobileSelect
 disabled={isDisabled}
 value={data.clarity || ringResponse.clarity || 'Flawless'}
 style={{ width: '132px' }}
 onChange={(v) => this.changeDataValue('clarity', v)}
 >
 {
 (clarity || []).map((item, i) => {
 return (
 <MobileOption key={i + ''} value={item.code}>{item.title}</MobileOption>
 );
 })
 }
 </MobileSelect>

可以看出其和一般的select组件用法差不多。效果如下：

下面是组件

import {observable} from 'mobx';
import {observer} from 'mobx-react';
import React from 'react';
import {Icon} from 'antd';
import './index.less';

interface IProps {
 disabled?: boolean;
 onChange?: (value) => void;
 value?: string | number;
 style?: React.CSSProperties;
 className?: string;
}
@observer
export class MobileSelect extends React.Component<IProps> {
 @observable showOption = false; // 是否弹出下拉框
 @observable value: any = ''; // 当前选中的value值
 @observable text: any = ''; // 选中的value值对应的文本
 @observable cell: any; // 组件的dom节点
 componentDidMount(): void {
 // 获取选择框的ref，当在组件外点击时的时候收起下拉框
 document.addEventListener('click', (e) => {
 if (this.cell && this.cell !== e.target && !this.cell.contains(e.target)) {
 this.showOption = false;
 }
 }, true);
 }
 componentWillReceiveProps(nextProps: Readonly<IProps>, nextContext: any): void {
 // 根据传入的value值，遍历children，找到对应值的展示文本
 if (nextProps.value !== this.props.value || nextProps.children !== this.props.children) {
 React.Children.map(this.props.children, (child, index) => {
 if (nextProps.value === child.props.value) {
 this.text = child.props.children;
 }
 });
 }
 }
 render(): React.ReactNode {
 const {children, value} = this.props;
 console.log(value);
 return (
 <div
 className={'Mobile-Select ' + this.props.className}
 style={this.props.style}
 ref={(node) => this.cell = node}
 >
 <div
 className={'select-wrap'}
 onClick={() => {
 // 禁用不能弹出下拉框
 if (!this.props.disabled) {
 this.showOption = !this.showOption;
 }
 }}
 >
 <Icon type='down' style={this.showOption ? {transform: 'rotate(180deg)'} : {transform: 'rotate(0deg)'}} className={'select-icon'}/>
 {this.text}
 </div>
 <div className={'option-wrap'} style={this.showOption ? {position: 'absolute'} : {display: 'none'}}>
 {
 React.Children.map(children, (child, index) => {
 // 设置选中option和未选中option的样式
 let optionClassName = '';
 if (this.props.value === child.props.value) {
 optionClassName = child.props.className ? child.props.className + ' option-item selected' : 'option-item selected';
 } else {
 optionClassName = child.props.className + ' option-item';
 }
 return (
 <div
 onClick={() => { // 为了在父组件给子组件添加onClick事件，包裹了一层div
 // 有无onChange事件都能改变值
 if (this.props.value && this.props.onChange) {
 this.props.onChange(child.props.value);
 } else {
 this.text = child.props.children;
 this.value = child.props.value;
 }
 console.log(this.value);
 this.showOption = !this.showOption;
 }}
 style={this.props.style}
 className={optionClassName}
 >{child}</div>
 );
 })
 }
 </div>
 </div>
 );
 }
}
interface OptionProps {
 value?: string | number;
 className?: string;
 style?: React.CSSProperties;
}
export class MobileOption extends React.Component<OptionProps> {
 render(): React.ReactNode {
 const {children} = this.props;
 return (
 <div style={this.props.style}>
 {children}
 </div>
 );
 }
}

下面是组件的样式

.Mobile-Select {
 display: inline-block;
 min-width: 100px;
 margin: 0 6px;
 .select-wrap {
 border: 1px solid #e0c0a2;
 border-radius: 4px;
 padding: 5px 11px;
 display: flex;
 flex-direction: row-reverse;
 justify-content: space-between;
 align-items: center;
 .select-icon {
 transition: .3s;
 float: right;
 }
 }
 .option-wrap {
 box-shadow: 0 0 5px #333;
 z-index: 1000;
 border-radius: 5px;
 .option-item {
 background-color: #fff;
 padding: 2px 11px;
 min-width: 100px;
 &.selected {
 background-color: #fbe6d0;
 }
 }
 }
}

总的来说只实现了select的基本功能。有改进的地方请指点一二。

PS：React Select默认值选中问题

import React from "react";
import { render } from "react-dom";

class App extends React.Component {
 constructor(props) {
 super(props);
 this.state = {
 projects: [],
 value: ""
 };
 }
 componentDidMount() {
 // 模拟ajax调用，成功之后把需要改变的默认值赋值给this.state.value
 setTimeout(() => {
 this.setState({
 projects: [
 { id: 1, name: "花生" },
 { id: 2, name: "苹果" },
 { id: 3, name: "杨桃" }
 ],
 value: 1
 });
 }, 3000);
 }
 handleClick() {
 this.setState({
 projects: [
 { id: 4, name: "水果" },
 { id: 5, name: "西瓜" },
 { id: 6, name: "哈哈哈" }
 ],
 value: 4
 });
 }
 handleChange = e => {
 this.setState({
 value: e.target.value
 });
 };
 render() {
 let projects = this.state.projects;
 return (
 <div>
 <button onClick={this.handleClick.bind(this)}>异步拉取数据</button>
 {/* 这里不用再去判断project的长度是否大于0，在ajax里面做判断就行，如果小于零或者不存在它就是默认值 */}
 <select
 defaultValue=""
 value={this.state.value}
 onChange={this.handleChange}
 >
 {projects.length > 0 &&
 projects.map((item, i) => {
 return (
 <option key={i} value={item.id}>
 {item.name}
 </option>
 );
 })}
 </select>
 </div>
 );
 }
}

render(<App />, document.getElementById("root"));