React Native之导出

1 React Native里面一般导出函数或者常量或者组件

如果是默认组件或者类(export default修饰)的话,在另外一个地方导入的时候不需要加上{},格式如下
导出

  export default class Student {}

导入

 import Student from "./file"

如果不是默认组件或类或则方法或则变量(没有用default修饰)的话,在另外一个地方导入的时候需要加上{},格式如下
导出:使用module.exports

  module.exports = {fun1, fun2, 常量}

导入

 import {xxx2, xxx2, ...} from "./file"

好处:在另外一个文件地方导入了,就可以使用导入的函数或者变量或者组件,非常方便,相当于java里面的import导入类文件一样.

还可以是用一个变量,然后变量里面放键值对数组,key是函数名字,value是函数实现

如下

let fun = {fun1 : (a, b) => {return a + b}, fun2 : (a, b) => {return a - b}} export default fun;

2 简单测试

Student.js文件如下

'use strict';import React from 'react'class Student {constructor(name: string) {this.name = name;}_getName = () => {console.log("_getName");return this.name;};
}export default Student

Fun.js文件如下

'use strict';import React from 'react'const sum = (a, b) => {return a + b;
}const sub = (a, b) => {return a - b;	
}const myName = 'chenyu';module.exports = {sum,sub,myName
}

Fun_second.js文件如下

'use strict';import React from 'react'//我们把所有的函数放在一个变量里面,这个变量里面放的都是键值对,
//然后key是函数名字,value是我们函数实现
let fun = {  //记得这是是let fun = { },不是let fun {} //相加函数sum : (a, b) => {return a + b;	},	//相减函数sub : (a, b) => {return a - b;	}
}export default fun;

App.js文件如下

import React from 'react';
import {View, Text} from 'react-native';
import {DeviceEventEmitter} from "react-native";import Student from "./Student"
import {sub, sum, myName} from "./Fun"
import fun from "./Fun_second"export default class App extends React.Component {constructor(props) {super(props); this.state = {name: '点击我',sumRes: 'sumRes',subRes: 'subRes',stuName: 'hello',sumRes_sec: 'sumRes_sec',subRes_: 'subRes_'};}render() {return (<View style={{flex: 1, alignItems: 'center', justifyContent: 'center'}}><TextonPress={() => this._press(5, 2)}>{this.state.name}</Text><Text>{this.state.sumRes}</Text><Text>{this.state.subRes}</Text><Text>{this.state.stuName}</Text><Text>{this.state.sumRes_sec}</Text><Text>{this.state.subRes_}</Text></View>);}_press = (a, b) => {this.setState({name: myName});let res = sum(a, b);console.log("res is:" + res);this.setState({sumRes : res});let res1 = sub(a, b);console.log("res1 is:" + res1);this.setState({subRes : res1});let student = new Student("chengongyu");let studentName = student._getName();this.setState({stuName : studentName});let sumSec = fun.sum(4, 9);this.setState({sumRes_sec : sumSec});let subSec = fun.sub(10, 2);this.setState({subRes_: subSec});}}