浅谈react-router@4.0 使用方法和源码分析

react-router-dom@4.3.0 || react-router@4.4.1

react-router 使用方法

配置 router.js

import React, { Component } from 'react';
import { Switch, Route } from 'react-router-dom';

const router = [{
  path: '/',
  exact: true,
  component:importPath({
   loader: () => import(/* webpackChunkName:"home" */ "pages/home/index.js"),
  }),
 },]
const Routers = () => (
 <main>
  <Switch>
   {
    router.map(({component,path,exact},index)=>{
     return <Route exact={exact} path={path} component={component} key={path} />
    })
   }
  </Switch>
 </main>
);

export default Routers;

入口 index.js

import {HashRouter} from 'react-router-dom';
import React from 'react';
import ReactDOM from 'react-dom';
import Routers from './router';

ReactDOM.render (
   <HashRouter>
    <Routers />
   </HashRouter>,
 document.getElementById ('App')
);

home.js

import { withRouter } from "react-router-dom";

@withRouter
class Home extends React.Component<PropsType, stateType> {
 constructor(props: PropsType) {
  super(props);
  this.state = {};
 }
 goPath=()=>{
   this.props.history.push('/home')
 }
 render() {
  return (
   <div onClick={this.goPath}>home</div>
  );
 }
export default Home;

react-router 源码解析

下面代码中会移除部分的类型检查和提醒代码，突出重点代码

第一步 Switch react-router

function _possibleConstructorReturn(self, call) {
 if (!self) {
  throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
 }
 if(call&&(typeof call === "object" || typeof call === "function") ){
  return call
 }else {
  return self
 }
}
var Switch = function (_React$Component) {
 function Switch() {
  //使用传递进来的组件覆盖本身
  return _possibleConstructorReturn(this, _React$Component.apply(this, arguments)); 
 }
 Switch.prototype.render = function render() {
  var route = this.context.router.route;
  var children = this.props.children;
  var location = this.props.location || route.location;
  var match = void 0,child = void 0;
  
  //检查element是否是react组件，初始match为null,
  React.Children.forEach(children, function (element) {
   //如果match符合，forEach不会进入该if
   if (match == null && React.isValidElement(element)) { 
    var _element$props = element.props,
      pathProp = _element$props.path,
      exact = _element$props.exact,
      strict = _element$props.strict,
      sensitive = _element$props.sensitive,
      from = _element$props.from;
    var path = pathProp || from;
    child = element; 
    //检查当前配置是否符合,
    match = matchPath(location.pathname, { path: path, exact: exact, strict: strict, sensitive: sensitive }, route.match); 
   }
  });
  //如果有匹配元素，则返回克隆child
  return match ? React.cloneElement(child, { location: location, computedMatch: match }) : null;
 };

 return Switch;
}(React.Component);

总结：switch根据location.pathname,path,exact,strict,sensitive获取元素并返回element

第二步 Route react-router

var Route = function (_React$Component) {
 function Route() {
  var _temp, _this, _ret;
  //获取参数
  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
   args[_key] = arguments[_key];
  }
  //修改this
  return _ret = (
   _temp = (_this = _possibleConstructorReturn(this, _React$Component.call.apply(_React$Component, [this].concat(args))), _this), 
   //检查当前元素是否符合match
   _this.state = {match: _this.computeMatch(_this.props,_this.context.router)},_temp),
    //这里是真正return
    _possibleConstructorReturn(_this, _ret); 
 }
 // 设置content
 Route.prototype.getChildContext = function getChildContext() {
  return {
   router: _extends({}, this.context.router, {
    route: {
     location: this.props.location || this.context.router.route.location,
     match: this.state.match
    }
   })
  };
 };
 // 根据参数检查当前元素是否符合匹配规则
 Route.prototype.computeMatch = function computeMatch(_ref, router) {
  var computedMatch = _ref.computedMatch,
    location = _ref.location,
    path = _ref.path,
    strict = _ref.strict,
    exact = _ref.exact,
    sensitive = _ref.sensitive;

  if (computedMatch) return computedMatch;

  var route = router.route;

  var pathname = (location || route.location).pathname;

  return matchPath(pathname, { path: path, strict: strict, exact: exact, sensitive: sensitive }, route.match);
 };
 // 设置match
 Route.prototype.componentWillReceiveProps = function componentWillReceiveProps(nextProps, nextContext) {
  this.setState({
   match: this.computeMatch(nextProps, nextContext.router)
  });
 };

 Route.prototype.render = function render() {
  var match = this.state.match;
  var _props = this.props,
    children = _props.children,
    component = _props.component,
    render = _props.render;
  var _context$router = this.context.router,
    history = _context$router.history,
    route = _context$router.route,
    staticContext = _context$router.staticContext;

  var location = this.props.location || route.location;
  var props = { match: match, location: location, history: history, staticContext: staticContext };
  //检查route 是否有component组
  if (component) return match ? React.createElement(component, props) : null; 
  // 检查是否包含render 组件
  if (render) return match ? render(props) : null;
  // withRouter 使用的方式
  if (typeof children === "function") return children(props);

  if (children && !isEmptyChildren(children)) return React.Children.only(children);

  return null;
 };

 return Route;
}(React.Component);

总结：route 渲染的方式: component render children,代码示例用的是component,route 是检查当前组件是否符合路由匹配规则并执行创建过程

第三步 HashRouter react-router-dom

import Router from './Router'
import {createHistory} from 'history'
var HashRouter = function (_React$Component) {
 function HashRouter() {
  var _temp, _this, _ret;
  //参数转换为数组
  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) { 
   args[_key] = arguments[_key];
  }
  return _ret = (
   _temp = (_this = _possibleConstructorReturn(this, _React$Component.call.apply(_React$Component, [this].concat(args))), _this),
    _this.history = createHistory(_this.props), _temp), //创建history
    _possibleConstructorReturn(_this, _ret); //真正返回的东西 返回this
 }
 HashRouter.prototype.render = function render() {
  // 返回一个Router,并且把history，children传递给Router
  return React.createElement(Router, { history: this.history, children: this.props.children });
 };
 return HashRouter;
}(React.Component);

总结 通过 history库里面 createHistory 创建路由系统

第四部 Router react-router

var Router = function (_React$Component) {
 function Router() {
  var _temp, _this, _ret;
  //获取参数，和其他组件一样
  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
   args[_key] = arguments[_key];
  }
  return _ret = (_temp = (_this = _possibleConstructorReturn(this, _React$Component.call.apply(_React$Component, [this].concat(args))), _this), _this.state = {
   match: _this.computeMatch(_this.props.history.location.pathname) //返回路由对象
  }, _temp), _possibleConstructorReturn(_this, _ret); //返回this
 }
 // 返回context
 Router.prototype.getChildContext = function getChildContext() {
  return {
   router: _extends({}, this.context.router, {
    history: this.props.history,
    route: {
     location: this.props.history.location,
     match: this.state.match
    }
   })
  };
 };
  
 Router.prototype.computeMatch = function computeMatch(pathname) {
  return {
   path: "/",
   url: "/",
   params: {},
   isExact: pathname === "/"
  };
 };

 Router.prototype.componentWillMount = function componentWillMount() {
  var _this2 = this;

  var _props = this.props,
    children = _props.children,
    history = _props.history;

  // 启动监听 当hash 改变是做一次检查，并返回unlisten 取消事件
  this.unlisten = history.listen(function () {
   _this2.setState({
    match: _this2.computeMatch(history.location.pathname)
   });
  });
 };
 //销毁前取消监听
 Router.prototype.componentWillUnmount = function componentWillUnmount() {
  this.unlisten();
 };
 // children是HashRouter 传递进来的
 Router.prototype.render = function render() {
  var children = this.props.children;
  return children ? React.Children.only(children) : null;
 };

 return Router;
}(React.Component);

总结 history是一个JavaScript库，可让您在JavaScript运行的任何地方轻松管理会话历史记录。history抽象出各种环境中的差异，并提供最小的API，使您可以管理历史堆栈，导航，确认导航以及在会话之间保持状态。

第五部 withRouter <react-router>

var withRouter = function withRouter(Component) {
 var C = function C(props) {
  //获取props
  var wrappedComponentRef = props.wrappedComponentRef,
    remainingProps = _objectWithoutProperties(props, ["wrappedComponentRef"]);
  // Route 组件 children方式
  return React.createElement(Route, {
   children: function children(routeComponentProps) {
    // 这里使用的是route 组件 children(props)
    //routeComponentProps 实际等于 { match: match, location: location, history: history, staticContext: staticContext };
    return React.createElement(Component, _extends({}, remainingProps, routeComponentProps, {
     ref: wrappedComponentRef
    }));
   }
  });
 };

 C.displayName = "withRouter(" + (Component.displayName || Component.name) + ")";
 C.WrappedComponent = Component;
 // 该类似于object.assign(C,Component),得到的结果是C
 return hoistStatics(C, Component);
};

到这里真个流程基本结束了，这只是react-router的一种使用方式的解析,本文的目的是理解react-router的运行机制,如果有什么错误还望指出,谢谢