react-router的withRouter方法是干嘛的，什么时候要用到？

Answer 1

首先withRouter可以用来给组件注入router相关的一些参数，比如：

```

import React from 'react'

import PropTypes from 'prop-types'

import { withRouter } from 'react-router'// A simple component that shows the pathname of the current location

class ShowTheLocation extends React.Component { 

static propTypes = { 

   match: PropTypes.object.isRequired, 

   location: PropTypes.object.isRequired, 

   history: PropTypes.object.isRequired
 }

  render() {

    const { match, location, history } = this.props

   return (
     <div>You are now at {location.pathname}</div>
   )
 }
}

// Create a new component that is "connected" (to borrow redux// terminology) to the router.

const ShowTheLocationWithRouter = withRouter(ShowTheLocation)

```

其次withRouter是专门用来处理数据更新问题的。在使用一些redux的的`connect()`或者mobx的`inject()`的组件中，如果依赖于路由的更新要重新渲染，会出现路由更新了但是组件没有重新渲染的情况。这是因为redux和mobx的这些连接方法会修改组件的`shouldComponentUpdate`。

座椅在使用withRouter解决更新问题的时候，一定要保证withRouter在最外层，比如`withRouter(connect(Component))`