react-router4 中设置NoMatch不起作用，如何解决？

Question

根据官网文档我这样设置NoMatch，但是当页面找不到没有跳转到NoMatch页面这是为什么？

<Router>
            <Switch>
                <Route exact path="/account/register" component={Register}/>
                <Route exact path="/account/login" component={Login}/>
                <Route exact path="/email/verify/:token" component={VerifyEmail}/>
                <Route path="/" component={Layout}/>
                <Route component={NoMatch}/>
            </Switch>
    </Router>

这是NoMatch组件：

import React from 'react'
import { withStyles } from 'material-ui/styles'

const styles = theme=>({

});

class NoMatch extends React.Component{
    constructor(props){
        super(props);
    }
    render(){
        return(
            <div>404 not found </div>
        )
    }
}

export default withStyles(styles)(NoMatch)

Answer 1

<Route path="/" component={Layout}/>

加上exact