索引 Routes 和 索引 Links

索引 Routes

To illustrate the use case for IndexRoute, imagine the following route config without it:

<Router>
  <Route path="/" component={App}>
    <Route path="accounts" component={Accounts}/>
    <Route path="statements" component={Statements}/>
  </Route>
</Router>

When the user visits /, the App component is rendered, but none of the children are, so this.props.children inside of App will be undefined. To render some default UI you could easily do `{this.props.children ||

}`.

But now Home can't participate in routing, like the onEnter hooks, etc. You render in the same position as Accounts and Statements, so the router allows you to have Home be a first class route component with IndexRoute.

<Router>
  <Route path="/" component={App}>
    <IndexRoute component={Home}/>
    <Route path="accounts" component={Accounts}/>
    <Route path="statements" component={Statements}/>
  </Route>
</Router>

Now App can render {this.props.children} and we have a first-class route for Home that can participate in routing.

索引 Links

If you were to <Link to="/">Home</Link> in this app, it would always be active since every URL starts with /. This is a problem because we'd like to link to Home but only be active if Home is rendered.

To have a link to / that is only active when the Home route is rendered, use <IndexLink to="/">Home</IndexLink>.