Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount method
这个警告的原因是当路由已经切换，过期的页面中还存在设置state的现象存在，造成内存泄漏，比较常见的就是存在定时器的情况，比如：
...
let this.timerStatus = setInterval (()=>{
if (this.state.status === '0') {
// 当满足某个状态就停止轮询
clearInterval(this.timerStatus );
} else {
this.setState({
status: this.state.status ++
});
}
},2000);
...
解决方法也简单：
...
componentWillUnmount () {
clearInterval(this.timerStatus );
}
...
