报错提示如下：

Warning: setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op. Please check the code for the Timer component.

这里是我的代码（这里的props是接受另外一个组建传过来的数据）：

class Timer extends PureComponent {

    static propTypes = {
        aim: PropTypes.number

    };
    constructor(props) {
        super(props);
        this.state = {
            num: 0,
            days: 0
        }
    }
    tick() {
        if (this.props.aim) {
            const aimTime = new Date(this.props.aim);
            const currentTime = Date.parse(new Date());
            const leftTime = aimTime - currentTime;
            const day = aimTime.getDate();
            const hours = aimTime.getHours();
            this.setState({
                num: hours,
                days: day
            }, () => {
                if (currentTime === this.props.aim) {
                    clearInterval(this.interval);
                }
            });
        }else{
            this.setState({
                num: 0,
                days: 0
            })
        }
    }
    componentDidMount() {
        this.interval = setInterval(() => this.tick(), 1000);
    }
    componentWillMount(){
       clearInterval(this.interval);
        
    }
    render() {

        return (
            <span>还剩 {this.state.days} 天 {this.state.num} 小时</span>
        );
    }
}

这里附上stackflow里的答案，但是看了下不是很清楚。点击链接