正常在jsx中写法如下：

class Header extends Component<any>{

    myInputRef = React.createRef();
    render(){
        return(
            <div>
                <input type="text" ref={this.myInputRef}/>
            </div>
        )
    }
}

但是在tsx中由于类型检查，会编译报错：

Type 'RefObject<unknown>' is not assignable to type 'string | ((instance: HTMLInputElement | null) => void) | RefObject<HTMLInputElement> | null | undefined'.
Type 'RefObject<unknown>' is not assignable to type 'RefObject<HTMLInputElement>'.
Type 'unknown' is not assignable to type 'HTMLInputElement'.ts(2322)

看错误信息，需要添加类型，改为：

myInputRef = React.createRef<HTMLInputElement>();

参考：

https://medium.com/@martin_hotell/react-refs-with-typescript-a32d56c4d315