使用memcpy连接两个字符串(Concatenate two strings using memcpy)

 所以你要做的是避免渲染任何东西，直到你的ajax请求返回你的结果。 
 
 如果状态是您想要的状态，您可以检查渲染方法。 如果不是，则返回null，或者加载器或其他标记。 当componentDidMount然后设置状态时，它将触发重新渲染，因为然后设置了userID，它将返回userShow组件 
 
 例： 
 
render(){
  if(this.state.userID === null){
     return null; //Or some other replacement component or markup
  }

  return (
    <div>
        <UserShow params={{id: userID}} />
    </div>
  );

}
 
 获取userShow组件中的数据可以这样完成： 
 
componentWillReceiveProps(nextProps){
    //fetch data her, you'll find your prop params in nextProps.params
}
 
 你也可以通过在render-method中踢数据获取来避免这样做。 

So what you want to do is to avoid rendering anything until your ajax-request returns your result.
 
You can do a check in the render method if the state is how you want it. If it's not, then return null, or a loader or some other markup. When the componentDidMount then sets the state, it will trigger a re-render, since the userID then is set, it will return the userShow component
 
Example:
 
render(){
  if(this.state.userID === null){
     return null; //Or some other replacement component or markup
  }

  return (
    <div>
        <UserShow params={{id: userID}} />
    </div>
  );

}
 
Fetching the data in the userShow component could be done like this:
 
componentWillReceiveProps(nextProps){
    //fetch data her, you'll find your prop params in nextProps.params
}
 
You can also avoid doing this here, by kicking the data-fetch in the render-method.