问题描述
基本上,我有一个 react 组件,它的 render()
函数体如下:(这是我理想的一个,这意味着它目前不起作用)
render(){返回 (<div><元素 1/><元素2/>//注意:代码在这里不起作用if (this.props.hasImage) else
基本上,我有一个 react 组件,它的 render()
函数体如下:(这是我理想的一个,这意味着它目前不起作用)
render(){返回 (<div><元素 1/><元素2/>//注意:代码在这里不起作用if (this.props.hasImage) else
)}
不完全是这样,但有解决方法.React 的文档中有一节关于条件渲染,你应该看看.下面是使用内联 if-else 可以执行的操作的示例.
render() {const isLoggedIn = this.state.isLoggedIn;返回 (<div>{已登录?(<LogoutButton onClick={this.handleLogoutClick}/>) : (<LoginButton onClick={this.handleLoginClick}/>)}
);}
你也可以在render函数内部处理它,但是在返回jsx之前.
if (isLoggedIn) {button = <LogoutButton onClick={this.handleLogoutClick}/>;} 别的 {button = <LoginButton onClick={this.handleLoginClick}/>;}返回 (<div><问候 isLoggedIn={isLoggedIn}/>{按钮}
);
还值得一提的是 ZekeDroid 在评论中提出的内容.如果您只是检查条件并且不想呈现不符合要求的特定代码段,则可以使用 &&运算符
.
返回 (<div><h1>你好!</h1>{unreadMessages.length >0 &&<h2>您有 {unreadMessages.length} 条未读消息.}
);
Basically, I have a react component, its render()
function body is as below: (It is my ideal one, which means it currently does not work)
render(){
return (
<div>
<Element1/>
<Element2/>
// note: code does not work here
if (this.props.hasImage) <MyImage />
else <OtherElement/>
</div>
)
}
Not exactly like that, but there are workarounds. There's a section in React's docs about conditional rendering that you should take a look. Here's an example of what you could do using inline if-else.
render() {
const isLoggedIn = this.state.isLoggedIn;
return (
<div>
{isLoggedIn ? (
<LogoutButton onClick={this.handleLogoutClick} />
) : (
<LoginButton onClick={this.handleLoginClick} />
)}
</div>
);
}
You can also deal with it inside the render function, but before returning the jsx.
if (isLoggedIn) {
button = <LogoutButton onClick={this.handleLogoutClick} />;
} else {
button = <LoginButton onClick={this.handleLoginClick} />;
}
return (
<div>
<Greeting isLoggedIn={isLoggedIn} />
{button}
</div>
);
It's also worth mentioning what ZekeDroid brought up in the comments. If you're just checking for a condition and don't want to render a particular piece of code that doesn't comply, you can use the && operator
.
return (
<div>
<h1>Hello!</h1>
{unreadMessages.length > 0 &&
<h2>
You have {unreadMessages.length} unread messages.
</h2>
}
</div>
);
这篇关于是否可以在 React 渲染函数中使用 if...else... 语句?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!