我有一个React组件，在组件的渲染方法中，我有这样的东西:
render() {
return (
<div>
<div>
// removed for brevity
</div>
{ switch(...) {} }
<div>
// removed for brevity
</div>
</div>
);
}
Now the point is that I have two div elements, one at the top and one at the bottom, that are fixed. In the middle I want to have a switch statement, and according to a value in my state I want to render a different component. So basically, I want the two div elements to be fixed always, and just in the middle to render a different component each time. I'm using this to implement a multi-step payment procedure). Though, as is the code currently it doesn't work, as it gives me an error saying that switch is unexpected. Any ideas how to achieve what I want?
你不能在渲染中有开关。放置访问一个元素的对象文字的伪切换方法并不理想，因为它会导致所有视图都要处理，并且可能导致在该状态下不存在的道具的依赖错误。
这里有一个很好的干净的方法来做到这一点，不需要每个视图提前渲染:
render () {
const viewState = this.getViewState();
return (
<div>
{viewState === ViewState.NO_RESULTS && this.renderNoResults()}
{viewState === ViewState.LIST_RESULTS && this.renderResults()}
{viewState === ViewState.SUCCESS_DONE && this.renderCompleted()}
</div>
)
如果视图状态的条件不只基于一个简单的属性——比如每行有多个条件，那么枚举和getViewState函数封装条件是分离条件逻辑和清理呈现的好方法。
我不太喜欢当前的任何答案，因为它们要么太啰嗦，要么需要您在代码中跳跃才能理解发生了什么。
我更喜欢用一个更以react组件为中心的方式来做这件事，通过创建一个<Switch/>。这个组件的任务是获取一个道具，并且只呈现子道具与该道具匹配的子元素。所以在下面的例子中，我在开关上创建了一个测试道具，并将其与子节点上的值道具进行比较，只渲染匹配的值道具。
例子:
const Switch = props => {
const { test, children } = props
// filter out only children with a matching prop
return children.find(child => {
return child.props.value === test
})
}
const Sample = props => {
const someTest = true
return (
<Switch test={someTest}>
<div value={false}>Will display if someTest is false</div>
<div value={true}>Will display if someTest is true</div>
</Switch>
)
}
ReactDOM.render(
<Sample/>,
document.getElementById("react")
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="react"></div>
您可以根据自己的需要进行简单或复杂的切换。不要忘记对子节点及其值道具执行更健壮的检查。
import React from 'react';
import ListView from './ListView';
import TableView from './TableView';
function DataView({
currView,
data,
onSelect,
onChangeStatus,
viewTodo,
editTodo,
deleteTodo,
}) {
return (
<div>
{(function () {
switch (currView) {
case 'table':
return (
<TableView
todos={data}
onSelect={onSelect}
onChangeStatus={onChangeStatus}
viewTodo={viewTodo}
editTodo={editTodo}
deleteTodo={deleteTodo}
/>
);
case 'list':
return (
<ListView
todos={data}
onSelect={onSelect}
onChangeStatus={onChangeStatus}
viewTodo={viewTodo}
editTodo={editTodo}
deleteTodo={deleteTodo}
/>
);
default:
break;
}
})()}
</div>
);
}
export default DataView;
我正在使用这个帮助器，它允许我在JSX中有开关语句
// in helpers folder
const switchTrue = (object) => {
const { default: defaultValue, ...rest } = object;
const obj = { default: defaultValue, ...rest };
const result = Object.keys(obj).reduce((acc, cur) => {
return {
...acc,
[cur === 'default' ? 'true' : cur]: obj[cur],
};
}, {});
return result['true'];
};
const Sample = () => {
const isDataLoading = false;
return (
<div>
{
switchTrue({
[`${isDataLoading}`]: <div>Loading</div>,
[`${!isDataLoading}`]: <div>Data Ready</div>,
default: <div>Default</div>,
})
}
</div>
)
}
ReactDOM.render(
<Sample/>,
document.getElementById("react")
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="react"></div>
