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?


当前回答

这个助手应该可以做到这一点。 使用示例:

{componentSwitch(3, (switcher => switcher
    .case(1, () =>
        <p>It is one</p>
    )
    .case(2, () =>
        <p>It is two</p>
    )
    .default(() =>
        <p>It is something different</p>
    )
))}

助手:

interface SwitchCases<T> {
    case: (value: T, result: () => React.ReactNode) => SwitchCases<T>;
    default: (result: () => React.ReactNode) => SwitchCases<T>;
}

export function componentSwitch<T>(value: T, cases: (cases: SwitchCases<T>) => void) {

    var possibleCases: { value: T, result: () => React.ReactNode }[] = [];
    var defaultResult: (() => React.ReactNode) | null = null;

    var getSwitchCases: () => SwitchCases<T> = () => ({
        case: (value: T, result: () => React.ReactNode) => {
            possibleCases.push({ value: value, result });

            return getSwitchCases();
        },
        default: (result: () => React.ReactNode) => {
            defaultResult = result;

            return getSwitchCases();
        },
    })
    
    // getSwitchCases is recursive and will add all possible cases to the possibleCases array and sets defaultResult.
    cases(getSwitchCases());

    // Check if one of the cases is met
    for(const possibleCase of possibleCases) {
        if (possibleCase.value === value) {
            return possibleCase.result();
        }
    }

    // Check if the default case is defined
    if (defaultResult) {
        // Typescript wrongly assumes that defaultResult is always null.
        var fixedDefaultResult = defaultResult as (() => React.ReactNode);

        return fixedDefaultResult();
    }

    // None of the cases were met and default was not defined.
    return undefined;
}

其他回答

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>

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;

这个助手应该可以做到这一点。 使用示例:

{componentSwitch(3, (switcher => switcher
    .case(1, () =>
        <p>It is one</p>
    )
    .case(2, () =>
        <p>It is two</p>
    )
    .default(() =>
        <p>It is something different</p>
    )
))}

助手:

interface SwitchCases<T> {
    case: (value: T, result: () => React.ReactNode) => SwitchCases<T>;
    default: (result: () => React.ReactNode) => SwitchCases<T>;
}

export function componentSwitch<T>(value: T, cases: (cases: SwitchCases<T>) => void) {

    var possibleCases: { value: T, result: () => React.ReactNode }[] = [];
    var defaultResult: (() => React.ReactNode) | null = null;

    var getSwitchCases: () => SwitchCases<T> = () => ({
        case: (value: T, result: () => React.ReactNode) => {
            possibleCases.push({ value: value, result });

            return getSwitchCases();
        },
        default: (result: () => React.ReactNode) => {
            defaultResult = result;

            return getSwitchCases();
        },
    })
    
    // getSwitchCases is recursive and will add all possible cases to the possibleCases array and sets defaultResult.
    cases(getSwitchCases());

    // Check if one of the cases is met
    for(const possibleCase of possibleCases) {
        if (possibleCase.value === value) {
            return possibleCase.result();
        }
    }

    // Check if the default case is defined
    if (defaultResult) {
        // Typescript wrongly assumes that defaultResult is always null.
        var fixedDefaultResult = defaultResult as (() => React.ReactNode);

        return fixedDefaultResult();
    }

    // None of the cases were met and default was not defined.
    return undefined;
}

改进了一点 马特·韦的回答。

export const Switch = ({ test, children }) => { const defaultResult = children.find((child) => child.props.default) || null; const result = children.find((child) => child.props.value === test); return result || defaultResult; }; export const Case = ({ children }) => children; const color = getColorFromTheMostComplexFnEver(); <Switch test={color}> <Case value="Green">Forest</Case> <Case value="Red">Blood</Case> <Case default>Predator</Case> </Switch> <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>

React组件中的Switch-Case语句可以如下使用:

<div  id="time-list">
{   
    (() => {
        switch (groupByFilterId) {
            case 0:/*Case 0 */
                return (
                    <div>Case 0</div>
                )
               break;
           case 1: /*Case 1 */
           return ( 
            <div>Case 1</div>
            )
            break;
           case 2:/*Case 2 */
           return ( 
            <div>Case 2</div>
            )
            break;
        }
     })()}

      
       
    
    </div>