Reactã®<code>cloneElement</code>ã«ã€ããŠããã®æ©èœãäœ¿ãæ¹ãé«åºŠãªèŠçŽ å€æŽãã¿ãŒã³ãå æ¬çã«è§£èª¬ããŸããã³ã³ããŒãã³ããåçã«é©å¿ã»æ¡åŒµããæè»æ§ãšåå©çšæ§ãé«ããæ¹æ³ãåŠã³ãŸãããã
React cloneElement: èŠçŽ å€æŽãã¿ãŒã³ã®ç¿åŸ
Reactã®cloneElementã¯ãæ¢åã®ReactèŠçŽ ãæäœããã³æ¡åŒµããããã®åŒ·åã§ãããªããèŠèœãšãããã¡ãªAPIã§ããããã«ãããæ¢åã®ReactèŠçŽ ã«åºã¥ããŠæ°ããReactèŠçŽ ãäœæãããã®ããããã£ïŒpropsïŒãšåèŠçŽ ãç¶æ¿ãã€ã€ãæ°ããããããã£ãåèŠçŽ ãäžæžããŸãã¯è¿œå ããããšãã§ããŸããããã¯ãåçãªã³ã³ããŒãã³ãæ§æãé«åºŠãªã¬ã³ããªã³ã°æè¡ãããã³ã³ã³ããŒãã³ãã®åå©çšæ§ã®åäžã«ç¡éã®å¯èœæ§ããããããŸãã
ReactèŠçŽ ãšã³ã³ããŒãã³ããçè§£ãã
cloneElementã«æ·±ãå
¥ãåã«ãReactã®èŠçŽ ïŒelementsïŒãšã³ã³ããŒãã³ãïŒcomponentsïŒã®æ ¹æ¬çãªéããçè§£ããããšãäžå¯æ¬ ã§ãã
- ReactèŠçŽ ïŒElementsïŒ: ãããã¯ãç»é¢ã«è¡šç€ºããããã®ãèšè¿°ãããã¬ãŒã³ãªJavaScriptãªããžã§ã¯ãã§ãã軜éã§äžå€ã§ããReactãå®éã®DOMããŒããäœæããããã®èšèšå³ãšèããŠãã ããã
- Reactã³ã³ããŒãã³ãïŒComponentsïŒ: ãããã¯ãReactèŠçŽ ãè¿ãåå©çšå¯èœãªã³ãŒãã®å¡ã§ãã颿°ã³ã³ããŒãã³ãïŒJSXãè¿ã颿°ïŒãŸãã¯ã¯ã©ã¹ã³ã³ããŒãã³ãïŒ
React.Componentãæ¡åŒµããã¯ã©ã¹ïŒã®ããããã§ãã
cloneElementã¯ReactèŠçŽ ã«çŽæ¥äœçšãããããã®ããããã£ãæ£ç¢ºã«å¶åŸ¡ããããšãå¯èœã«ããŸãã
cloneElementãšã¯ïŒ
React.cloneElement()颿°ã¯ãæåã®åŒæ°ãšããŠReactèŠçŽ ãåããå
ã®èŠçŽ ã®ã·ã£ããŒã³ããŒã§ããæ°ããReactèŠçŽ ãè¿ããŸãããã®åŸããªãã·ã§ã³ã§æ°ããpropsãšåèŠçŽ ãã¯ããŒã³ãããèŠçŽ ã«æž¡ãããšã§ãå
ã®èŠçŽ ã®ããããã£ã广çã«äžæžããŸãã¯æ¡åŒµããããšãã§ããŸãã
åºæ¬çãªæ§æã¯æ¬¡ã®ãšããã§ãã
React.cloneElement(element, [props], [...children])
element: ã¯ããŒã³ããReactèŠçŽ ãprops: å ã®èŠçŽ ã®propsãšããŒãžããæ°ããpropsãå«ããªãã·ã§ã³ã®ãªããžã§ã¯ããå ã®èŠçŽ ã«ãã§ã«ååšããpropãããå Žåãæ°ããå€ããããäžæžãããŸããchildren: ã¯ããŒã³ãããèŠçŽ ã®ãªãã·ã§ã³ã®æ°ããåèŠçŽ ãæäŸãããå Žåããããã¯å ã®èŠçŽ ã®åèŠçŽ ã眮ãæããŸãã
åºæ¬çãªäœ¿çšæ³: 倿Žãããpropsã§ã®ã¯ããŒã³
ç°¡åãªäŸããå§ããŸãããããã¿ã³ã³ã³ããŒãã³ãããããšããŸãã
function MyButton(props) {
return <button className="my-button" onClick={props.onClick}>
{props.children}
</button>;
}
ã§ã¯ããã®ãã¿ã³ã®å°ãç°ãªãããŒãžã§ã³ãäœæããããšããŸããããšãã°ãå¥ã®onClickãã³ãã©ãŒã远å ã®ã¹ã¿ã€ãªã³ã°ãæã€ãã®ãªã©ã§ããæ°ããã³ã³ããŒãã³ããäœæããããšãã§ããŸãããcloneElementã¯ããç°¡æœãªè§£æ±ºçãæäŸããŸãã
import React from 'react';
function App() {
const handleClick = () => {
alert('Button clicked!');
};
const clonedButton = React.cloneElement(
<MyButton>Click Me</MyButton>,
{
onClick: handleClick,
style: { backgroundColor: 'lightblue' }
}
);
return (
<div>
{clonedButton}
</div>
);
}
ãã®äŸã§ã¯ã<MyButton>èŠçŽ ãã¯ããŒã³ããæ°ããonClickãã³ãã©ãŒãšstyleãããããæäŸããŠããŸããã¯ããŒã³ããããã¿ã³ã¯ãå
ã®ãã¿ã³ã®classNameãšåèŠçŽ ãç¶æ¿ãã€ã€ãæ°ããæ©èœãšã¹ã¿ã€ãªã³ã°ãæã€ããšã«ãªããŸãã
cloneElementã§åèŠçŽ ãä¿®æ£ãã
cloneElementã¯ãèŠçŽ ã®åèŠçŽ ãä¿®æ£ããããã«ã䜿çšã§ããŸããããã¯ãæ¢åã®ã³ã³ããŒãã³ãã®åäœãã©ãããŸãã¯æ¡åŒµãããå Žåã«ç¹ã«åœ¹ç«ã¡ãŸãã
ã³ã³ããå ã«åèŠçŽ ãã¬ã³ããªã³ã°ããã¬ã€ã¢ãŠãã³ã³ããŒãã³ããããã·ããªãªãèããŠã¿ãŸãããã
function Layout(props) {
return <div className="layout">{props.children}</div>;
}
ããã§ãã¬ã€ã¢ãŠãå
ã®ååèŠçŽ ã«ç¹å¥ãªã¯ã©ã¹ã远å ããããšããŸããããã¯cloneElementã䜿çšããŠå®çŸã§ããŸãã
import React from 'react';
function App() {
const children = React.Children.map(
<Layout>
<div>Child 1</div>
<span>Child 2</span>
</Layout>.props.children,
child => {
return React.cloneElement(child, {
className: child.props.className ? child.props.className + ' special-child' : 'special-child'
});
}
);
return <Layout>{children}</Layout>;
}
ãã®äŸã§ã¯ãReact.Children.mapã䜿çšããŠ<Layout>ã³ã³ããŒãã³ãã®åèŠçŽ ãå埩åŠçããŠããŸããååèŠçŽ ã«ã€ããŠããããã¯ããŒã³ããspecial-childã¯ã©ã¹ã远å ããŸããããã«ããã<Layout>ã³ã³ããŒãã³ãèªäœãçŽæ¥å€æŽããããšãªããåèŠçŽ ã®èŠãç®ãåäœãä¿®æ£ã§ããŸãã
é«åºŠãªãã¿ãŒã³ãšãŠãŒã¹ã±ãŒã¹
cloneElementã¯ãä»ã®Reactã®æŠå¿µãšçµã¿åãããããšã§ãé«åºŠãªã³ã³ããŒãã³ããã¿ãŒã³ãäœæããéã«ä¿¡ããããªãã»ã©åŒ·åã«ãªããŸãã
1. ã³ã³ããã¹ãã¬ã³ããªã³ã°
cloneElementã䜿çšããŠãåã³ã³ããŒãã³ãã«ã³ã³ããã¹ãå€ã泚å
¥ã§ããŸããããã¯ãããããããªãªã³ã°ïŒã³ã³ããŒãã³ãããªãŒã®è€æ°ã®ã¬ãã«ãä»ããŠãããããæž¡ãããšïŒãªãã§ãæ·±ããã¹ããããã³ã³ããŒãã³ãã«èšå®ãŸãã¯ç¶æ
æ
å ±ãæäŸãããå Žåã«ç¹ã«åœ¹ç«ã¡ãŸãã
import React, { createContext, useContext } from 'react';
const ThemeContext = createContext('light');
function ThemedButton(props) {
const theme = useContext(ThemeContext);
return <button style={{ backgroundColor: theme === 'dark' ? 'black' : 'white', color: theme === 'dark' ? 'white' : 'black' }} {...props} />;
}
function App() {
return (
<ThemeContext.Provider value="dark">
<ThemedButton>Click Me</ThemedButton>
</ThemeContext.Provider>
);
}
ããã§ã`ThemedButton`å ã§çŽæ¥ã³ã³ããã¹ãã䜿çšãã代ããã«ã`ThemedButton`ãã¯ããŒã³ããã³ã³ããã¹ãå€ããããããšããŠæ³šå ¥ããé«éã³ã³ããŒãã³ããæã€ããšãã§ããŸãã
import React, { createContext, useContext } from 'react';
const ThemeContext = createContext('light');
function ThemedButton(props) {
return <button style={{ backgroundColor: props.theme === 'dark' ? 'black' : 'white', color: props.theme === 'dark' ? 'white' : 'black' }} {...props} />;
}
function withTheme(WrappedComponent) {
return function WithTheme(props) {
const theme = useContext(ThemeContext);
return React.cloneElement(WrappedComponent, { ...props, theme });
};
}
const EnhancedThemedButton = withTheme(<ThemedButton>Click Me</ThemedButton>);
function App() {
return (
<ThemeContext.Provider value="dark">
<EnhancedThemedButton />
</ThemeContext.Provider>
);
}
2. æ¡ä»¶ä»ãã¬ã³ããªã³ã°ãšãã³ã¬ãŒã·ã§ã³
cloneElementã䜿çšããŠãç¹å®ã®æ¡ä»¶ã«åºã¥ããŠã³ã³ããŒãã³ããæ¡ä»¶ä»ãã§ã¬ã³ããªã³ã°ãããè£
食ãããã§ããŸããããšãã°ãããŒã¿ããŸã ãã§ãããããŠããå Žåãã³ã³ããŒãã³ããããŒãã£ã³ã°ã€ã³ãžã±ãŒã¿ãŒã§ã©ãããããå ŽåããããŸãã
import React from 'react';
function MyComponent(props) {
return <div>{props.data}</div>;
}
function LoadingIndicator() {
return <div>Loading...</div>;
}
function App() {
const isLoading = true; // Simulate loading state
const data = "Some data";
const componentToRender = isLoading ? <LoadingIndicator /> : <MyComponent data={data} />;
return (<div>{componentToRender}</div>);
}
cloneElementã䜿çšããŠã`MyComponent`ã®*åšãã«*ããŒãã£ã³ã°ã€ã³ãžã±ãŒã¿ãŒãåçã«æ³šå
¥ã§ããŸãã
import React from 'react';
function MyComponent(props) {
return <div>{props.data}</div>;
}
function LoadingIndicator(props) {
return <div>Loading... {props.children}</div>;
}
function App() {
const isLoading = true; // Simulate loading state
const data = "Some data";
const componentToRender = isLoading ? React.cloneElement(<LoadingIndicator><MyComponent data={data} /></LoadingIndicator>, {}) : <MyComponent data={data} />;
return (<div>{componentToRender}</div>);
}
ãããã¯ãå¥ã®ããŒãã£ã³ã°ã€ã³ãžã±ãŒã¿ãŒã䜿çšãã代ããã«ãcloneElementãçŽæ¥äœ¿çšããŠ`MyComponent`ãã¹ã¿ã€ãªã³ã°ã§ã©ããããããšãã§ããŸãã
import React from 'react';
function MyComponent(props) {
return <div>{props.data}</div>;
}
function App() {
const isLoading = true; // Simulate loading state
const data = "Some data";
const componentToRender = isLoading ? React.cloneElement(<MyComponent data={data} />, {style: {opacity: 0.5}}) : <MyComponent data={data} />;
return (<div>{componentToRender}</div>);
}
3. Render Propsã«ããã³ã³ããŒãã³ãæ§æ
cloneElementã¯ãrender propsãšçµã¿åãããŠäœ¿çšââããããšã§ãæè»ã§åå©çšå¯èœãªã³ã³ããŒãã³ããäœæã§ããŸããrender propã¯ãã³ã³ããŒãã³ããäœããã¬ã³ããªã³ã°ããããã«äœ¿çšãã颿°ããããã§ããããã«ãããã³ã³ããŒãã³ãã®å®è£
ãçŽæ¥å€æŽããããšãªããã«ã¹ã¿ã ã¬ã³ããªã³ã°ããžãã¯ãã³ã³ããŒãã³ãã«æ³šå
¥ã§ããŸãã
import React from 'react';
function DataProvider(props) {
const data = ["Item 1", "Item 2", "Item 3"]; // Simulate data fetching
return props.render(data);
}
function App() {
return (
<DataProvider
render={data => (
<ul>
{data.map(item => (
<li key={item}>{item}</li>
))}
</ul>
)}
/>
);
}
`cloneElement`ã䜿çšãããšãrender propã«ãã£ãŠè¿ãããèŠçŽ ãåçã«å€æŽã§ããŸããããšãã°ãåãªã¹ãã¢ã€ãã ã«ç¹å®ã®ã¯ã©ã¹ã远å ãããå ŽåããããŸãã
import React from 'react';
function DataProvider(props) {
const data = ["Item 1", "Item 2", "Item 3"]; // Simulate data fetching
return props.render(data);
}
function App() {
return (
<DataProvider
render={data => {
const listItems = data.map(item => <li key={item}>{item}</li>);
const enhancedListItems = listItems.map(item => React.cloneElement(item, { className: "special-item" }));
return <ul>{enhancedListItems}</ul>;
}}
/>
);
}
ãã¹ããã©ã¯ãã£ã¹ãšèæ ®äºé
- äžå€æ§:
cloneElementã¯æ°ããèŠçŽ ãäœæããå ã®èŠçŽ ã¯å€æŽããŸãããããã¯ãReactã®ã³ã¢ååã§ããReactèŠçŽ ã®äžå€æ§ãç¶æããããã«äžå¯æ¬ ã§ãã - Key Props: åèŠçŽ ã倿Žããéã¯ã
keyããããã«æ³šæããŠãã ãããèŠçŽ ãåçã«çæããŠããå ŽåãReactãDOMãå¹ççã«æŽæ°ã§ããããã«ãåèŠçŽ ã«äžæã®keyãããããšã確èªããŠãã ããã - ããã©ãŒãã³ã¹:
cloneElementã¯äžè¬çã«å¹ççã§ãããé床ãªäœ¿çšã¯ããã©ãŒãã³ã¹ã«åœ±é¿ãäžããå¯èœæ§ããããŸããç¹å®ã®ãŠãŒã¹ã±ãŒã¹ã«æãé©åãªãœãªã¥ãŒã·ã§ã³ã§ãããã©ãããæ€èšããŠãã ãããæã«ã¯ãæ°ããã³ã³ããŒãã³ããäœæããæ¹ãã·ã³ãã«ã§ããã©ãŒãã³ã¹ãè¯ãå ŽåããããŸãã - ä»£æ¿æ¡: ç¹å®ã®ã·ããªãªã§ã¯ãç¹ã«è€æ°ã®ã³ã³ããŒãã³ãéã§å€æŽããžãã¯ãåå©çšããå¿ èŠãããå Žåãé«éã³ã³ããŒãã³ãïŒHOCïŒãRender Propsã®ãããªä»£æ¿æ¡ãæ€èšããŠãã ããã
- Prop Drilling:
cloneElementã¯ããããã®æ³šå ¥ã«åœ¹ç«ã¡ãŸãããContext APIãReduxã®ãããªé©åãªç¶æ 管çãœãªã¥ãŒã·ã§ã³ã®ä»£æ¿ãšããŠé床ã«äœ¿çšããããšã¯é¿ããŠãã ããããããã¯è€éãªç¶æ å ±æã·ããªãªãåŠçããããã«èšèšãããŠããŸãã
å®äžçã®äŸãšã°ããŒãã«ãªå¿çš
- Eã³ããŒã¹ãã©ãããã©ãŒã : åšåº«ã¬ãã«ãããã¢ãŒã·ã§ã³ãã£ã³ããŒã³ã«åºã¥ããŠãååãªã¹ãã³ã³ããŒãã³ãã«ååãããžïŒäŸïŒãã»ãŒã«ãããæ°çãïŒãåçã«è¿œå ããããããã®ãããžã¯ãç°ãªãæåçå¯©çŸæ§ïŒäŸïŒå欧åžå Žåãã®ããããªã¹ããã¶ã€ã³ãã©ãã³ã¢ã¡ãªã«åžå Žåãã®é®®ãããªè²ïŒã«åãããŠèŠèŠçã«èª¿æŽã§ããŸãã
- åœéåããããŠã§ããµã€ã: ãŠãŒã¶ãŒã®ãã±ãŒã«ã«åºã¥ããŠãããã¹ãã³ã³ããŒãã³ãã«èšèªåºæã®å±æ§ïŒäŸïŒã¢ã©ãã¢èªãããã©ã€èªã®ãããªå³ããå·Šãžã®èšèªã®
dir="rtl"ïŒãæ³šå ¥ãããããã«ãããã°ããŒãã«ãªãªãŒãã£ãšã³ã¹ã«å¯ŸããŠé©åãªããã¹ãã®é 眮ãšã¬ã³ããªã³ã°ãä¿èšŒãããŸãã - ã¢ã¯ã»ã·ããªãã£æ©èœ: ãŠãŒã¶ãŒèšå®ãã¢ã¯ã»ã·ããªãã£ç£æ»ã«åºã¥ããŠãUIã³ã³ããŒãã³ãã«ARIA屿§ïŒäŸïŒ
aria-labelãaria-hiddenïŒãæ¡ä»¶ä»ãã§è¿œå ãããããã«ãããWCAGã¬ã€ãã©ã€ã³ã«æºæ ããé害ãæã€ãŠãŒã¶ãŒã«ãšã£ãŠãŠã§ããµã€ããããã¢ã¯ã»ã¹ãããããªããŸãã - ããŒã¿èŠèŠåã©ã€ãã©ãª: ããŒã¿å€ããŠãŒã¶ãŒéžæã«åºã¥ããŠããã£ãŒãèŠçŽ ïŒäŸïŒããŒãç·ãã©ãã«ïŒãã«ã¹ã¿ã ã¹ã¿ã€ã«ãã€ã³ã¿ã©ã¯ã·ã§ã³ã§å€æŽãããããã«ãããç°ãªãåæããŒãºã«å¯Ÿå¿ããåçã§ã€ã³ã¿ã©ã¯ãã£ããªããŒã¿èŠèŠåãå¯èœã«ãªããŸãã
- ã³ã³ãã³ã管çã·ã¹ãã ïŒCMSïŒ: ã³ã³ãã³ãã¿ã€ããå ¬éãã£ãã«ã«åºã¥ããŠãã«ã¹ã¿ã ã¡ã¿ããŒã¿ããã©ããã³ã°ãã¯ã»ã«ãã³ã³ãã³ãã³ã³ããŒãã³ãã«è¿œå ãããããã«ããããã现ããã³ã³ãã³ãåæãšããŒãœãã©ã€ãºããããŠãŒã¶ãŒãšã¯ã¹ããªãšã³ã¹ãå¯èœã«ãªããŸãã
çµè«
React.cloneElementã¯ãReactéçºè
ã«ãšã£ãŠè²ŽéãªããŒã«ã§ããæ¢åã®ReactèŠçŽ ã倿Žããã³æ¡åŒµããããã®æè»ã§åŒ·åãªæ¹æ³ãæäŸããåçãªã³ã³ããŒãã³ãæ§æãšé«åºŠãªã¬ã³ããªã³ã°æè¡ãå¯èœã«ããŸãããã®æ©èœãšéçãçè§£ããããšã§ãcloneElementãæŽ»çšããŠãããåå©çšå¯èœã§ä¿å®ãããããé©å¿æ§ã®é«ãReactã¢ããªã±ãŒã·ã§ã³ãäœæã§ããŸãã
æäŸãããäŸã詊ããŠãcloneElementãããªãã®Reactãããžã§ã¯ããã©ã®ããã«åŒ·åã§ããããæ¢ã£ãŠã¿ãŠãã ãããããããŒã³ãŒãã£ã³ã°ïŒ