ããã«ã¡ã¯ãç§ã¯æè¿React Hookãç 究ããŠããŸããããã¯çŽ æŽãããã§ãã
ããããç§ã«ã¯åé¡ããããŸããReactHookã®ããã¥ã¡ã³ããšã°ãŒã°ã«ã§åé¡ã解決ããããã®é©åãªçããèŠã€ãããŸããã§ããã
useEffectã®é¢æ°ãšé¢æ°ã³ã³ããŒãã³ããäžç·ã«äœ¿çšãããšã以äžã«ç€ºãããã«ãuseEffectã®äŸåé¢ä¿ãæå®ããŠããªããšããèŠåã衚瀺ãããŸããã
ç§ã®åé¡ã解決ããæ¹æ³ã¯ãããŸããïŒ ç§ã¯é·ãéããã«ã€ããŠèããŠããŸããã
çŸåšã®åäœã¯äœã§ããïŒ
React Hook useEffect has a missing dependency: 'setCenterPosition'. Either include it or remove the dependency array. (react-hooks/exhaustive-deps)
codesandboxã®ãããªããïŒ
https://codesandbox.io/s/trusting-kowalevski-oet4b
ã©ããªè§£æ±ºçã§ããããããšãã
ã³ãŒã
function App() {
const [elePositionArr, setElePositionArr] = useState([
{ left: 0, top: 0 },
{ left: 0, top: 0 },
{ left: 0, top: 0 }
]);
const stageRef = useRef(null);
const Stage = useRef({ w: 0, h: 0 });
const currentIndex = useRef(0);
useEffect(() => {
// Record the size of the stage
const stageW = stageRef.current.scrollWidth;
const stageH = stageRef.current.scrollHeight;
Stage.current = { w: stageW, h: stageH };
const index = Math.floor(Math.random() * 3);
currentIndex.current = index;
setCenterPosition(index);
}, []);
// Centering a block element
function setCenterPosition(index) {
let cacheEle = elePositionArr;
// calc center postion
const centerOfLeft = Stage.current.w / 2 - 25;
const centerOfTop = Stage.current.h / 2 - 25;
cacheEle = cacheEle.map((item, i) => {
const randomWNum = Math.floor(Math.random() * Stage.current.w) - 50;
const randomHNum = Math.floor(Math.random() * Stage.current.h) - 50;
const randomLeft = randomWNum <= 50 ? 50 : randomWNum;
const randomTop = randomHNum <= 50 ? 50 : randomHNum;
let newItem;
if (index === i) {
newItem = { left: centerOfLeft, top: centerOfTop };
} else {
newItem = { left: randomLeft, top: randomTop };
}
return newItem;
});
setElePositionArr(cacheEle);
}
function handleClickLi(index) {
if (currentIndex.current !== index) {
setCenterPosition(index);
currentIndex.current = index;
}
}
return (
<div className="container">
<div className="stage" ref={stageRef}>
{elePositionArr.map((item, index) => (
<div className="ele" key={index} style={item}>
{index}
</div>
))}
</div>
<ul className="nav">
{elePositionArr.map((item, index) => (
<li
className={currentIndex.current === index ? "active-li" : ""}
onClick={() => {
handleClickLi(index);
}}
key={"li" + index}
>
{index}
</li>
))}
</ul>
</div>
);
}
ããã¯ããªãã®è³ªåã«çããã¯ãã§ãïŒ
https://reactjs.org/docs/hooks-faq.html#is -it-safe-to-omit-functions-from-the-list-of-dependencies
ããã¯ããªãã®è³ªåã«çããã¯ãã§ãïŒ
https://reactjs.org/docs/hooks-faq.html#is -it-safe-to-omit-functions-from-the-list-of-dependencies
@gaearon
ç§ã®åé¡ã解決ããŸããã§ãããç§ã®åé¡ã¯ããç¹å¥ã§ããç§ã®å®è¡functionsetElePositionArrã¯componentDidMountãšhandleClickã§èµ·åãããã®ã§ãããReactHooké¢æ°ãç§ã®èŠä»¶ãæºãããŠããªãã®ã§èŠåã衚瀺ãããŸãã
ç§ã®è³ªåã¯ïŒReactããã¯ã¯useEffectããã³é¢æ°ã³ã³ããŒãã³ãã®é¢æ°ãsetStateæäœã«åŒã³åºãããšãã§ããŸãããïŒ
2çªç®ã®è³ªåã«çããããããã«ãéãããŸãŸã«ããŠãããŸãã
åãESLintèŠåã衚瀺ãããŸãããç§ã®å Žåãã³ã³ããŒãã³ããããŠã³ãããããšãã«éåæåŒã³åºããè¡ããããšæããŸãã
const ManageTagsModalBody: React.FC<IProps> = ({ children, getTags }) => {
useEffect(() => {
getTags();
}, []);
return <div>{children}</div>;
};
Line 12: React Hook useEffect has a missing dependency: 'getTags'. Either include it or remove the dependency array. If 'getTags' changes too often, find the parent component that defines it and wrap that definition in useCallback react-hooks/exhaustive-deps
ManageTagsModalBody
ã¯ããŒã¿ã«äŸåãããã³ã³ããŒãã³ããã¬ã³ããªã³ã°ããããã³ã«ããŒã¿ãããŒãããããã®ã©ãããŒãšããŠã®ã¿äœ¿çšãããŸãã children
ã³ã³ããŒãã³ããgetTags
ããã§ããããããŒã¿ã䜿çšããŠããããšã¯æ³šç®ã«å€ããŸãã
äŸåé¢ä¿ã®ãªã¹ãã«äœãè¿œå ããã°ãããããããŸããã
説æã«ãèå³ããããŸãã
React Hook useEffectã«ã¯ãäŸåé¢ä¿ããããŸããïŒ 'dispatch'ã
useEffect(() => {
axios.get('http://localhost:8000/api/future-registrations')
.then((result) => {
dispatch(initRegistrationsAction(result.data));
});
}, []);
ããã§åãåé¡ã å¥åŠãªã«ãŒã«ã
ãã£ã¡ãäžç·ã https://github.com/facebook/react/issues/15865#issuecomment -506503377ã®ããã«ç°¡åã§ãïŒ
useEffect(() => {
dispatch(fetchPosts());
}, []);
ãã®èŠåãæå¶ããæ¹æ³ã¯ãããŸããïŒ
èŠåã¡ãã»ãŒãžã§ç€ºåãããŠããããã«ãããªãã¯ãã®ããã«ããããšãã§ããŸã
const initFetch = useCallback(() => {
dispatch(fetchPosts());
}, [dispatch]);
useEffect(() => {
initFetch();
}, [initFetch]);
@faywayã®å ŽåãinitFetchãšãã£ã¹ãããå€ãå€æŽããããšãuseEffectã®ã³ãŒã«ããã¯ãå®è¡ãããŸãã
圌ã¯äžåºŠã³ãŒã«ããã¯ãå®è¡ããã
@shkyungç§ã®å Žåã initFetchã¯åå ïŒã¹ãã¢ïŒãå€æŽããŸããããã£ã¹ããããå€æŽããŸããã
å€åããã¯ãã®ããã«ããããšãã§ããŸã
const setCenterPosition = useRef(null)
setCenterPosition.current = useCallback( ()=>{} ,[deps])
effect(()=>{ setCenterPosition.current() },[setCenterPosition,otherDeps])
ãã®å€æŽã¯ãççŽã«èšã£ãŠãå°ãã°ãããŠéå¹æã®ããã§ãã ãããã以åã®ããŒãžã§ã³ã«ããŒã«ããã¯ããŠããããèããããŠãã ããã
åãåé¡ããããŸãã componentDidMountã§ã®ã¿ãã§ãããèµ·åãããã é åã«äŸåé¢ä¿ãè¿œå ãããšããšã³ããã€ã³ãã«ç¹°ãè¿ããããããŸãã
React Hook useEffectã«ã¯ãäŸåé¢ä¿ããããŸããïŒ 'dispatch'ã
const [state, dispatch] = useReducer(reducer, initialState);
const { count, step } = state;
useEffect(() => {
const id = setInterval(() => {
dispatch({ type: 'tick' }); // Instead of setCount(c => c + step);
}, 1000);
return () => clearInterval(id);
}, [dispatch]);
ããã¯éåžžã«äžè¬çãªãŠãŒã¹ã±ãŒã¹ã®ããã§ããçŸåšã®ãããžã§ã¯ãã§ééãããã®ã§ãã
ãšãã§ã¯ãããã¯ã1åã ãå®è¡ãããã®ã§ãããèµ·åæã®ç¶æ
ã ããæ°ã«ããŸãããäŸåé¢ä¿ããããŸãã çŸåšäœ¿çšäž
// eslint-disable-next-line react-hooks/exhaustive-deps
ã
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ããã¯éåžžã«äžè¬çãªãŠãŒã¹ã±ãŒã¹ã®ããã§ããçŸåšã®ãããžã§ã¯ãã§ééãããã®ã§ãã
ãšãã§ã¯ãããã¯ã1åã ãå®è¡ãããã®ã§ãããèµ·åæã®ç¶æ ã ããæ°ã«ããŸãããäŸåé¢ä¿ããããŸãã çŸåšäœ¿çšäž
// eslint-disable-next-line react-hooks/exhaustive-deps
ã
ãªã³ãã£ã³ã°ã«ãŒã«ããªãã«ããŸããããã®å Žåã¯ãªãã«ããå¿ èŠããªãã®ãããã§ãããã
Lintãéããããšã¯äžæçãªè§£æ±ºçã«ãããããã®åé¡ã®éµã¯ããã¯ãç解ããã®ã«ååã§ã¯ãããŸããã
ããã§åãåé¡ã useEffectïŒïŒå ã§é¢æ°ã1åèµ·åãããã£ãã®ã§ããã2çªç®ã®ãã©ã¡ãŒã¿ãŒãšããŠ[]ãæå®ãããšãå¿ èŠãªåŠçãå®è¡ãããŸããããã®èŠåã衚瀺ããç¶ããŸãã
æ°ãããããžã§ã¯ãã§ä»æ¥ãŸã§èŠãããšããªãã®ã§ããã®ãããªå¥åŠãªèŠåã ããã¯ãã³ã³ããŒãã³ããããŠã³ãããããšãã«1åã ãåŒã³åºããããšãããŠãŒã¹ã±ãŒã¹ãå°ç¡ãã«ããŸãã lintèŠåãç¡èŠãã以å€ã«ãåé¿çã¯ãªãããã§ãã
ããã«2ã»ã³ãå ¥ãããã®ã§ããã ç¹ã«ãAxiosã䜿çšããŠãããã¯ãŒã¯ãªã¯ãšã¹ãããã£ã³ã»ã«ããå Žåã å¿ èŠã«å¿ããŠå¥ã®åé¡ãäœæããŸããããã®åé¡ãçŽæ¥èªåã«åœ±é¿ãäžããŠãããšæããŸããã ã ããç§ã®useApiããã¯ã¯æ¬¡ã®ãšããã§ã-
import axios, { AxiosInstance } from "axios";
import axiosRetry from "axios-retry";
import { FetchEnv } from "../../utilities";
import { useStorage } from "../useStorage";
export const useApi = ({ isAuth = false, retries = 3 } = {}) => {
const cancelToken = axios.CancelToken.source();
const { getItem } = useStorage();
const getBaseUrl = () => {
return FetchEnv({
defaultValue: "http://api.example.com",
key: "API_URI"
});
};
const authorizedClient = (client: AxiosInstance) => {
const session = getItem("SESSION", "sessionStorage");
const hasAccessToken = Boolean(session.tokens.accessToken);
if (isAuth && !hasAccessToken) {
console.error("No access token found to initiate authorized request.");
return client;
} else {
client.defaults.headers[
"Authorization"
] = `Bearer ${session.tokens.accessToken}`;
return client;
}
};
const buildFetch = (): AxiosInstance => {
const client = axios.create({
baseURL: getBaseUrl(),
cancelToken: cancelToken.token
});
axiosRetry(client, { retries });
return isAuth ? authorizedClient(client) : client;
};
return {
cancelRequest: cancelToken.cancel,
fetch: buildFetch()
};
};
ã³ã³ããŒãã³ãå ã§ãã®ããã¯ã䜿çšããã«ã¯ã以äžã®ããã«å®çŸ©ããã ãã§ãããŠã³ãæãuseEffectå ãã€ãã³ããã³ãã©ãŒã®äžéšãªã©ã®ããããã§ãèªèšŒæžã¿ãšæªèªèšŒã®äž¡æ¹ã®åŒã³åºããè¡ãããšãã§ããŸããcancelRequestã¯ãçæãããäžæã®ãã£ã³ã»ã«ããŒã¯ã³ã§ããããã¯ããã®ã³ã³ããŒãã³ãã«é¢é£ããããã§ãããaxiosã€ã³ã¹ã¿ã³ã¹ãšãã¢ã«ãªã£ãŠããŸãã
const { cancelRequest, fetch } = useApi();
äœããã®çç±ã§ãã®ã³ã³ããŒãã³ããããŠã³ã解é€ãããå Žåã以äžãåŒã³åºãããŸãã
useEffect(() => {
return () => {
cancelRequest("Auth network request cancelled");
};
}, []);
çŸåšãå®å šã«æ©èœããŠããŸãã ãã ããèŠåãé©çšããããšïŒcancelRequestãuseEffectäŸåé¢ä¿ãšããŠé 眮ïŒãfetchã¡ãœãããåŒã³åºããããšããã«ãããã¯ãŒã¯èŠæ±ããã£ã³ã»ã«ãããŸãã ä»»æã®ã¢ããã€ã¹ãããã ããã°å¹žãã§ãããçŸæç¹ã§ã®å¯äžã®è§£æ±ºçã¯ãts-lintã§ãããç¡å¹ã«ããããšã§ã...
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ãã®ããäžã®@ Stoner609ã®äŸã§ã¯ãã¿ã€ãã³ã°ã³ãŒããuseCallbackããã¯ã«å«ããå¿ èŠãããã®ã§ã¯ãªãããšæããŸããã ãã ããäŸåé¢ä¿ãšããŠé¢æ°ïŒéçã§ããå¿ èŠããããŸãïŒãæã€ããšã¯ãŸã å¥åŠã§ãã
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ã³ã³ããŒãã³ãã®ããŒãæã«é¢æ°ã1åã ãå®è¡ãããã©ã¡ãŒã¿ãŒãåã蟌ãå Žåã¯ãuseRefã䜿çšããŠèŠåãåé¿ã§ããŸãã ãã®ãããªãã®ãæ©èœããŸãïŒ
const InitialPropA= useRef(propA);
useEffect(() => {
myFunction(InitialPropA.current);
}, [myFunction, InitialPropA]);
èŠåã¡ãã»ãŒãžã§ç€ºåãããŠããããã«ãããªãã¯ãã®ããã«ããããšãã§ããŸã
const initFetch = useCallback(() => { dispatch(fetchPosts()); }, [dispatch]); useEffect(() => { initFetch(); }, [initFetch]);
ç§ããã®æ©ç¥ã«å¯ãã è¿ä¿¡ãæ°ã«å
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const initFetch = useCallback(() => { dispatch(fetchPosts()); }, [dispatch]); useEffect(() => { initFetch(); }, [initFetch]);
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å
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React Hook useEffectã«ã¯ãäŸåé¢ä¿ããããŸããïŒ 'props'ã ãããããå°éå ·ãã®ã§å¥œãŸããä¿®æ£ãuseEffectã³ãŒã«ã®ãå°éå ·ããªããžã§ã¯ãã®å€åŽãdestructureãšuseEffectå ã®ãããã®ç¹å®ã®å°éå ·åå¿-ããã¯/ç¶²çŸ -DEPSãåç §ããããšã§ãä»»æã®ãšãã«ãããã©ã®å€æŽãå€æŽããŸã
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useEffect(() => {
props.dispatch(searchMediaAction("rain"));
}, []);
@luojinghui ïŒlintãšã©ãŒã解決ãããã©ããæããŠãã ãã
åããšã©ãŒ
åãåé¡ã componentDidMountã®åäœãæš¡å£ãããã èŠåã«ã¯èå³ããããŸããã äœããå€ãã£ããšãã«ããã¯ãåå®è¡ããããªã
useEffect()
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å Žåããã®èŠåã衚瀺ããªãããšãææ¡ããŸãããã®å Žåãéçºè
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ã±ãŒã¹2ã§ã¯ãåºæ¬çã«ReactHookã®ããã¥ã¡ã³ãä»æ§ã«åŸã£ãŠcomponentDidMountã€ãã³ãããªãã¹ã³ããŠããŸãã lintãšã©ãŒã¯ãReactHookã®ããã¥ã¡ã³ãããã³éçºè ã®æåŸ ãšäžèŽããŠããŸããã
ãªããããééãããŠããã®ã§ããïŒ
解決çã¯ãããŸããïŒ
@kennylbj
ããŸããŸãªææ¡ãè©ŠããåŸããããæçµçã«ç§ã«ãšã£ãŠããŸããã£ãããšã§ãã åå¿è ã®ããã«ã³ãŒããæ¯èŒçåçŽã«ä¿ã€ããã«åªããªãããeslint-disableã䜿çšããªãããšã奜ã¿ãŸããã ãã®ã¢ãããŒãã«ãããuseCallbackå ã§ãã£ã¹ãããé¢æ°ãåŒã³åºããã«ãã£ã¹ãããé¢æ°ãæž¡ãããšãã§ããŸãã ã圹ã«ç«ãŠãã°ã
`` `javascript
// ...é¢æ°ã³ã³ããŒãã³ãå
const {dispatchFunc} = customHookïŒïŒ;
const memoizeDispatchFunc = useCallbackïŒdispatchFuncã[]ïŒ;
useEffectïŒïŒïŒ=> {
memoizeDispatchFuncïŒïŒ;
}ã[memoizeDispatchFunc]ïŒ;
ãã
空ã®é åãåé€ã§ããŸããïŒ ããããããšã¯ããŸãããããã§ãïŒã³ãŒãã¯ãŸã æåŸ ã©ããã«å®è¡ãããèŠåã¯æ¶ããŸãïŒãããã®ããã«ãã¹ãã§ã¯ãªãçç±ããããã©ããã¯ããããŸããã
useEffect(()=>{
myFunc();
}
)
@robthedevGreateãœãªã¥ãŒã·ã§ã³ã
reduxã䜿çšãããšãã³ãŒããåçŽåããããšãã§ããŸãã
const dispatch = useDispatch();
// redux can guarantee that the dispatch function will not change between renders.
// so we don't need to wrap it with useCallback for now.
useEffect(() => {
dispatch(actions());
}, [dispatch]);
ãã³ã®ãã®èšäºã¯ç§ã倧ãã«å©ããŠãããŸãã
ãã®åé¡ã®è§£æ±ºçã¯ãäŸåé¢ä¿ãåé€ããããšã§ã¯ãããŸããã代ããã«ãã³ã³ããŒãã³ãã®å€éšã§å°éå ·ãç¶æ ãå¿ èŠãšããªãé¢æ°ãæã¡äžããããå®çŸ©ãããŠããuseCallbackã«ã©ããããããšãã§ããŸãã
@kennylbj
ããŸããŸãªææ¡ãè©ŠããåŸããããæçµçã«ç§ã«ãšã£ãŠããŸããã£ãããšã§ãã åå¿è ã®ããã«ã³ãŒããæ¯èŒçåçŽã«ä¿ã€ããã«åªããªãããeslint-disableã䜿çšããªãããšã奜ã¿ãŸããã ãã®ã¢ãããŒãã«ãããuseCallbackå ã§ãã£ã¹ãããé¢æ°ãåŒã³åºããã«ãã£ã¹ãããé¢æ°ãæž¡ãããšãã§ããŸãã ã圹ã«ç«ãŠãã°ã
// ... inside function component const { dispatchFunc } = customHook(); const memoizeDispatchFunc = useCallback(dispatchFunc, []); useEffect(() => { memoizeDispatchFunc(); }, [memoizeDispatchFunc]);
ç§ã®å Žåãäžèšã®äŸã¯æ©èœããŸããã
ãã®ãšã©ãŒãååŸããŸãïŒ
TypeError: Cannot destructure property 'dispatchFunc' of 'componentDidMount(...)' as it is undefined.
@ react-teamïŒããããŒãã€ã©ãŒãã¬ãŒãã³ãŒãã :)è«ççã§ãããäžåºŠèªã¿ãããããããšã¯ã§ããŸãã...ã€ãã³ãã¯ç°¡åã«äœ¿çšã§ããå¿ èŠããããŸã...é¢æ°ãåŒã³åºãããã ãã«5è¡ä»¥äžã®ããžãã¯ãèšè¿°ããå¿ èŠã¯ãããŸããã
ç§ã®å Žåããšã©ãŒã¯æ¬¡ã®ç¶æ³ã§çºçããŸããã
useEffect(() => {
props.getTasks()
}, [])
ç§ã¯ããã次ã®ããã«ä¿®æ£ããŸããïŒ
const { getTasks } = props
useEffect(() => {
getTasks()
}, [getTasks])
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ããããšåãåé¡ã«çŽé¢ããReactéçºããŒã ãã¹ã¬ãããéããŠå
šå¡ãç¡èŠããå ŽåïŒ
ç§ã®åé¡ã¯ãã®ã¹ã¬ããã®ä»ã®åé¡ãšã¯ç°ãªã£ãŠããã®ã§ãä»ã®è²§ããéããŠãµã®ã®ç©Žã«èœã¡ãå Žåã«åããŠå ±æããŸãç§ã¯ã¡ããã©1æéåããŠã³ããŠããŸã
function hydrate( _state, _errors=false) {
console.log('hydrate()');
setState({...state,..._state});
if(_errors){
setErrors({...errors,..._errors});
}
}
ãŠãŒã¶ãŒã¯ã次ã®ããã«ç¶æ
ã調æŽããããã«ããããuseEffect()
ã§äœ¿çšããå¿
èŠããããŸãã
useEffect(()=>{
hydrate({
name:'Garrett',
email:'[email protected]',
newsletter: 'yes'
});
},[hydrate]); //unfortunately, this causes an infinite render, because hydrate will always change
ã ããããã解決ããããã«ãç§ã¯ãã€ãã¬ãŒãé¢æ°ãuseCallback()
ã§ã©ããããããã«å€æŽããŸãããä»ã§ã¯ãã¹ãŠã®ã¬ã³ããªã³ã°ã§å€æŽãããŠããŸããïŒç§ã¯æšæž¬ããŸãïŒããããŠããããããã¯ããã©ãŒãã³ã¹ã«ãšã£ãŠããè¯ãã§ãããããæ¬åœãªãç§ã¯ã«ã¹ã¿ã ããã¯ããè¿ããããã¹ãŠã®ãã«ããŒé¢æ°ã«ãããå®è£
ããŸãã
const hydrate = useCallback(( _state, _errors=false )=> {
console.log('hydrate()');
setState({...state,..._state});
if(_errors){
setErrors({...errors,..._errors});
}
},[]);
誰ãããããæ¬åœãã©ããã確èªã§ããŸããïŒ useCallback
ã¯ã¬ã³ããªã³ã°ã§hydrate
ãå€æŽãããã®ãé²ãã§ããã®ã§ãããã©ãŒãã³ã¹ãåäžãããããã«ãã®ãããªãã¹ãŠã®é¢æ°ãuseCallback
ã§ã©ããããæ¹ãããããè¯ãã§ãããïŒ
redux can guarantee that the dispatch function will not change between renders.
ããããã§ããïŒ
ãããããèšã£ãŠããããã¥ã¡ã³ããžã®ãªã³ã¯ããé¡ãããŸãã
詳现ã«ã€ããŠã¯https://overreacted.io/a-complete-guide-to-useeffect/#decouple-updates-from-actionsã確èªããããå®è£ ã®è©³çŽ°ã«ã€ããŠã¯useEffectãœãŒã¹ã³ãŒãã確èªããŠãã ããã
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çãã¯ãReactã¯ããã£ã¹ãããé¢æ°ãã³ã³ããŒãã³ãã®åç¶æéãéããŠäžå®ã§ããããšãä¿èšŒãããšããããšã§ãã ãããã£ãŠãäžèšã®äŸã§ã¯ãééãåãµãã¹ã¯ã©ã€ãããå¿ èŠã¯ãããŸããã
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äœå人ãã®éçºè ããããšåãåé¡ã«çŽé¢ããReactéçºããŒã ãã¹ã¬ãããéããŠå šå¡ãç¡èŠããå ŽåïŒ
ã»ãŒããã ããã§ç§ã¯ããã¯ãè©ŠããŠã¿ãŸãããããã®èŠåã衚瀺ãããŸããããããã¯æå³ããªããå ¬åŒããã¥ã¡ã³ãã®ãããã«ãå«ãŸããŠããŸããã ããã®ãšãã§ã¯ãã1åã ãå®è¡ããŠãã ããããªã©ã®åºæ¬çãªãŠãŒã¹ã±ãŒã¹ã§ããã»ã©å€ãã®åé¡ãçºçããå Žåãããã¯ãæ¬æ Œçãªäœæ¥ã®æºåãã§ããŠãããã©ããæ¬åœã«çåã«æããŸãã
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åãåé¡ã«çŽé¢ããŠããŸãïŒ
解決ã
ïŒããã¯ç§ã®ããã«åããïŒïŒ
const onInit = function(){
console.log('initiated', Date.now());
}
useEffect(onInit, []);
ãªã³ãã£ã³ã°åŽã§åé¡ãä¿®æ£ãããã®ã§ãããã¡ãã£ãš...
@ ra30rçŽ æŽãããåé¿çã§ãããå¯äœçšãçºçããå¯èœæ§ããããã©ããçåã«æã£ãŠããŸããïŒ ïŒèãïŒ
ãŸã äœããããŸãããïŒ ð
Udemyã®ã³ãŒã¹ãããã©ãŒã æ€èšŒãšã©ãŒãããªã¬ãŒããããšãåŠãã ã±ãŒã¹ããããŸããã
ããã«ãããäŸåé¢ä¿ã®æ¬ èœããããã£ã¹ãããããããªã¬ãŒãããŸããããããã§ãæ©èœããŸããã
useEffect(() => {
if (state.business_name.value) {
const delay = setTimeout(() => dispatch({ type: "businessNameAfterDelay" }), 1000)
return () => clearTimeout(delay)
}
}, [state.business_name.value])
@ ra30rã®äŸã䜿çšããŠããšã©ãŒãã¯ãªã¢ããããã«ããã«å€æŽããŸããã
const businessNameAfterDelay = function () {
if (state.business_name.value) {
const delay = setTimeout(() => dispatch({ type: "businessNameAfterDelay" }), 1000)
return () => clearTimeout(delay)
}
}
useEffect(businessNameAfterDelay, [state.business_name.value])
ãªããããééãããŠããã®ã§ããïŒ
ç§ã¯çããã©ããã«äžãããããšä¿¡ããŠããŸã..ç¬..ãšã«ãã..解決çã¯æ¬¡ã®ããã«ããããšã§ãïŒ
useEffect(() => {
dispatch();
}, [dispatch]);
ã圹ã«ç«ãŠãã°ïŒïŒ
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ç§ã¯çããã©ããã«äžãããããšä¿¡ããŠããŸã..ç¬..ãšã«ãã..解決çã¯æ¬¡ã®ããã«ããããšã§ãïŒ
useEffect(() => { dispatch(); }, [dispatch]);
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ã¯ãããã®åé¿çã¯æ©èœããŸãã @ kennylbjã¯å°ãåã«ããã§èšããŸããã
ãªãåé¡ã¯è§£æ±ºãããã®ã§ããïŒ ããã«ãããã«ã€ããŠã®ããŒã ããããŸã... xd
ç§ã®åé¡ã¯ãã®ãããªãã®ã§ãïŒãµã³ãã«ã³ãŒãïŒïŒ
const [userStatus, setUserStatus]: any = React.useState([]);
const [userData, setUserData]: any = React.useState([]);
useEffect(() => {
setUserStatus(!userStatus);
return () => {};
}, [userData]);
ãããã£ãŠãã³ãŒãã®ããã«ã userData
å€æŽããã£ããšãã«userStatus
å€ãå€æŽããŸãããã®å Žåã userStatus
å€ã確èªããå Žåã¯ããããdepsã«è¿œå ããŸãã
const [userStatus, setUserStatus]: any = React.useState([]);
const [userData, setUserData]: any = React.useState([]);
useEffect(() => {
setUserStatus(!userStatus);
return () => {};
}, [userData, userStatus]);
ãã®ã·ããªãªã§ã¯ãç¡éã«ãŒãã«ãªããŸã
@spmsupun
useStateã®ã³ãŒã«ããã¯ã¹ã¿ã€ã«ã䜿çšããŠãuseEffectã®äŸåé¢ä¿é
åã«userStatuså€æ°ãå°å
¥ãããªãããã«ããããšãã§ããŸãã
useEffect(() => {
setUserStatus(prevState => !prevState);
return () => {};
}, [userData]);
ãããŠãããã¯ããããæ©èœæŽæ°ã§ãã
解決ç->äŸåé¢ä¿ã®ããã«æåŸã«ãã£ã¹ããããè¿œå ããã ã
React Hook useEffectã«ã¯ãäŸåé¢ä¿ããããŸããïŒ 'dispatch'ãuseEffect(() => { axios.get('http://localhost:8000/api/future-registrations') .then((result) => { dispatch(initRegistrationsAction(result.data)); }); ** }, [dispatch]);**
@kennylbjããã¯ã1ã€ã®ç¶æ ãæ±ãå Žåã«é©ããŠããŸããç§ã®å®éã®ã·ããªãªã¯ãå°éå ·ã䜿çšããå Žåã§ãã 芪ããå°éå ·ãéä¿¡ããŠããŸããã2åå€æŽããããããusereffectã¯2ååŒã³åºããŸããããã®äžã§ãªã¹ããŒãå®è¡ããŠãããšã2åãªãã¹ã³ããŸãã
@spmsupunããããäŸåé¢ä¿é åã®å€æ°ãå€æŽããããã³ã«ãåã®ãªã¹ããŒã®ç»é²ã解é€ããŠæ°ãããªã¹ããŒãç»é²ããã®ã¯ããæ®éã®ããšã ãšæããŸãïŒããšãã°ãpropsã®userIdãå€æŽãããå Žåããªã¹ããŒãå€æŽããå¿ èŠããããŸããïŒã ãããŠããã®æ¯ãèãã¯ãreactãæåŸ ãããã®ã§ãã
ããã§ããªã¹ããŒã2ååŒã³åºãããããªãå Žåã¯ãæž¡ãããå°éå ·ã«ãã£ãšæ³šæãæããã¬ã³ããªã³ã°äžã«å€æŽãããªãããã«ããå¿ èŠããããšæããŸãã
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次ã®ç¶æ³ãçºçããå Žåãããã¯çºçããªããšæããŸãã
ts
// call useEffect if and only if sockeId changed.
useEffect(() => {
const unregister = register(socketId);
return () => unregister(socketId);
}, [socketId])
ç°ãªãã¬ã³ããªã³ã°äžã«å€æŽãããäŸåé¢ä¿é åã®ä»ã®å€æ°ãããããã®åäœãåŒãèµ·ãããŸããïŒ
ãã3ã€ã®äŸåé¢ä¿ã§ãããç§ã¯ãããããã€ãã®ç°ãªãæ¹æ³ã§ç解ããŠããŸã
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èŠåã¡ãã»ãŒãžã§ç€ºåãããŠããããã«ãããªãã¯ãã®ããã«ããããšãã§ããŸã
const initFetch = useCallback(() => { dispatch(fetchPosts()); }, [dispatch]); useEffect(() => { initFetch(); }, [initFetch]);
ãããŒãéåžžæè°¢äœ ð
ð以äžã®ã³ãŒãã¹ããããã¯ç§ã«ãšã£ãŠæ¬åœã«ããŸãæ©èœããŸã
ã³ã³ããŒãã³ãã«ããŠã³ãããŸãã
const onInit = () => getUsers()
useEffect(onInit, [])
ãã©ã¡ãŒã¿å€æŽæ
const onInit = () => getUser(id)
useEffect(onInit, [id])
æåã®åé¿çïŒreact-hooks / exhaustive-depsïŒ "off"
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ã³ã³ããŒãã³ãã«ããŠã³ãããŸãã
const onInit = () => getUsers() useEffect(onInit, [])
ãã©ã¡ãŒã¿å€æŽæ
const onInit = () => getUser(id) useEffect(onInit, [id])
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ç§ã¯ãreactããã¥ã¡ã³ãã@luojinghuiã®ãŠãŒã¹ã±ãŒã¹ãå®å šã«ã«ããŒããŠãããšã¯æããŸããããããç§ãæã£ãŠãããã®ãšåãã§ãã
ç¹å®ã®é¢æ°ãåŒã³åºãæ¹æ³ã¯è€æ°ãããŸããã€ãŸãã setCenterPosition()
ã§ãã ç¶æ
ã®å€åïŒ useEffect
ãä»ããŠæ¥ç¶ïŒãã¯ãªãã¯ãã³ãã©ãŒïŒçŽæ¥åŒã³åºãããïŒãªã©ãç£èŠããããšã§åŒã³åºãããšãã§ããŸãã
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ããããéåžžãå®éã®äŸã§ã¯ãã¯ã©ã¹ã³ã³ããŒãã³ãïŒ this.setCenterPosition(...)
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èŠããããããã¯ãå®éã«æ©èœãã£ã±ãã«é©ããŠãããã©ããçåã«æãå§ããŠããŸããè€éãªã³ã³ããŒãã³ãã
å®éã«ã¯ããããŸãããããããã解決çã¯useCallback
const setCenterPosition = useCallback(() => {
...
}, [Stage, elePositionArr, setElePositionArr]);
useEffect() => {
...
}, [stageRef, Stage, currentIndex, setCenterPosition]);
...ããããããã¯ç§ã«ã¯ã¡ãã£ãšã²ã©ãã§ãããããŠç§ã¯ãã£ãšããããªæ¹æ³ãããããšãæãã§ããŸãã ãã¶ã@gaearonã¯ç¢ºèªã§ããŸããïŒ
åãåé¡ã«çŽé¢ããŠããç§ã¯useEffect
// eslint-disable-next-line react-hooks/exhaustive-deps
ã®çµããã«ãã®è¡ã䜿çšããŠèŠåbuãç¡å¹ã«ããããšãã§ããŸãããç§ã¯ããã䜿ããããããŸãã
ãããç§ã®ã³ãŒãã§ã
`const [itemsãsetItems] = useStateïŒ[
{{
ååïŒããã¹ã1ãã
idïŒ1
}ã
{{
ååïŒããã¹ã2ãã
idïŒ2
}ã
{{
ååïŒããã¹ã3ãã
idïŒ3
}ã
{{
ååïŒããã¹ã4ãã
idïŒ4
}ã
{{
ååïŒããã¹ã5ãã
idïŒ5
}
]ïŒ;
useEffectïŒïŒïŒ=> {
const intervalId = setIntervalïŒïŒïŒ=> {
setItemsïŒshuffleArrayïŒitemsïŒïŒ;
}ã1000ïŒ;
returnïŒïŒ=> {
clearIntervalïŒintervalIdïŒ;
};
// eslint-disable-next-line react-hooks / exhaustive-deps
}ã[]ïŒ;
ãã®åé¡ã«å¯Ÿããç§ã®è§£æ±ºçã¯ããããã®å Žåã«Reactããã¯ã®äœ¿çšãåã«åæ¢ããããšã§ããã ã³ã³ããŒãã³ãã«componentDidMount
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èŠãªå Žåã¯ãã¯ã©ã¹ã³ã³ããŒãã³ãã䜿çšããã ãã§ãé çã®çš®ãæžããããšãã§ããŸãã ã¯ã©ã¹ã³ã³ããŒãã³ãã¯å®å
šã«åé¡ãããŸããããã®ã¹ã¬ããã§äœãã蚌æãããå Žåãè€éãªç¶æ
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èŠãªå ŽåãReact Hooksã¯ããããå®å
šã«çœ®ãæããæºåãã§ããŠããŸããïŒãããã®ã»ãšãã©ã®å Žåãå©ç¹ãããããããšããããŸãã-ããªãã®ã³ãŒãã¯_æ¬åœã«_ã§ãReact Hooksã䜿çšããæ¹ãã¯ããã«åªããŠããŸããïŒïŒ
ç§èªèº«ã®ReactHooksã®äœ¿çšããããŒã«ãã©ã°ãªã©ãèšå®ããããã®useState
ãããªåçŽãªãã®ã«å¶éããŸãã ã³ã³ããŒãã³ããè€éã«ãªãã useEffect
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èŠã«ãªã£ãå Žåã¯ãã¯ã©ã¹ã³ã³ããŒãã³ãã®æ¹ãé©ããŠããå¯èœæ§ãããããšã瀺ãå
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ïŒããããããããããã«ç·šéïŒã
ããã¯ä»ã®ãšããç§ã®è§£æ±ºçã§ãïŒ
const mounted = () => {
dispatch(something());
}
useEffect(mounted, []);
ããããšã@ ra30r react / issues / 15865ïŒissuecomment-651254164
æãåèã«ãªãã³ã¡ã³ã
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