I can see my array in state, but I don't know why elements of array doesn't display on the app interface.
const [members, setMembers] = useState([])
useEffect( () => {
getMembers();
}, [props.event])
const getMembers = () => {
let new_members = [];
console.log(props.event)
props.event && props.event.uczestnicy.map(member => {
member.get().then(doc => {
let new_member;
new_member = {
...doc.data(),
id: doc.id
}
new_members.push(new_member)
})
setMembers(new_members)
})
console.log(new_members)
console.log(members)
}
[...]
{members && members.map(member => {
console.log('mem',member)
return(
<div key={member.id}>
{member.nick}
</div>
)
})}
So I can see this array in Components using React Developer Tools, but even console.log doesn't see it in the moment of performing.
And console.log(new_members) and console.log(members) result :
Your member values are fetch asynchronously, so its ideal if you set state only after all the values are resolved. For this you can use a Promise.all
const getMembers = async () => {
let new_members = [];
console.log(props.event)
if(props.event) {
const val = await Promise.all(props.event.uczestnicy.map(member => {
return member.get().then(doc => {
let new_member;
new_member = {
...doc.data(),
id: doc.id
}
return new_member
})
});
setMembers(values);
console.log(values);
}
}
Related
Trying to wrap my head around what the process would be to change an image source depending on the value of what is returned from the database.
Snippet:
function KnifesComponent() {
const knifeCollection = collection(db, "knives");
const [knives, setKnives] = useState([]);
useEffect(() => {
onSnapshot(knifeCollection, (snapshot) => {
setKnives(snapshot.docs.map((doc) => ({ ...doc.data(), id: doc.id })));
});
}, []);
return (
{knives.map((skin) => {
return (
{skin.rarity} // Returns "Ultra" for Example
<div><img src={isUltra : require('../../public/Rarity_Ultra.png')}></div>
);
}
I was thinking of making a const with all the values in and then using as needed but not sure how exactly to approach it
const rarities = {
Exclusive: require('../../public/Rarity_Exclusive.png'),
Ultra: require('../../public/Rarity_Ultra.png'),
}
What is the proper way to conditionally format different images based on values?
You can change the rarities object to this (paths as values):
const rarities = {
Exclusive: '../../public/Rarity_Exclusive.png',
Ultra: '../../public/Rarity_Ultra.png',
}
Then you can then access the image from the object by rarity.
function KnifesComponent() {
const knifeCollection = collection(db, "knives");
const [knives, setKnives] = useState([]);
useEffect(() => {
onSnapshot(knifeCollection, (snapshot) => {
setKnives(snapshot.docs.map((doc) => ({ ...doc.data(), id: doc.id })));
});
}, []);
return (
{
knives.map((skin) => {
return (
{skin.rarity} // Returns "Ultra" for Example
<div>
<img src={require(rarities[skin.rarity])}>
</div>
);
})
}
);
}
The object also can be like this (just the image names):
const rarities = {
Exclusive: 'Rarity_Exclusive.png',
Ultra: 'Rarity_Ultra.png',
}
And access them:
<img src={require(`../../public/${rarities[skin.rarity]}`)}>
I am building a messaging feature using socket.io and react context;
I created a context to hold the conversations that are initially loaded from the server as the user passes authentication.
export const ConversationsContext = createContext();
export const ConversationsContextProvider = ({ children }) => {
const { user } = useUser();
const [conversations, setConversations] = useState([]);
const { socket } = useContext(MessagesSocketContext);
useEffect(() => {
console.log(conversations);
}, [conversations]);
useEffect(() => {
if (!socket) return;
socket.on("userConversations", (uc) => {
let ucc = uc.map((c) => ({
...c,
participant: c.participants.filter((p) => p._id != user._id)[0],
}));
setConversations([...ucc]);
});
socket.on("receive-message", (message) => {
console.log([...conversations]);
console.log(message);
setConversations((convs) => {
let convIndex = convs.findIndex(
(c) => c._id === message.conversation._id
);
let conv = convs[convIndex];
convs.splice(convIndex, 1);
conv.messages.unshift(message);
return [conv, ...convs];
});
});
}, [socket]);
return (
<ConversationsContext.Provider
value={{
conversations,
setConversations,
}}
>
{children}
</ConversationsContext.Provider>
);
};
The conversations state is updated with the values that come from the server, and I have confirmed that on the first render, the values are indeed there.
Whenever i am geting a message, when the socket.on("receive-message", ...) function is called, the conversations state always return as []. When checking devTools if that is the case I see the values present, meaning the the socket.on is not updated with the conversations state.
I would appreciate any advice on this as I`m dealing with this for the past 3 days.
Thanks.
You can take "receive-message" function outside of the useEffect hook and use thr reference as so:
const onReceiveMessageRef = useRef();
onReceiveMessageRef.current = (message) => {
console.log([...conversations]);
console.log(message);
setConversations((convs) => {
let convIndex = convs.findIndex(
(c) => c._id === message.conversation._id
);
let conv = convs[convIndex];
convs.splice(convIndex, 1);
conv.messages.unshift(message);
return [conv, ...convs];
});
};
useEffect(() => {
if (!socket) return;
socket.on("userConversations", (uc) => {
let ucc = uc.map((c) => ({
...c,
participant: c.participants.filter((p) => p._id != user._id)[0],
}));
setConversations([...ucc]);
});
socket.on("receive-message", (...r) => onReceiveMessageRef.current(...r));
}, [socket]);
let me know if this solves your problem
i am woking on weather api and storing perticular data in an array arr but value is not available in arr. also state arrdata is null too.
i tried to not use state but still not getting data in arr . it show reading undefined value.
export default function App() {
const [cityName, setCityName] = useState("delhi");
const [arrData, setArrData] = useState(null);
const getWeatherInfo = async () => {
const url = "https://api.openweathermap.org/data/2.5/forecast";
const api = "4beffc863037e89f0f181d893d1cf79b";
fetch(`${url}?q=${cityName}&units=metric&appid=${api}`)
.then((res) => res.json())
.then((getData) => {
if(getData.list[4].main !== null){
const arr = [];
for (let i = 0; i <= 40; i++) {
if (i % 8 === 0) {
arr.push({
temprature: getData.list[i].main.temp,
Min_temp: getData.list[i].main.temp_min,
Max_temp: getData.list[i].main.temp_max,
date: getData.list[i].dt_txt,
mood: getData.list[i].weather[0].main,
weathermoodIcon: getData.list[i].weather[0].icon,
Humidity: getData.list[i].main.humidity,
});
}}
setArrData(arr);
}});
};
useEffect(() => {
getWeatherInfo()
}, []);
console.log(arrData)
const onInputChange = (e) => {
setCityName(e.target.value);
};
const onSubmitCity = () => {
getWeatherInfo();
};
return (
<>
<Input onChangeValue={onInputChange} onSubmit={onSubmitCity} />
</>
);
}
This seems to be working. Please do not forget to use optional chaining
import {useState, useEffect } from 'react';
export default function App() {
const [cityName, setCityName] = useState("delhi");
const [arrData, setArrData] = useState(null);
const getWeatherInfo = async () => {
const url = "https://api.openweathermap.org/data/2.5/forecast";
const api = "4beffc863037e89f0f181d893d1cf79b";
fetch(`${url}?q=${cityName}&units=metric&appid=${api}`)
.then((res) => res.json())
.then((getData) => {
if(getData.list[40]?.main !== null){
const arr = [];
console.log(getData.list)
for (let i = 0; i <= 4; i++) {
if (i % 8 === 0) {
arr.push({
temprature: getData.list[i]?.main.temp,
Min_temp: getData.list[i]?.main.temp_min,
Max_temp: getData.list[i]?.main.temp_max,
date: getData.list[i]?.dt_txt,
mood: getData.list[i]?.weather[0].main,
weathermoodIcon: getData.list[i]?.weather[0].icon,
Humidity: getData.list[i]?.main.humidity,
});
}}
setArrData(arr);
}});
};
useEffect(() => {
getWeatherInfo();
}, []);
console.log(arrData)
const onInputChange = (e) => {
setCityName(e.target.value);
};
const onSubmitCity = () => {
getWeatherInfo();
};
return (
<>
<input onChange={onInputChange} onSubmit={onSubmitCity} />
<h1> {JSON.stringify(arrData)} </h1>
<button onClick = {onSubmitCity}> Submit </button>
</>
);
}
I have a small project, to fetch images from Unsplash, even ı check many times, I still have one problem with my code, I am running my code, but it always gives this error, but I don't get it. Any idea will be appreciated.
App.js:
function App() {
const [pins, setNewPins] = useState([])
const getImages = (term) => {
return unsplash.get ("https://api.unsplash.com/search" , {
params: {
query: term
}
});
};
const onSearchSubmit = (term) => {
getImages(term).then((res) => {
let results = res.data.results;
let newPins = [
...results,
...pins
]
newPins.sort(function(a,b) {
return 0.5 - Math.random();
});
setNewPins(newPins);
});
};
const getNewPins = () => {
let promises = [];
let pinData = [];
let pins = ['Istanbul','cats','sky','lake','nature']
pins.forEach((pinTerm) => {
promises.push (
getImages(pinTerm).then((res) => {
let results = res.data.results;
pinData = pinData.concat(results);
pinData.sort(function(a,b) {
return 0.5 - Math.random();
});
});
);
});
Promise.all(promises).then(()=> {
setNewPins(pinData);
});
};
useEffect(() => {
getNewPins();
}, []);
return (
<div className="app">
<Header onSubmit={onSearchSubmit}/>
<Mainboard pins={pins}/>
</div>
)}
export default App;
The getNewPins method is re-created everytime in your app after each render and you're using it inside an useEffect which is saying to place it inside the [] array. If you do so, it will later say to wrap getNewPins inside useCallback to prevent re-renders. Instead of that you can just place the whole function inside your useEffect like so (since it's a one time operation that's done initially) :-
function App() {
const [pins, setNewPins] = useState([])
const getImages = (term) => {
return unsplash.get ("https://api.unsplash.com/search" , {
params: {
query: term
}});
};
const onSearchSubmit = (term) => {
getImages(term).then((res) => {
let results = res.data.results;
let newPins = [
...results,
...pins,
]
newPins.sort(function(a,b){
return 0.5 - Math.random();
});
setNewPins(newPins);
});
};
useEffect(() => {
const getNewPins = () => {
let promises = [];
let pinData = [];
let pins = ['Istanbul','cats','sky','lake','nature']
pins.forEach((pinTerm) => {
promises.push (
getImages(pinTerm).then((res) => {
let results = res.data.results;
pinData = pinData.concat(results);
pinData.sort(function(a,b){
return 0.5 - Math.random();
});
})
);
});
Promise.all(promises).then(()=> {
setNewPins(pinData);
});
};
getNewPins();
}, []);
return (
<div className="app">
<Header onSubmit={onSearchSubmit}/>
<Mainboard pins={pins}/>
</div>
);
}
export default App;
I have an array of data object to be rendered. and this array of data is populated by Firestore onSnapshot function which i have declared in the React hook: useEffect. The idea is that the dom should get updated when new data is added to firestore, and should be modified when data is modified from the firestore db.
adding new data works fine, but the problem occurs when the data is modified.
here is my code below:
import React, {useState, useEffect} from 'react'
...
const DocList = ({firebase}) => {
const [docList, setDocList] = useState([]);
useEffect(() => {
const unSubListener = firebase.wxDocs()
.orderBy("TimeStamp", "asc")
.onSnapshot({
includeMetadataChanges: true
}, docsSnap => {
docsSnap.docChanges()
.forEach(docSnap => {
let source = docSnap.doc.metadata.fromCache ? 'local cache' : 'server';
if (docSnap.type === 'added') {
setDocList(docList => [{
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()
}, ...docList]);
console.log('document added: ', docSnap.doc.data());
} // this works fine
if (docSnap.type === 'modified') {
console.log('try docList from Lists: ', docList); //this is where the problem is, this returns empty array, i don't know why
console.log('document modified: ', docSnap.doc.data()); //modified data returned
}
})
})
return () => {
unSubListener();
}
}, []);
apparently, i know the way i declared the useEffect with empty deps array is to make it run once, if i should include docList in the deps array the whole effect starts to run infinitely.
please, any way around it?
As commented, you could have used setDocList(current=>current.map(item=>..., here is working example with fake firebase:
const firebase = (() => {
const createId = ((id) => () => ++id)(0);
let data = [];
let listeners = [];
const dispatch = (event) =>
listeners.forEach((listener) => listener(event));
return {
listen: (fn) => {
listeners.push(fn);
return () => {
listeners = listeners.filter((l) => l !== fn);
};
},
add: (item) => {
const newItem = { ...item, id: createId() };
data = [...data, newItem];
dispatch({ type: 'add', doc: newItem });
},
edit: (id) => {
data = data.map((d) =>
d.id === id ? { ...d, count: d.count + 1 } : d
);
dispatch({
type: 'edit',
doc: data.find((d) => d.id === id),
});
},
};
})();
const Counter = React.memo(function Counter({ up, item }) {
return (
<button onClick={() => up(item.id)}>
{item.count}
</button>
);
});
function App() {
const [docList, setDocList] = React.useState([]);
React.useEffect(
() =>
firebase.listen(({ type, doc }) => {
if (type === 'add') {
setDocList((current) => [...current, doc]);
}
if (type === 'edit') {
setDocList((current) =>
current.map((item) =>
item.id === doc.id ? doc : item
)
);
}
}),
[]
);
const up = React.useCallback(
(id) => firebase.edit(id),
[]
);
return (
<div>
<button onClick={() => firebase.add({ count: 0 })}>
add
</button>
<div>
{docList.map((doc) => (
<Counter key={doc.id} up={up} item={doc} />
))}
</div>
</div>
);
}
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>
You can do setDocList(docList.map... but that makes docList a dependency of the effect: useEffect(function,[docList]) and the effect will run every time docList changes so you need to remove the listener and idd it every time.
In your code you did not add the dependency so docList was a stale closure. But the easiest way would be to do what I suggested and use callback for setDocList: setDocList(current=>current.map... so docList is not a dependency of the effect.
The comment:
I don't think setDocList, even with the the prevState function, is guaranteed to be up to date by the time you get into that if statement
Is simply not true, when you pass a callback to state setter the current state is passed to that callback.
Based on #BrettEast suggestion;
I know this isn't what you want to hear, but I would probably suggest using useReducer reactjs.org/docs/hooks-reference.html#usereducer, rather than useState for tracking an array of objects. It can make updating easier to track. As for your bug, I don't think setDocList, even with the the prevState function, is guaranteed to be up to date by the time you get into that if statement.
I use useReducer instead of useState and here is the working code:
import React, {useReducer, useEffect} from 'react'
import { withAuthorization } from '../../Session'
import DocDetailsCard from './Doc';
const initialState = [];
/**
* reducer declaration for useReducer
* #param {[*]} state the current use reducer state
* #param {{payload:*,type:'add'|'modify'|'remove'}} action defines the function to be performed and the data needed to execute such function in order to modify the state variable
*/
const reducer = (state, action) => {
switch (action.type) {
case 'add':
return [action.payload, ...state]
case 'modify':
const modIdx = state.findIndex((doc, idx) => {
if (doc.id === action.payload.id) {
console.log(`modified data found in idx: ${idx}, id: ${doc.id}`);
return true;
}
return false;
})
let newModState = state;
newModState.splice(modIdx,1,action.payload);
return [...newModState]
case 'remove':
const rmIdx = state.findIndex((doc, idx) => {
if (doc.id === action.payload.id) {
console.log(`data removed from idx: ${idx}, id: ${doc.id}, fullData: `,doc);
return true;
}
return false;
})
let newRmState = state;
newRmState.splice(rmIdx,1);
return [...newRmState]
default:
return [...state]
}
}
const DocList = ({firebase}) => {
const [state, dispatch] = useReducer(reducer, initialState)
useEffect(() => {
const unSubListener = firebase.wxDocs()
.orderBy("TimeStamp", "asc")
.onSnapshot({
includeMetadataChanges: true
}, docsSnap => {
docsSnap.docChanges()
.forEach(docSnap => {
let source = docSnap.doc.metadata.fromCache ? 'local cache' : 'server';
if (docSnap.type === 'added') {
dispatch({type:'add', payload:{
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()
}})
}
if (docSnap.type === 'modified') {
dispatch({type:'modify',payload:{
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()
}})
}
if (docSnap.type === 'removed'){
dispatch({type:'remove',payload:{
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()
}})
}
})
})
return () => {
unSubListener();
}
}, [firebase]);
return (
<div >
{
state.map(eachDoc => (
<DocDetailsCard key={eachDoc.id} details={eachDoc} />
))
}
</div>
)
}
const condition = authUser => !!authUser ;
export default React.memo(withAuthorization(condition)(DocList));
also according to #HMR, using the setState callback function:
here is the updated code which also worked if you're to use useState().
import React, { useState, useEffect} from 'react'
import { withAuthorization } from '../../Session'
import DocDetailsCard from './Doc';
const DocList = ({firebase}) => {
const [docList, setDocList ] = useState([]);
const classes = useStyles();
useEffect(() => {
const unSubListener = firebase.wxDocs()
.orderBy("TimeStamp", "asc")
.onSnapshot({
includeMetadataChanges: true
}, docsSnap => {
docsSnap.docChanges()
.forEach(docSnap => {
let source = docSnap.doc.metadata.fromCache ? 'local cache' : 'server';
if (docSnap.type === 'added') {
setDocList(current => [{
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()
}, ...current]);
console.log('document added: ', docSnap.doc.data());
}
if (docSnap.type === 'modified') {
setDocList(current => current.map(item => item.id === docSnap.doc.id ? {
source: source,
id: docSnap.doc.id,
...docSnap.doc.data()} : item )
)
}
if (docSnap.type === 'removed'){
setDocList(current => {
const rmIdx = current.findIndex((doc, idx) => {
if (doc.id === docSnap.doc.id) {
return true;
}
return false;
})
let newRmState = current;
newRmState.splice(rmIdx, 1);
return [...newRmState]
})
}
})
})
return () => {
unSubListener();
}
}, [firebase]);
return (
<div >
{
docList.map(eachDoc => (
<DocDetailsCard key={eachDoc.id} details={eachDoc} />
))
}
</div>
)
}
const condition = authUser => !!authUser ;
export default React.memo(withAuthorization(condition)(DocList));
Thanks hope this help whoever is experiencing similar problem.