I am trying to return the value from function that has the onSnapshot() event but keep getting this weird error. Basically, I call this action and return the data from it like I would in any other function. But I keep getting this error and I do not know how to fix it.
This is the error
Uncaught TypeError: Cannot add property 0, object is not extensible
at Array.push (<anonymous>)
This the function
export const getQuestions = () => {
var questions = [];
onSnapshot(collection(firebaseDatabase, "questions"), (querySnapshot) => {
querySnapshot.docs.forEach((doc) => {
if (doc.data() !== null) {
questions.push(doc.data());
}
});
});
return questions;
};
Also this function is used with Redux Thunk and Redux Toolkit.
import { createSlice, createAsyncThunk } from "@reduxjs/toolkit";
import { getQuestions } from "../../utils/firebase-functions/firebase-functions";
export const getAllQuestions = createAsyncThunk(
"allQuestions/getAllQuestions",
async () => {
const response = getQuestions();
return response;
}
);
export const allQuestionsSlice = createSlice({
name: "allQuestions",
initialState: {
allQuestions: [],
loading: false,
error: null,
},
extraReducers: {
[getAllQuestions.pending]: (state) => {
state.loading = true;
state.error = null;
},
[getAllQuestions.fulfilled]: (state, action) => {
state.allQuestions = action.payload;
state.loading = false;
state.error = null;
},
[getAllQuestions.rejected]: (state, action) => {
state.loading = false;
state.error = action.payload;
},
},
});
export default allQuestionsSlice.reducer;
Where it is dispatched
const dispatch = useDispatch();
const tabContentData = useSelector(
(state) => state.allQuestions.allQuestions
);
useEffect(() => {
dispatch(getAllQuestions());
}, [dispatch]);
console.log(tabContentData);
You can try returning a promise when the data is being fetch for first time as shown below:
let dataFetched = false;
export const getQuestions = () => {
return new Promise((resolve, reject) => {
onSnapshot(collection(firebaseDatabase, "questions"), (querySnapshot) => {
querySnapshot.docs.forEach((doc) => {
if (doc.data() !== null) {
questions.push(doc.data());
}
});
if (!dataFetched) {
// data was fetched first time, return all questions
const questions = querySnapshot.docs.map(q => ({ id: q.id, ...q.data()}))
resolve(questions)
dataFetched = true;
} else {
// Questions already fetched,
// TODO: Update state with updates received
}
});
})
};
getQuestions() now returns a Promise so add an await here:
const response = await getQuestions();
For updates received later, you'll have to update them directly in your state.