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Redux action doesn't dispatch after page refresh

I have an issue with redux and probably useEffect(I am not sure where my mistake is). I am trying to get information from PokeAPI and store information in the redux state. The problem is that the information about pokemons don't include pokemon types(fire, water, etc.), to solve this I am sending requests to fetch those types from a different endpoint and I want to include these types of specific pokemon to redux state.
1-redux state without types of pokemons
2-redux state with types of pokemons
My goal is to have a state like in the second picture with types. But when I refresh the page, I only acquire the first picture(actions aren't dispatching). When I change something in my code and save it, I get types as well. I suspect that my problem is in the useEffect, but I couldn't find a solution without creating some nasty loops.
Note: Page parameter in fetchData coming from PokeAPI, it basically returns 15 pokemon for every page.(For now I am just experimenting on the first page)
This is my first question in stackoverflow, I already searched for similar questions but those were dealing with different aspects, so I decided to ask myself.
PokemonList.js --> this is where I need those types
import React, { useEffect } from 'react';
import { ListGroup, ListGroupItem } from "react-bootstrap";
import { useDispatch, useSelector } from 'react-redux';
import _ from "lodash";
import { GetPokemonList, GetSpecificPokemon } from '../redux/actions/PokemonAction';
import { Button } from 'react-bootstrap';
const PokemonList = () => {
const dispatch = useDispatch();
const pokemonList = useSelector(state => state.PokemonList);
useEffect(() => {
const fetchData = (page = 1) => {
dispatch(GetPokemonList(page));
}
fetchData();
}, [dispatch]);
useEffect(() => {
const fetchTypes = () => {
pokemonList.data.forEach(pokemon => {
dispatch(GetSpecificPokemon(pokemon.name));
});
}
fetchTypes();
}, [dispatch]);
const showData = () => {
if (!_.isEmpty(pokemonList.data)) {
return (
<div className="pokemon-list-wrapper">
{pokemonList.data.map((pokemon, index) => {
return (
<div className="pokemon-list-element" key={index}>
<ListGroup>
<ListGroupItem action href={`/pokemon/${pokemon.name}`} variant="success">{pokemon.name}
<Button style={{ float: "right" }}>Test</Button>
</ListGroupItem>
</ListGroup>
</div>
)
})}
</div>
)
}
if (pokemonList.loading) {
return <p>Loading...</p>
}
if (pokemonList.errorMessage !== "") {
return <p>{pokemonList.errorMessage}</p>
}
};
return (
<div>
{showData()}
</div>
)
};
export default PokemonList;
PokemonAction.js
import axios from "axios"
export const GetPokemonList = (page) => async (dispatch) => {
try {
dispatch({
type: "POKEMON_LIST_LOADING"
});
const perPage = 15;
const offset = (page * perPage) - perPage;
const res = await axios.get(`https://pokeapi.co/api/v2/pokemon?limit=${perPage}&offset=${offset}`);
dispatch({
type: "POKEMON_LIST_SUCCESS",
payload: res.data
});
} catch (e) {
dispatch({
type: "POKEMON_LIST_FAIL"
});
}
}
export const GetSpecificPokemon = (name) => async (dispatch) => {
try {
const res = await axios.get(`https://pokeapi.co/api/v2/pokemon/${name}`);
dispatch({
type: "SPECIFIC_POKEMON_SUCCESS",
payload: res.data
});
} catch (e) {
dispatch({
type: "SPECIFIC_POKEMON_FAIL"
});
}
}
PokemonListReducer.js
const initialState = {
data: [],
loading: false,
errorMessage: "",
count: 0
};
const PokemonListReducer = (state = initialState, action) => {
switch (action.type) {
case "POKEMON_LIST_LOADING":
return {
...state,
loading: true,
errorMessage: ""
};
case "POKEMON_LIST_FAIL":
return {
...state,
loading: false,
errorMessage: "unable to get pokemon"
};
case "POKEMON_LIST_SUCCESS":
return {
...state,
loading: false,
data: action.payload.results,
errorMessage: "",
count: action.payload.count
};
case "SPECIFIC_POKEMON_SUCCESS":
const typesMap = action.payload.types.map((type) => {
return type.type.name;
})
return {
...state,
data: state.data.map((pokemon) => pokemon.name === action.payload.name
? {...pokemon, types: typesMap}
: pokemon
),
loading: false,
errorMessage: ""
}
case "SPECIFIC_POKEMON_FAIL":
return {
...state,
loading: false,
errorMessage: "unable to get pokemon"
};
default:
return state
}
}
export default PokemonListReducer;

This is happening because your second useEffect does not wait for your first useEffect to finish and because of that the pokemon list is empty. On code change, since the state already has the pokemon list pre-filled, the second useEffect finds the list and does it's thing. You have to guarantee that the second action is caller right after the first one in order for this to work properly. One way to do this is to dispatch the GetSpecificPokemon action for each pokemon before finishing the GetPokemonList action. Something like this should work:
export const GetPokemonList = (page) => async (dispatch) => {
try {
dispatch({
type: "POKEMON_LIST_LOADING"
});
const perPage = 15;
const offset = (page * perPage) - perPage;
const res = await axios.get(`https://pokeapi.co/api/v2/pokemon?limit=${perPage}&offset=${offset}`);
dispatch({
type: "POKEMON_LIST_SUCCESS",
payload: res.data
});
res.data.result.forEach(pokemon => {
dispatch(GetSpecificPokemon(pokemon.name));
});
} catch (e) {
dispatch({
type: "POKEMON_LIST_FAIL"
});
}
}
Note that you won't be needing the second useEffect if you are doing this. You might also have to change displaying/not displaying the loader part yourself.
Another way is to add pokemonList as the second object in the useEffect's array parameter. I haven't tested it yet but this should work. For example:
useEffect(() => {
const fetchTypes = () => {
pokemonList.data.forEach(pokemon => {
dispatch(GetSpecificPokemon(pokemon.name));
});
}
fetchTypes();
}, [dispatch, pokemonList]);
This will call the useEffect whenever there is a change in pokemonList. In your implementation, useEffect is only called once since the value of dispatch never really changes after that. Adding pokemonList to the array results in the useEffect being called when there is a change in pokemonList also. Use this approach if you want the GetPokemonList action to always be separate from GetSpecificPokemon action i.e there are cases when both are not called together. If both are always called together then the first approach is cleaner.
That being said, these implementations actually result in a lot of network calls. The best way is to avoid the second call if possible (change your UI accordingly?) since you do not have any control over the API. If you do have control over the API you could include the extra data in the first request's response.
Edit: Here is the batch logic
const p = pokemonList.map(({ name }) =>
axios.get(`https://pokeapi.co/api/v2/pokemon/${name}`)
);
const res = await Promise.all(p);
const data = res.map((r) => ({
...r.data,
types: r.data.types.map((type) => type.type.name) // the logic you were using for types
}));
dispatch({
type: "SPECIFIC_POKEMON_SUCCESS",
payload: data
});
And then update the state in the reducer like
case "SPECIFIC_POKEMON_SUCCESS":
return {
...state,
data: action.payload,
loading: false,
errorMessage: ""
};

Update State Provider from Function

I have this periodic useEffect hook:
const [state, dispatch] = useContext(NTTrackerContext);
useEffect(() => {
const interval = setInterval(() => {
dispatch({type: "REFRESH_APIS"}); // function that I'd like to use to update
console.log(state.raceapi.racedata)
}, 60000);
return () => clearInterval(interval);
}, [])
So, I have made a context provider, and I'd like to update it through the dispatch function. I want to use dispatch because I've written most of my code this way, but if there are better methods, please comment or add an answer.
In case you are wondering, yes, the function above is wrapped in NTTrackerContextProvider, code as provided below.
Context:
export const NTTrackerContext = React.createContext([{}]);
const initialState = {
user: {username: "", authenticated: false, email: "",},
raceapi: {
racedata: {'data': null}, racerlog: {}, racerdata: {}, teamdata: {},
}
};
const nttrackerReducer = (state, action) => {
switch (action.type) {
case 'LOGGED_IN': { // example of how I've written some parts of my reducer
let {user, raceapi, ...etc} = state;
let {userdata} = action;
return {
...etc, user: {...user, ...userdata,}, raceapi: {...raceapi},
}
}
default: return state;
}
};
const NTTrackerContextProvider = props => {
const initState = props.initState || initialState;
const [state, dispatch] = useReducer(nttrackerReducer, initState);
return (
<NTTrackerContext.Provider value={[state, dispatch]}>
{props.children}
</NTTrackerContext.Provider>
);
};
export default NTTrackerContextProvider;
The APIs that I want to refresh is stored in the raceapi object. racedata, racerlog, etc. all have their own individual URLs; for instance, http://127.0.0.1:8000/data/racedata_json/ for racedata.
I have my initial values fetched using fetch("http://127.0.0.1:8000/data/racedata_json/"), by this point, but I can't find a way to update the state using a function in my body functional component.
Can anyone please help? Thanks in advance.

Redux useSelect doesn't get updated as expected

I’m working on a little proof of concept project, using React and Redux, and useSelector and useDispatch hooks. I’m trying to fetch some data asynchronously and I use thunks for that. I think I'm conceptually missing something. Even though my state works as expected, I can not get my data from api using useSelector.
Here is the code. My action:
import axios from "axios";
export const API_FETCH_POSTS = 'API_FETCH_POSTS';
export const fetchPosts = (postId) => { // to simulate post request
return (dispatch) => {
let baseUrl = 'https://jsonplaceholder.typicode.com/';
let postFix = 'comments?postId=';
let url = `${baseUrl}${postFix}${postId}`;
axios.get(url)
.then(response => {
const data = response.data;
console.log(JSON.stringify(data)); // work!
dispatch(fetchPostsSuccess(data));
});
}
};
const fetchPostsSuccess = posts => {
return {
type: API_FETCH_POSTS,
payload: posts
}
};
My reducer:
import {API_FETCH_POSTS} from "./apiActions";
const initialState = {
getPostsReq : {
posts: [],
}
};
const apiReducer = (state = initialState, action) => {
let getPostsReq;
switch (action.type) {
case API_FETCH_POSTS:
getPostsReq = {
posts: [...state.getPostsReq.posts]
};
return {
...state,
getPostsReq
};
default: return state;
}
};
export default apiReducer;
And rootReducer:
import {combineReducers} from 'redux';
import apiReducer from "./api/apiReducer";
export default combineReducers({
api: apiReducer
})
And store:
const initialState = {};
const store = createStore(
rootReducer,
initialState,
composeWithDevTools(
applyMiddleware(thunk)
)
);
export default store;
I have a problem with my React component:
function PostContainer(props) {
const posts = useSelector(state => state.api.getPostsReq.posts);
const dispatch = useDispatch();
const logPosts = () => {
{/*why doesn't this line work???*/}
console.log(JSON.stringify(posts));
}
return (
<div>
<button onClick={() => {
dispatch(fetchPosts(1));
logPosts();
}}>Fetch Posts</button>
<div>
{/*why doesn't this line work???*/}
{posts.map(post => <p>{post.body}</p>)}
</div>
</div>
);
}
export default PostContainer;
I expect that after I press the button, the function fetchPosts gets dispatched and because I use thunk I shouldn’t have any problems with asynchronicity. But by some reason I can’t get my state, using useSelector() hook. I can neither render the state, nor log it in the console.
What am I missing here?
Here is the whole code if it is more convenient - https://github.com/JavavaJ/use-select-problem

Problem: Not Storing Posts
Your selector is fine, it's your reducer that's the problem! You dispatch an action which has an array of posts in the payload:
const fetchPostsSuccess = posts => {
return {
type: API_FETCH_POSTS,
payload: posts
}
};
But when you respond to this action in the reducer, you completely ignore the payload and instead just return the same posts that you already had:
const apiReducer = (state = initialState, action) => {
let getPostsReq;
switch (action.type) {
case API_FETCH_POSTS:
getPostsReq = {
posts: [...state.getPostsReq.posts]
};
return {
...state,
getPostsReq
};
default: return state;
}
};
Solution: Add Posts from Action
You can rewrite your reducer like this to append the posts using Redux immutable update patterns.
const apiReducer = (state = initialState, action) => {
switch (action.type) {
case API_FETCH_POSTS:
return {
...state,
getPostsReq: {
...state.getPostsReq,
posts: [...state.getPostsReq.posts, ...action.payload]
}
};
default:
return state;
}
};
It's a lot easier if you use Redux Toolkit! With the toolkit you can "mutate" the draft state in your reducers, so we don't need to copy everything.
const apiReducer = createReducer(initialState, {
[API_FETCH_POSTS]: (state, action) => {
// use ... to push individual items separately
state.getPostsReq.posts.push(...action.payload);
}
});

Async redux action to fetch data is causing component to reload and cause react to react max depth in reload

I am trying to create a component that allows detecting changes in the redux store. Once the shouldUpdateData flag is set in the store, the component responsible for updating should fetch the data by using an async action creator. In my case, either the error "Maximum updates have reached" occurs or the update never happens.
Depending on the dispatch function stopFetching() (turns off the shouldUpdateData flag), the error or outcome changes. If I do the dispatch inside the action creator there are endless updates. If the code is used as it is below, no update occurs.
The reason I used the useSelector() hook from 'react-redux' is to detect a change in the store for the loading attribute.
Thank you in advance.
Here is the action creator:
export function updateDataAsync(id) {
return function (dispatch) {
// dispatch(fetchDataRequest());
return fetch(`/api/user/${id}/data`, {
method: "GET",
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
}
})
.then(res => res.json())
.then(
(result) => {
let {projects, notes} = result;
// New data and dispatch function
dispatch(fetchDataSuccess({projects, notes}));
},
(error) => { dispatch(fetchDataFailure(error)) }
)
}
}
Here is the reducer for this action creator:
export function savedData(state = DATA_INITIAL_STATE, action) {
switch(action.type) {
case FETCH_STATES.FETCH_DATA_REQUEST:
return {
...state,
loading: true
}
case FETCH_STATES.FETCH_DATA_SUCCESS:
return {
loading: false,
data: action.data,
error: ''
}
case FETCH_STATES.FETCH_DATA_FAILURE:
return {
loading: false,
data: {},
error: action.error.message
}
default:
return state;
}
}
The React component that is doing the update:
function StoreUpdater({ update, userId, shouldUpdate, startFetch, stopFetch, children }) {
const loading = useSelector(state => state.savedData.loading);
let reqSent = useRef(false);
useEffect(()=>{
if(!reqSent && shouldUpdate) {
startFetch();
update(userId)
reqSent.context = true;
}
})
return loading ? <LoadingAnimation /> : children;
}
const mapStateToProps = (state) => {
return {
userId: state.user.id,
shouldUpdate: state.shouldUpdateData // The flag that should trigger the update
}
}
const mapDispatchToProps = (dispatch) => {
return {
stopFetch: () => { dispatch(setShouldFetchData(false)) },
update: (id) => { dispatch(updateDataAsync(id)) },
startFetch: () => dispatch(fetchDataRequest()),
}
}
export default connect(mapStateToProps, mapDispatchToProps)(StoreUpdater);

You dint pass any dependency to useEffect so it will be called on every render which is causing infinite renders
change useEffect to
useEffect(()=>{
if(!reqSent && shouldUpdate) {
startFetch();
update(userId)
reqSent.context = true;
}
},[])
For complete information regarding useEffect refer this link

The reference I created inside the component responsible of the updates, was causing the problem. The reference was preventing the update dispatch to occur due to the if statement being false.

mapStateToProps and mapDispatchToProps were react-redux higher order functions to connect classes components into the store. there equalants at functional components are useSelector and useDispatch. re-write your HOC redux adaption into hooks, and add [ dependency ] at useEffect usage
function StoreUpdater({ update, userId, shouldUpdate, startFetch, stopFetch, children }) {
const loading = useSelector(state => state.savedData.loading);
const userId = useSelector(state => state.user.id);
const shouldUpdate = useSelector(state => state.shouldUpdateData);
let reqSent = useRef(false);
const dispatch = useDispatch() // import from 'react-redux'
useEffect(()=>{
if(!reqSent && shouldUpdate) {
dispatch(startFetch());
dispatch(update(userId));
reqSent.context = true;
}
}, [reqSent, shouldUpdate, startFetch, dispatch, update, userId])
return loading ? <LoadingAnimation /> : children;
}
export default StoreUpdater ;

Unable to read state updated by useReducer hook in context provider

I am using useReducer hook to manage my state, but it seems like I have a problem with reading updated state in my context provider.
My context provider is responsible to fetch some remote data and update the state based on responses:
import React, { useEffect } from 'react';
import useAppState from './useAppState';
export const AppContext = React.createContext();
const AppContextProvider = props => {
const [state, dispatch] = useAppState();
const initialFunction = () => {
fetch('/some_path')
.then(res => {
dispatch({ type: 'UPDATE_STATE', res });
});
};
const otherFunction = () => {
fetch('/other_path')
.then(res => {
// why is `state.stateUpdated` here still 'false'????
dispatch({ type: 'DO_SOMETHING_ELSE', res });
});
}
};
const actions = { initialFunction, otherFunction };
useEffect(() => {
initialFunction();
setInterval(otherFunction, 30000);
}, []);
return (
<AppContext.Provider value={{ state, actions }}>
{props.children}
</AppContext.Provider>
)
};
export default AppContextProvider;
and useAppState.js is very simple as:
import { useReducer } from 'react';
const useAppState = () => {
const reducer = (state, action) => {
switch (action.type) {
case 'UPDATE_STATE':
return {
...state,
stateUpdated: true,
};
case 'DO_SOMETHING_ELSE':
return {
...state,
// whatever else
};
default:
throw new Error();
}
};
const initialState = { stateUpdated: false };
return useReducer(reducer, initialState);
};
export default useAppState;
The question is, as stated in the comment above, why is state.stateUpdated in context provider's otherFunction still false and how could I access state with latest changes in the same function?

state will never change in that function
The reason state will never change in that function is that state is only updated on re-render. Therefore, if you want to access state you have two options:
useRef to see a future value of state (you'll have to modify your reducer to make this work)
const updatedState = useRef(initialState);
const reducer = (state, action) => {
let result;
// Do your switch but don't return, just modify result
updatedState.current = result;
return result;
};
return [...useReducer(reducer, initialState), updatedState];
You could reset your setInterval after every state change so that it would see the most up-to-date state. However, this means that your interval could get interrupted a lot.
const otherFunction = useCallback(() => {
fetch('/other_path')
.then(res => {
// why is `state.stateUpdated` here still 'false'????
dispatch({ type: 'DO_SOMETHING_ELSE', res });
});
}
}, [state.stateUpdated]);
useEffect(() => {
const id = setInterval(otherFunction, 30000);
return () => clearInterval(id);
}, [otherFunction]);