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Unable to access Reducer & state values

I am unable to access my state values saved in store on any screen. values reach to actions but when I access it from store it returns always undefined.
Every thing is in separate files
Reducer 1
import * as Actions from '../actionTypes'
import initialStore from './initialStore'
const homeModuleReducer = (state = initialStore, action) => {
switch (action.type) {
case Actions.SET_PROFILE_ONE:
console.log('call here')
return {
...state,
currentUser: action.profile
}
default:
return state;
}
}
export default homeModuleReducer
Reducer 2
import * as Actions from '../actionTypes'
import initialStore from './initialStore'
const loginModuleReducer = (state = initialStore, action) => {
switch (action.type) {
case Actions.SET_PROFILE:
return {
...state,
currentUser: action.profile
}
case Actions.SET_INITIAL_LOADING_STATUS:
return {
...state,
isInitialLoadingDone: action.loadingStatus
}
default:
return state;
}
}
export default loginModuleReducer
Combine Reducer
import { combineReducers } from 'redux'
import homeModuleReducer from './homeModuleReducer'
import loginModuleReducer from './loginModuleReducer'
export default combineReducers({
homeModuleReducer,
loginModuleReducer,
})
Store
import { createStore, applyMiddleware } from 'redux'
import thunkMiddleware from 'redux-thunk';
import rootReducer from './reducers'
let store = createStore(rootReducer, applyMiddleware(thunkMiddleware));
export default store;
usage:
const mapStateToProps = (state) => ({
stateLoaded: state.rootReducer.isInitialLoadingDone,
profile: state.rootReducer.currentUser
});
Error:
undefined is not an object (evaluating 'state.rootReducer.isInitialLoadingDone')

You already combined your reducers so you can access reducer by it's key like this :
const mapStateToProps = (state) => ({
stateLoaded: state.homeModuleReducer.isInitialLoadingDone, // here homeModuleReducer is just an example. Change with reducer key in which isInitialLoadingDone is belong
profile: state.loginModuleReducer.currentUser
});

With hooks its much easier
wrap your root with store
import {Provider} from 'react-redux';
const App = () => {
return (
<Provider store={store}>
<Yourcomponent/>
</Provider>
);
};
export default App;
Access your state in any component like this
import { useSelector } from "react-redux";
const state = useSelector(state => state)

Redux: useSelector value is undefined despite it appearing in devTools

I'm trying to setup a redux environment and I'm stumped as to why I am having this behavior.
I have my root state here on my reducer:
export type RootState = {
counter: number;
};
const initialState: RootState = { counter: 0 };
const staticLesson = (state = initialState, action: any) => {
switch (action.type) {
case "INCREMENT":
return state.counter + 1;
default:
return state;
}
};
export default staticLesson;
I then combine it here:
import staticLesson from "./staticLesson/index";
import { combineReducers } from "redux";
const rootReducer = combineReducers({
staticLesson,
});
export default rootReducer;
I wrap my App with the Provider:
import { createStore } from "redux";
import rootReducer from "./redux/reducers";
import { Provider } from "react-redux";
import { composeWithDevTools } from "redux-devtools-extension";
const store = createStore(rootReducer, composeWithDevTools());
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.getElementById("root")
);
Yet, when I try to log it in my component, the value is undefined.
const Component = () => {
const staticLesson = useSelector((state: RootState) => state);
const dispatch = useDispatch();
console.log("counter", staticLesson.counter); <-- logs undefined
return (
...
)
}
What I don't understand is why if I just log staticLesson, it appears as expected in my console. But if I try to access the value on the object, instead of getting the value 0 for my counter ... I get undefined. staticLesson is showing up in my devTools, it's there ... I'm stumped, what am i messing up?

I'm pretty sure you should be returning the staticLesson property from the state in your useSelector call. In useSelector you're returning the entire state. So it should be:
const staticLesson = useSelector((state: RootState) => state.staticLesson);

TypeError: Object is not iterable (cannot read property Symbol(Symbol.iterator))

I tried running this code, but it's giving me a runtime error saying
TypeError: Object is not iterable (cannot read property
Symbol(Symbol.iterator))
here is the code.
import React, { useContext} from "react";
import { GlobalContext } from '../GlobalState';
const MediaCard = ({ songs, categotyTitle }) => {
const [{}, dispatch] = useContext(GlobalContext);
const setCurrentVideoSnippet = data => {
dispatch({ type: "setCurrentVideoSnippet", snippet: data });
};
export default MediaCard;
the error is pointing at this line of code const [{}, dispatch] = useContext(GlobalContext);
the GlobalState code
import React, { useReducer } from "react";
export const GlobalContext = React.createContext();
const initialState = {
currentVideoSnippet: {},
};
const reducer = (state, action) => {
switch (action.type) {
case "setCurrentVideoSnippet":
return {
...state,
currentVideoSnippet: action.snippet
};
default:
return state;
}
};
export const GlobalState = props => {
const globalState = useReducer(reducer, initialState);
return (
<GlobalContext.Provider value={globalState}>
{props.children}
</GlobalContext.Provider>
);
};

I know this doesn't solve the OP's issue, but for those like me who wound up on this page with the same run time error message, my issue was caused because of the way I was importing the GlobalContext component.
Wrong Way:
import GlobalContext from '../GlobalState';
Correct Way:
import { GlobalContext } from '../GlobalState';
This fixed the issue I was running into with the same error message.

It looks like you forgot to wrap your component with provider you created as you currently use it:
<GlobalState>
<MediaCard />
</GlobalState>

Below is my code, it is just an example to show you why the error is occurring in your code.
The data layer you created is not been wrapped around the components of the whole web app therefore it's not able to be recognized by the MediaCard component... what you need to do is just go in your index.js and wrap the StateProvider around the main app
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';
import reducer, { initialState } from "./reducer";
import { StateProvider} from'./StateProvider';
ReactDOM.render(
<React.StrictMode>
<StateProvider initialState={ initialState } reducer={ reducer }>
<App />
</StateProvider>
</React.StrictMode>,
document.getElementById('root')
);

react-redux TypeError: notes.map is not a function

Why am I getting TypeError: notes.map is not a function in the following part of my Notes component? {notes.map((note) => (
components/Notes.js
import React, { Component } from "react"
import { connect } from "react-redux"
const mapStateToProps = (state) => {
return { notes: state.notes }
}
const NotesList = ({ notes }) => (
<ul className="notes_list">
{notes.map((note) => (
<li className="note_body" key={note.id}>
<div dangerouslySetInnerHTML={{ __html: note.body }}></div>
</li>
))}
</ul>
)
const Notes = connect(mapStateToProps)(NotesList);
export default Notes;
reducers/notes.js
import * as types from '../actions/actionTypes'
const initialState = {
notes: [{id: 1, body: "hey"}]
}
function notes(state = initialState, action) {
switch (action.type) {
...
default:
return state
}
}
export default notes
root reducer
import { combineReducers } from 'redux'
import notes from './notes'
import noteForm from './noteForm'
const rootReducer = combineReducers({
notes,
noteForm
})
export default rootReducer
app.js
import React, { Component } from 'react';
import Notes from './components/Notes'
import NoteForm from './components/NoteForm'
const App = () => (
<div className="App">
<NoteForm />
<Notes />
</div>
)
export default App
---upd
store
import { createStore, applyMiddleware } from 'redux'
import rootReducer from '../reducers'
import {ping} from './enhancers/ping'
import thunk from 'redux-thunk'
export default function configureStore(initialState) {
const store = createStore(rootReducer, initialState, applyMiddleware(thunk, ping))
return store
}
index.js
...
import configureStore from './store/configureStore'
const store = configureStore()
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.getElementById('root'));

Are you providing the connect function with a store? If so, everything looks fine to me -- it'd be useful to see your store initialization code.
Create a store with createStore from redux and wrap your App with a Provider from react-redux:
app.js
...
import notesReducer from './reducers/notes'
import { createStore } from 'redux'
const store = createStore(notesReducer) // use combineReducers when you add a 2nd reducer
const App = () => (
<Provider store={store}>
<div className="App">
<NoteForm />
<Notes />
</div>
</Provider>
)
If you already have a Provider somewhere else, check if everything's okay there.
Here's my fully working example - I copied your Notes.js file and wrote up the following App.js - no errors whatsoever (I bundled store creation and reducers all in one file for simplicity):
import React, { Component } from 'react';
import { Provider } from 'react-redux'
import { createStore } from 'redux'
import Notes from './Notes'
const initialState = {
notes: [{
id: 1,
body: 'testing'
}]
}
function notes(state = initialState, action) {
switch (action.type) {
default:
return state
}
}
const store = createStore(notes)
export default () => (
<Provider store={store}>
<Notes />
</Provider>
)
Update for combineReducers
When using combineReducers, your reducers' initialState will already be namespaced in the store under the key which was used in the combineReducers call. Change your notes reducer's initialState to an array:
import * as types from '../actions/actionTypes'
// no need for { notes: [] } here, combineReducers({ notes }) will take care of that
const initialState = [{ id: 1, body: 'hey' }]
function notes(state = initialState, action) {
switch (action.type) {
...
default:
return state
}
}
export default notes

When you get map isn't a function that means you're not calling the data correctly.
I see in notes reducer page you're not calling the states correctly
function notes(state = initialState, action) {
switch (action.type) {
...
default:
return state
}
}
Change it to:
function notes(state = initialState.notes, action) {
switch (action.type) {
...
default:
return state
}
}
The regular way to do this is to not putting your states in an array
const initialState = {
id: 1,
body: "hey"
}
function notes(state = initialState, action) {
switch (action.type) {
...
default:
return state
}
}
This will works fine

since my root reducer has the following structure
const rootReducer = combineReducers({
notes
})
I can reach notes by state.notes.notes
const mapStateToProps = (state) => {
return { notes: state.notes.notes }
}
having the following initial state structure for notes
const initialState = {
notes: []
}

Cannot read state from Redux store. What did I miss?

Here is my index.js where I initially dispatch an action to read my list of locations:
import 'babel-polyfill';
import React from 'react';
import { render } from 'react-dom';
import configureStore from './store/configureStore';
import {Provider} from 'react-redux';
import { Router, browserHistory } from 'react-router';
import routes from './routes';
import {loadLocationList} from './actions/locationActions';
import './css/styles.css';
const store = configureStore();
render(
<Provider store={store}>
<Router history={browserHistory} routes={routes} />
</Provider>,
document.getElementById('app')
);
Then here is my action where I get the data & then create an action out of it:
export function loadLocationListSuccess(alistingData) {
return { type: types.LOAD_LOCATION_LIST_SUCCESS, listingData: alistingData};
}
export function loadLocationList() {
return function(dispatch){ //we return a function that accepts a parameter, we just called it dispatch
//dispatch(fetchCallActions.fetchCallStart("")); // we dispatch a function fetchCallStart to indicate the start of our call, this is to keep in check with our asynchronous function calls
let link = 'http://example.com:8399/location';//our fetch url
console.log(link); //we log our link, just for debug purposes
return fetch(link) //start fetch
.then(function(response) {
return response.json();
}).then(function(json) {
dispatch(loadLocationListSuccess(json));
}).catch(function(ex) {
console.log('parsing failed', ex);
});
};
}
Then here is my reducer:
import * as types from '../actions/actionTypes';
export default function locationReducer(state = [], action) {
switch(action.type) {
case types.LOAD_LOCATION_LIST_SUCCESS:
return {listingData: action.listingData};
default:
return state;
}
}
Then here is my mapStateToProps & connect function:
function mapStateToProps(state, ownProps) {
return {
// we'll call this in our component -> this.props.listingData
listingData: state.listingData
};
}
export default connect(mapStateToProps, mapDispatchToProps)(homePage);
For some reason, it cannot read state.listingData or am I actually doing it wrongly? Anyone can help me with this problem?
I tried logging state.listingData and it showed undefined
Here is my configureStore:
import {createStore, applyMiddleware} from 'redux';
import rootReducer from '../reducers';
import reduxImmutableStateInvariant from 'redux-immutable-state-invariant';
import thunk from 'redux-thunk';
export default function configureStore(initialState) {
return createStore(
rootReducer,
initialState,
applyMiddleware(thunk, reduxImmutableStateInvariant())
);
}
Here is my combined Reducer:
import {combineReducers} from 'redux';
import courses from './courseReducer';
import locations from './locationReducer';
const rootReducer = combineReducers({
courses,
locations
});
export default rootReducer;
Did I not connect it to the store properly?
Recent update:
Logging JSON.stringify(state) in mapStateToProps would actually shows the result. Thanks guys.
The correct path turned out to be state.locations.listingData because I think in my combined Reducer I included the reducer as locations so maybe thats why the state for it is state.locations. Hope this helps anyone with the problem.

Can you show the code of configureStore file? The problem might be there, may be you forgot to add reducer to list of reducers.
Does the action works right? Did you log data before dispatch(loadLocationListSuccess(json));?
UPD:
Because of rootReducer. Each reducer creates their own key in store. When you combine your reducers in rootReducer, like:
import locations from './locationReducer';
const rootReducer = combineReducers({
courses,
locations
});
It creates store with this kind of structure:
const store = {
courses: {},
locations: {}
}
So, after that you dispatched action and reducer changed the data to this:
const store = {
courses: {},
locations: {
listingData: someData
}
}
If you want to access to listingData like: state.listingData, you need to change a little your reducer and combineReducer to:
export default function listingData(state = {}, action) {
switch(action.type) {
case types.LOAD_LOCATION_LIST_SUCCESS:
return action.listingData;
default:
return state;
}
}
...
import listingData from './locationReducer';
const rootReducer = combineReducers({
courses,
listingData
});