I am creating a survey questionnaire form with reusable React components for the page layout with state coming from my Redux store. My state has updated, but the updated state is not rendering properly on the page. Specifically on the review route, my item.value
are missing. How can I get values to render?
App.jsx
import React, { useEffect, useState } from 'react';
import axios from 'axios';
import './App.css';
import { useDispatch, useSelector } from 'react-redux';
import { Route, useHistory } from 'react-router-dom';
function App() {
const history = useHistory();
const dispatch = useDispatch();
const feedbackSchema = useSelector((store) => store.feedbackSchema);
const [inputValue, setInputValue] = useState('');
useEffect(() => {
fetchFeedback();
}, []);
const fetchFeedback = () => {
axios({
method: 'GET',
url: 'api/feedback',
})
.then((response) => {
dispatch({
type: 'SET_FEEDBACK',
payload: response.data,
});
})
.catch((error) => {
console.log('You had a axios GET error', error);
});
};
const handleSubmit = (item, index) => {
console.log(item, inputValue);
dispatch({
type: 'SET_VALUE',
payload: [item, inputValue],
});
history.push(
feedbackSchema[index + 1]?.route
? `/${feedbackSchema[index + 1]?.route}`
: '/review'
);
};
return (
<div className="App">
<header className="App-header">
<h1 className="App-title">Feedback!</h1>
<h4>Don't forget it!</h4>
</header>
{feedbackSchema.map((item, index) => {
return (
<div key={item.key} className="feedback-container">
<Route exact path={`/${item.route}`}>
<h1>{item.header}</h1>
<form>
<div className="feedback-input">
<p className="feedback-topic">{item.topic}</p>
<input
type="text"
value={inputValue}
onChange={(event) => setInputValue(event.target.value)}
/>
<br />
<button
type="button"
onClick={() => handleSubmit(item.key, index)}
>
Next
</button>
</div>
</form>
</Route>
</div>
);
})}
<Route exact path={`/review`}>
<h1>Review Your Feedback</h1>
{feedbackSchema.map((feedback) => {
return (
<p key={feedback.key}>
{JSON.stringify(feedback)}
{feedback.key}: {feedback.value}
</p>
);
})}
</Route>
</div>
);
}
export default App;
Store.js
import { applyMiddleware, combineReducers, createStore } from "redux";
import logger from "redux-logger";
const feedbackList = (state = [], action) => {
if (action.type === 'SET_FEEDBACK') {
return action.payload;
}
return state;
}
const feedbackSchema = (
state = [
{ key: "feeling", route: "", header: "How are you feeling today?", topic: "Feeling?", value: "" },
{ key: "understanding", route: "understanding", header: "How well are you understanding the content?", topic: "Understanding?", value: "" },
{ key: "support", route: "support", header: "How well are you being supported?", topic: "Support?", value: "" },
{ key: "comments", route: "comments", header: "Any comments you want to leave?", topic: "Comments", value: "" }
],
action
) => {
if (action.type === 'SET_VALUE') {
state.map((feedback) => {
if (feedback.key === action.payload[0]) {
feedback.value = action.payload[1]
}
return feedback;
})
}
return state;
}
const store = createStore(
combineReducers({
feedbackList,
feedbackSchema,
}),
applyMiddleware(logger)
)
export default store;
index.jsx
import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';
import App from './components/App/App';
import { Provider } from 'react-redux';
import { HashRouter as Router } from 'react-router-dom';
import store from './store';
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
<React.StrictMode>
<Provider store={store}>
<Router>
<App />
</Router>
</Provider>
</React.StrictMode>
);
2
Answers
The state is updated but the UI is not updating because
react-redux
checks if the data is changed by comparing the address of the data.In your
Store.js
fileYou are returning same data by updating the state. Hence the reducer compares if address of state is equal to address of state. This makes it think no changes are made.
Instead you can do this,
By returning a new variable
temp
reducer will understand the changes are made and UI will be updated.Issue
You are mutating state and not returning new state references.
React works by using shallow reference equality checks and if the
state
is the same reference as the previous render cycle React won’t necessarily trigger a component rerender.Solution Suggestions
To address this correctly all state, and nested state, that is being updated necessarily needs to be a new object reference.
I suggest the following re-write:
It is more conventional to use
switch
statements in reducer functions though, so it could also be re-written to a more standard pattern/form: