Develop Reference

How do i access redux state from another react component?

I am developing a lottery statistics app that gets data from a csv loaded from an input then I was wanting to read this data to the redux store so I can use it across multiple components.
I have successfully saved the data to the redux store once I import the file and read it through Header.js and using an action, but I am not sure how to access this in other components like e.g. Main.js.
I feel like I am still confused on how react/redux all fits together. I'm sorry if this has been asked before but everything I looked up online I couldn't get to work.
// index.js
import React from "react";
import ReactDOM from "react-dom";
import { createStore, applyMiddleware } from "redux";
import { Provider } from "react-redux";
import thunk from "redux-thunk";
import reducers from "./reducers";
import App from "./components/App";
const store = createStore(reducers, applyMiddleware(thunk));
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.querySelector("#root")
);
// App.js
import React from "react";
import Header from "./Header";
import Main from "./Main";
const App = () => {
return (
<div>
<Header />
<Main />
<div className="numbers-for-draw"></div>
</div>
);
};
export default App;
// Header.js
import React from "react";
import { CSVReader } from "react-papaparse";
import { fetchData } from "../actions";
import { connect } from "react-redux";
class Header extends React.Component {
constructor(props) {
super(props);
this.fileInput = React.createRef();
}
handleReadCSV = data => {
this.props.fetchData(data);
console.log(this.props.data);
};
handleOnError = (err, file, inputElem, reason) => {
console.log(err);
};
handleImportOffer = () => {
this.fileInput.current.click();
console.log("Got to handleImportOffer");
};
render() {
return (
<header>
<CSVReader
onFileLoaded={this.handleReadCSV}
inputRef={this.fileInput}
style={{ display: "none" }}
onError={this.handleOnError}
/>
<button onClick={this.handleImportOffer}>Import</button>
</header>
);
}
}
//Map what is in the redux store (e.g. state) to props
const mapStateToProps = state => ({
data: state.data
});
export default connect(mapStateToProps, {
fetchData: fetchData
})(Header);
// Main.js
import React from "react";
import { fetchData } from "../actions";
import { connect } from "react-redux";
const Main = () => {
console.log("In main");
console.log(this.props.data); //Blows up here.
return <div>Main</div>;
};
//Map what is in the redux store (e.g. state) to props
const mapStateToProps = state => ({
data: state.data
});
export default connect(mapStateToProps, {
fetchData: fetchData
})(Main);
// actions/index.js
export const fetchData = data => dispatch => {
console.log("Action");
const lottoData = {
stringNumbers: [
"one",
"two",
"three",
...
],
allResults: [],
winningNumbers: [],
winningNumbersAsStrings: []
};
const localData = data.data;
localData.shift();
localData.forEach(line => {
const lineObject = {
draw: line[0],
drawDate: line[1],
ballOne: line[2],
ballTwo: line[3],
ballThree: line[4],
ballFour: line[5],
ballFive: line[6],
ballSix: line[7],
bonusBall: line[8],
bonusBall2: line[9],
powerBall: line[10]
};
lottoData.allResults.push(lineObject);
let nums = [];
nums.push(parseInt(line[2]));
nums.push(parseInt(line[3]));
nums.push(parseInt(line[4]));
nums.push(parseInt(line[5]));
nums.push(parseInt(line[6]));
nums.push(parseInt(line[7]));
nums.sort((a, b) => {
if (a < b) {
return -1;
} else if (a > b) {
return 1;
} else {
return 0;
}
});
lottoData.winningNumbers.push(nums);
lottoData.winningNumbersAsStrings.push(nums.toString());
});
dispatch({ type: "FETCH_DATA", payload: lottoData });
};
// lottoReducer.js
export default (state = {}, action) => {
switch (action.type) {
case "FETCH_DATA":
return action.payload;
default:
return state;
}
};
// reducers/index.js
import { combineReducers } from "redux";
import lottoReducer from "./lottoReducer";
export default combineReducers({
data: lottoReducer
});

I haven't tested your code, but it seems to me that the only problem is in your Main.js
While you use a function component and not a class, you shouldn't use this to access your props. The following should work as expected:
const Main = (props) => {
console.log("In main");
console.log(props.data);
return <div>Main</div>;
};
//Map what is in the redux store (e.g. state) to props
const mapStateToProps = state => ({
data: state.data
});
export default connect(mapStateToProps, {
fetchData: fetchData
})(Main);

In your main.js you used functional components so this.props doesn't work there. You must pass props to your component and console.log(props.data).

New Components in Application cannot connect to redux

I have created a small application and connected it to Redux. Unfortunately when creating new components and using the same exact code those new components cannot seem to connect to redux and get undefined when accessing it (using mapStateToProps).
I have tried to create new Components and connect them again to no avail. I'm kind of at loss as to why it isn't working especially since the rest of the application can connect and get the state properly
index.js:
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import { Provider } from 'react-redux'
import store from './store'
ReactDOM.render(
<Provider store={store} >
<App />
</Provider>
, document.getElementById('root'));
store.js:
const initialState = {
guessedTimezone: '',
timezone: '',
pseudo: '',
};
function rootReducer(state = initialState, action) {
console.log(action);
if (action.type === 'CHANGE_TIMEZONE') {
return Object.assign({}, state, {
timezone: action.timezone,
guessedTimezone: action.guessedTimezone
})
}
if (action.type === 'CHANGE_PSEUDO') {
return Object.assign({}, state, {
pseudo: action.pseudo,
token: action.token
})
}
return state;
}
export default rootReducer;
new Component not connecting:
import React, { Component } from 'react'
import { connect } from 'react-redux'
export class TestPseudo extends Component {
render() {
console.log(this.props.pseudo);
return (
<div>
{this.props.pseudo}
</div>
)
}
}
const mapStateToProps = state => {
return {
pseudo: state.pseudo
}
}
export default connect(mapStateToProps)(TestPseudo)
Here for example this.props.pseudo returns undefined when, if the connection happens, it should return the value if i understand it correctly and yet it shows undefined
EDIT:
App.js as per requested :
import React, { Component } from 'react'
import { connect } from 'react-redux'
import Homepage from './Components/Homepage';
import moment from 'moment';
import moment_timezone from 'moment-timezone';
import HeaderApp from './Components/HeaderApp';
import { TestPseudo } from './Components/TestPseudo';
export class App extends Component {
async componentDidMount() {
let tz = moment.tz.guess(true);
let date = moment(new Date()).local();
let timezone = date['_i'].toString().split('(')[1].split(')')[0];
this.props.dispatch({
type: 'CHANGE_TIMEZONE',
guessedTimezone: tz,
timezone: timezone
})
console.log(`Guessed timezone: ${tz} (${timezone})`);
}
_showHomepage() {
if (this.props.showHomepage && this.props.loaded) {
return (
<div style={styles.mainWindow}>
{/*<Homepage click={this._handleClick} />*/}
<TestPseudo />
</div>
)
}
}
_showHeader() {
return (
<div>
<HeaderApp />
</div>
)
}
render() {
return (
<div>
{this._showHeader()}
{this._showHomepage()}
</div>
)
}
}
const styles = {
mainWindow: {
height: '100vh',
width: '100vw'
}
}
const mapStateToProps = state => {
return {
guessedTimezone: state.guessedTimezone,
timezone: state.timezone,
};
};
export default connect(mapStateToProps)(App);
I call that new Component instead of my old Component. The homepage can connect but not the new one so i think it's not a problem of emplacement

I think its here
import { TestPseudo } from './Components/TestPseudo';
You are importing the non-connected component. Try this
import TestPseudo from './Components/TestPseudo';
For your understanding, exporting as default can be imported like so;
export default Component
import WhateverName from ....
Named export like const or in your case class;
export class Component
import { Component } from ...
So use brackets when Named, and skip brackets when default.

higher order component can't see props

I'm using react with react-native and redux. The error comes to the component from the redux store. After that, i received: Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.
What is wrong with this? why hoc can't see the props?
My component:
import React, { Component } from 'react';
import withHandleError from './withHandleError';
class SendScreen extends Component {
render() {
const { error } = this.props;
return (
<div> Test </div>
)
}
};
const mapStateToProps = ({ppm}) => ({
error: ppm.error
})
export default withHandleError(connect(mapStateToProps)(SendScreen));
And HoC:
import React, { Component } from 'react';
import { ErrorScreen } from '../../ErrorScreen';
import { View } from 'react-native';
export default Cmp => {
return class extends Component {
render() {
const {error, ...rest } = this.props;
console.log(error) //// undefined....
if (error) {
return <ErrorScreen />
}
return <Cmp { ...rest } />
}
}
}

The order is which you call the HOCs matters when you want to access props supplied by one in another. Re-ordering your connect and withHandleError HOC will work
import React, { Component } from 'react';
import withHandleError from './withHandleError';
class SendScreen extends Component {
render() {
const { error } = this.props;
return (
<div> Test </div>
)
}
};
const mapStateToProps = ({ppm}) => ({
error: ppm.error
})
export default connect(mapStateToProps)(withHandleError(SendScreen));

React Native ListView to FlatList Migration

So I started learning react-native from videos and they have used ListView but as the ListView will be deprecated soon and will be removed. I get to know that FlatList will be the proper replacement but being a beginner I am not able to migrate to Flatlist.
import React, { Component } from "react";
import { ListView } from 'react-native';
import { connect } from 'react-redux';
import ListItem from './ListItem';
class LibraryList extends Component {
componentWillMount() {
const ds = new ListView.DataSource({
rowHasChanged: (r1,r2) => r1 !==r2
});
this.dataSource =ds.cloneWithRows(this.props.libraries);
}
renderRow(library) {
return <ListItem library = { library } />;
}
render() {
return(
<ListView
dataSource = {this.dataSource}
renderRow = {this.renderRow}
/>
);
}
}
const mapStateToProps = state => {
return { libraries: state.libraries };
};
export default connect(mapStateToProps) (LibraryList);

Welcome to stackoverflow.
Migrating should be pretty straightforward, you don't need a dataSource anymore. You can pass your array of items directly to the Component.
import React, { Component } from "react";
import { FlatList } from 'react-native';
import { connect } from 'react-redux';
import ListItem from './ListItem';
class LibraryList extends Component {
renderRow({item}) {
return <ListItem library = { item } />;
}
render() {
return(
<FlatList
data = {this.props.libraries}
renderItem = {this.renderRow}
/>
);
}
}
const mapStateToProps = state => {
return { libraries: state.libraries };
};
export default connect(mapStateToProps) (LibraryList);
Header over to the documentation here to find out more.

Trouble using actions in react-redux presentational component

I'm new to redux and having trouble wrapping my head around presentational and container components.
Relevant stack:
react v0.14.8
react-native v0.24.1
redux v3.5.2
react-redux v4.4.5
The issue:
I have a login button component, which when rendered checks the login status and calls the onSuccessfulLogin action which updates the state with the user's Facebook credentials.
However, when trying to separate this into separate presentational/container components, I'm unable to call the onSuccessfulLogin action: Error: onSuccessfulLogin is not defined.
What am I doing wrong here? I'd imagine there's something simple that I'm not understanding with the relationship between the two components and the connect() function.
Presentational Component (Login.js)
import React, { PropTypes } from "react-native";
import FBLogin from "react-native-facebook-login";
import UserActions from "../users/UserActions";
class LoginPage extends React.Component {
render() {
const { userData, onSuccessfulLogin } = this.props;
return (
<FBLogin
permissions={["email","user_friends"]}
onLoginFound= { data => {
onSuccessfulLogin(data.credentials);
}}
/>
)
}
};
export default LoginPage;
Container Component (LoginContainer.js)
import { connect } from 'react-redux';
import LoginPage from "../login/LoginPage";
import UserActions from "../users/UserActions";
const mapDispatchToProps = (dispatch) => {
return {
onSuccessfulLogin: (userData) => {
dispatch(UserActions.userLoggedIn(userData))
}
}
}
const mapStateToProps = (state) => {
return {
userData: state.userData
}
}
const LoginContainer = connect(
mapStateToProps,
mapDispatchToProps
)(LoginPage);
export default LoginContainer;
Also, if I wanted to make the updated state.userData accessible to the LoginPage component, how would I do that? Any help is appreciated!
Solved! When using ES6 classes, you're required to call super(props) in a constructor method in order to access the container's properties in the connected presentational component:
class LoginPage extends React.Component {
constructor(props){
super(props);
}
render(){
// ...
}
}

Your container component is supposed to be a component and it must have a render function with the dumb/presentational components you want to render.
import { connect } from 'react-redux';
import LoginPage from "../login/LoginPage";
import UserActions from "../users/UserActions";
class LoginContainer extends React.Component {
constructor(props){
super(props);
}
render() {
return (
<LoginPage userData={this.props.userData}
onSuccessfulLogin={this.props.onSuccessfulLogin}
/>
)
}
};
const mapDispatchToProps = (dispatch) => {
return {
onSuccessfulLogin: (userData) => {
dispatch(UserActions.userLoggedIn(userData))
}
}
}
const mapStateToProps = (state) => {
return {
userData: state.userData
}
}
export default connect(
mapStateToProps,
mapDispatchToProps
)(LoginPage);