Develop Reference

Redux Thunk for simple async requests

I am building a simple app to retrieve some recipes from an API URL.
I am reading the documentation of Thunk to implement it but I cannot understand how to set the async get request.
What is strange is that if I console.log the action passed into the reducer it definitely retrieves the correct object (a list of recipes for shredded chicken).
When I pass the action onto the the reducer, instead, it throws the error:
"Unhandled Rejection (Error): Given action "FETCH_RECIPES", reducer "recipes" returned undefined. To ignore an action, you must explicitly return the previous state. If you want this reducer to hold no value, you can return null instead of undefined."
Is there any error in my action creator? is the API call properly done?
Store
import React from 'react';
import { render } from 'react-dom'
import { Provider } from 'react-redux'
import { createStore, applyMiddleware } from 'redux'
import SearchBar from './components/App';
import thunk from 'redux-thunk';
import 'bootstrap/dist/css/bootstrap.css';
import rootReducer from './reducers';
const store = createStore(rootReducer, applyMiddleware(thunk));
render(
<Provider store={store}>
<SearchBar />
</Provider>,
document.getElementById('root')
)
Component
import React, { Component } from 'react';
import { connect } from 'react-redux';
import './App.css';
import { Button } from 'reactstrap';
import { Form } from 'reactstrap';
import { bindActionCreators } from 'redux';
import {fetchRecipe } from '../actions';
class SearchBar extends Component {
constructor(props) {
super(props)
this.state = { term: ''};
this.typeRecipe = this.typeRecipe.bind(this)
this.onFormSubmit = this.onFormSubmit.bind(this);
}
onFormSubmit(e) {
e.preventDefault()
this.props.fetchRecipe(this.state.term)
}
typeRecipe(e) {
this.setState({term: e.target.value});
}
render() {
return (
<div className="SearchBar">
<Form onSubmit={this.onFormSubmit}>
<input type='text'
value={this.state.term}
placeholder='ciao'
onChange={this.typeRecipe}
/>
<br/>
<Button id='ciao' className='btn-success'>Submit</Button>
</Form>
</div>
);
}
}
function mapDispatchToProps(dispatch) {
return bindActionCreators({ fetchRecipe }, dispatch);
}
export default connect(null, mapDispatchToProps)(SearchBar);
Action creator
import axios from 'axios';
export const FETCH_RECIPES = 'FETCH_RECIPES';
const API_KEY = 'xxx';//not the real one.
export function fetchRecipe() {
const request = axios.get(`http://food2fork.com/api/search?key=${API_KEY}&q=shredded%20chicken`);
return (dispatch) => {
request.then(({data}) =>{
dispatch({ type: FETCH_RECIPES, payload: data})
})
}
}
reducer
import { FETCH_RECIPES } from '../actions';
export default function (state = {}, action) {
switch(action.type) {
case FETCH_RECIPES:
const newState = action.payload.data;
return newState;
default:
return state
}
}
combineReducer (index)
import recipeReducer from '../reducers/recipes_reducer';
import { combineReducers } from 'redux';
const rootReducer = combineReducers({
recipes: recipeReducer
});
export default rootReducer;

Mistake is in the reducer return statement.
export default function (state = {}, action) {
switch(action.type) {
case FETCH_RECIPES:
const newState = {...state, data : action.payload.data};
return newState;
default:
return state
}
}
Here we are adding data key to the reducer state, to access this you can use do this in you container :
export default connect((state)=>{
var mapStateToProps = {};
if(state.recipes.data) {
mapStateToProps['recipes'] = state.recipes.data
}
return mapStateToProps;
}, mapDispatchToProps)(SearchBar);
and recipes data will be available as this.props.recipes.

Fetched API Data not recognized after handling the promise with a Middleware

I have been building a React-Redux application to display some weather data (openweathermap.org API) if a button gets clicked.
Somehow when the Container is rendered the data are not arriving, even if I managed to handle the promise using Axios.
As you can see in the console.log, the 'tempo' object is empty once it arrives in the container. Then, once the button is clicked, the request correctly arrives on the container and 'tempo' gets the data I want to render.
The problem occurs when I try to access those properties arrived after that the onClick() event was fired. They do not exist yet, so the whole components throw an error.
I think there is some problem with the async await response managed in the Axios request but I cannot find it.
Sorry if the explanation was not properly technical.
I remain at disposal for clarifications.
Action Creator with the API request
import axios from 'axios';
export const GET_CECCIOLA = 'GET_CECCIOLA';
export function submitWeather() {
const url = 'https://api.openweathermap.org/data/2.5/weather?appid=ce6111c5cb481755173214d6bf62f51a&q=Cecciola,it';
const cecciola = axios.get(url);
return {
type: 'GET_CECCIOLA',
payload: cecciola
}
}
Container responsible for the rendering when button is clicked
import React, { Component } from 'react';
import {connect} from 'react-redux';
class CecciolaTime extends Component {
render() {
console.log(this.props.tempo)
return (
<div>
<h2>{this.props.tempo}
</h2>
</div>
);
}
}
function mapStateToProps ({ tempo }) {
return { tempo };
}
export default connect(mapStateToProps)(CecciolaTime);
Container with the onClick() method
import React, {Component} from 'react';
import { connect } from 'react-redux';
import { bindActionCreators } from 'redux';
import {submitWeather } from '../actions/index';
class SearchBar extends Component {
constructor(props) {
super(props)
this.getWeather = this.getWeather.bind(this);
}
getWeather(e) {
e.preventDefault();
this.props.submitWeather(e);
}
render() {
return (
<form>
<button onClick={this.getWeather}>
tempo a Cecciola
</button>
</form>
)
}
}
function mapDispatchToProps(dispatch) {
return bindActionCreators({ submitWeather }, dispatch);
}
export default connect(null, mapDispatchToProps)(SearchBar);
Reducer
import { GET_CECCIOLA } from '../actions/index';
export default function(state = [], action) {
switch (action.type) {
case GET_CECCIOLA:
return [action.payload.data, ...state];
}
return state;
}
Reducer_Index
import { combineReducers } from 'redux';
import CecciolaReducer from './cecciola_reducer';
export default combineReducers({
tempo: CecciolaReducer
})
Store (I am using Redux-Promise as middleware)
import React from 'react';
import './index.css';
import App from './components/App';
import { render } from 'react-dom';
import { Provider } from 'react-redux';
import { createStore, applyMiddleware } from 'redux';
import rootReducer from './reducers'
import ReduxPromise from 'redux-promise';
const storeWithMiddleware = applyMiddleware(ReduxPromise)(createStore);
render(
<Provider store={storeWithMiddleware(rootReducer)}>
<App />
</Provider>,
document.getElementById('root')
)

If you are trying to display non-existing property in tempo object and it fails - the most common way to handle it - just check if this property exists, like that:
import React, { Component } from 'react';
import {connect} from 'react-redux';
class CecciolaTime extends Component {
render() {
const { name } = this.props.tempo
return (
<div>
{/* Check if name exists then display */}
<h2>{name && name}</h2>
</div>
);
}
}
function mapStateToProps ({ tempo }) {
return { tempo };
}
export default connect(mapStateToProps)(CecciolaTime);
NOTE: You're trying to render an object { this.props.tempo } in h2 tag, which can cause another error.
UPDATE (from comments): I've find the issue, it was because you're setting result into array and it's actually keeped in 0 index in array. So you can access to your variables via this.props.tempo[0].name. To avoid this mess just use object instead of array as initial state, it's much easier to handle then.
I've created sandbox for you with working code (click to see).
Hope it will helps.

React Native Redux Reducer not working

I'm attempting to implement redux into a relatively simple app, however my actions don't seem to be triggering the reducers properly. Through console logging the action seems to be firing, but the respective reducer isn't being executed.
App.js:
import {Provider} from 'react-redux';
import configureStore from './src/config/configureStore.js';
const store = configureStore();
export default class App extends React.Component {
render() {
return (
<Provider store = {store}>
<RootStack />
</Provider>
);
}
}
configureStore.js:
import {createStore, applyMiddleware} from 'redux';
import reducers from '../reducers';
import thunk from 'redux-thunk';
export default function configureStore(initialState) {
const store = createStore (
reducers,
applyMiddleware(thunk)
);
return store;
}
actions/index.js:
export const saveRisk = (payload) => {
console.log('saved RISK!');
return (dispatch) => {
dispatch({type: 'risk_chosen',payload: payload});
}
}
reducers/index.js:
import { combineReducers } from 'redux';
import RiskReducer from './RiskReducer';
export default combineReducers({
risk_level: RiskReducer
});
RiskReducer.js
const INITIAL_STATE = {risk_level: false};
export default (risk = INITIAL_STATE, action) => {
if(action.type === 'risk_chosen') {
console.log('RISK REDUCER SUCCESSFUL')
return {
...risk, risk_level: action.payload
};
}
console.log('REDUCER RISK:');
console.log(risk);
return risk;
}
RiskTolerance.js (A child component within RootStack which is using redux):
import { connect } from 'react-redux';
import {saveRisk} from '../../actions'
#connect(state => ({risk_level: state.risk_level.risk_level}, {saveRisk}))
export default class RiskTolerance extends React.Component {
// ...
componentDidMount(){
console.log(this.props.risk_level);
// ^^returns undefined, despite the reducer initializing it to "false"
let riskVal = 'something'
this.props.saveRisk(riskVal)
}
// ...
}
EDIT: I have changed the initial value in the reducer to an appropriate object but my reducer is still not working after the action is called. Any ideas?
Thank you!

There is problem with initial state in your reducer. Make changes as shown below:
INITIAL_STATE = { risk_level: false }

Figured it out, when calling the action I needed to write:
this.props.dispatch(this.props.saveRisk(riskVal))
Thanks for your help everyone!

Redux action not triggering reducers

Problem
I wired up my react application with a Redux store, added an api action to gather data from my backend including middleware redux-promise. Most everything seems to work as I can see my store in the React web editor along with the combine reducer keys. When I have my action called, it works and console logs the completed promise. However, my reducers never run. I thought it was an issue with my dispatch on the main container, but I've tried every way that I can think of at this point - regular dispatch() and bindActionCreators. HELP!
Index.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.js';
import { createStore, applyMiddleware } from 'redux';
import { Provider } from 'react-redux';
import promiseMiddleware from 'redux-promise';
import RootReducer from './reducers';
const createStoreWithMiddleware = applyMiddleware(promiseMiddleware)(createStore)
let store = createStore(RootReducer);
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.getElementById('root'));`
Combine Reducers
import { combineReducers } from 'redux';
import ReducerGetPostings from './reducer_get_postings'
const rootReducer = combineReducers({
postingRecords: ReducerGetPostings
})
export default rootReducer;
Reducer
import { FETCH_POSTINGS } from '../actions/get_postings'
export default function (state = null, action) {
console.log('action received', action)
switch (action.type) {
case FETCH_POSTINGS:
return [ action.payload ]
}
return state;
}
Action API
import axios from 'axios';
import { url } from '../api_route';
export const FETCH_POSTINGS = 'FETCH_POSTINGS'
export function fetchpostings() {
const postingRecords = axios.get(`${url}/api/postings`)
console.log('Postings', postingRecords)
return {
type: FETCH_POSTINGS,
payload: postingRecords
};
}
Container
import { connect } from 'react-redux';
import { bindActionCreators } from 'redux'
import { fetchpostings } from '../../actions/get_postings.js'
class Dashboard extends Component {
//....lots of other functionality already built here.
componentDidMount() {
axios.get(`${url}/api/postings`)
.then(res => res.data)
.then(
(postingRecords) => {
this.setState({
postingData: postingRecords,
postingOptions: postingRecords
});
},
(error) => {
this.setState({
error
})
}
)
// primary purpose is to replace the existing api call above with Redux Store and fetchpostings action creator
fetchpostings()
}
}
function mapDispatchToProps(dispatch) {
// return {actions: bindActionCreators({ fetchpostings }, dispatch)}
return {
fetchpostings: () => dispatch(fetchpostings())
}
}
export default connect(null, mapDispatchToProps)(Dashboard);

You are not dispatching your action, when you call fetchpostings() in componentDidMount you are calling the method imported from actions/get_postings.js, not the method that will dispatch.
Try this.props.fetchpostings() instead.
You also did not bind state to props you need to do that as well.

Redux ReactJS : How Components have access to the store?

for starting, i saw many questions which looks like mine on stackoverflow but i think i miss something, this is why i'm asking this question.
I have a Maincomponent in my app which add datas to my store using the action addDatas.
This part works, i can access to my store in the context and in the children of MainComponent with this.props.
But when i go to OtherComponent (which is a basic component where i just want to show all the datas collected in MainComponent) my store seems to be empty.
Can someone tells me what i'm doing wrong and what OtherComponent should looks like for access the datas i set in the store when i was using MainComponent.
Thanks.
index.js
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './components/App';
import { Provider } from 'react-redux';
import { createStore } from 'redux';
import reducer from './reducers'
const store = createStore(reducer);
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.getElementById('root')
);
reducers.js
import { ADD_DATAS } from '../constants';
const reminder = (action) => {
switch (action.type) {
case ADD_DATAS:
return {
datas: action.datas,
id: action.id
};
default:
return {
text: action.text,
id: action.id
};
}
}
const reminders = (state = [], action) => {
let reminders = null;
switch (action.type) {
case ADD_DATAS:
reminders = [...state, reminder(action)];
return reminders;
default:
return state;
}
}
export default reminders;
Action.js
import {ADD_DATAS} from '../constants';
// ADD_DATAS = 'ADD_DATAS' in constants
export const addDatas = (text, id) => {
const action = {
type: ADD_DATAS,
datas: text,
id: id
}
return action;
}
App.js
import React, { Component } from 'react'
import { BrowserRouter as Router, Switch, Route } from 'react-router-dom'
import RouterComponent from '../Router/RouterComponent';
import OtherComponent from './OtherComponent';
import MainComponent from './MainComponent';
class App extends Component {
render() {
return (
<div className="container-fluid">
<div className="row">
<Sidebar />
<Router>
<RouterComponent>
<Switch>
<Route exact path="/oth" component={OtherComponent}/>
<Route exact path="/main" component={MainComponent}/>
<Route exact path="/" component={MainComponent}/>
</Switch>
</RouterComponent>
</Router>
</div>
</div>
);
}
}
export default App;
MainComponent.js
import React, { Component } from 'react';
import { connect } from 'react-redux'
import { bindActionCreators } from 'redux'
import { addDatas } from '../actions'
class MainComponent extends Component {
addDataStore(text, id){
this.props.addDatas(text, id)
}
render(){
return ( .... )
}
}
function mapDispatchToProps(dispatch){
return bindActionCreators({addDatas}, dispatch);
}
function mapStateToProps(state){
return {
reminders: state
}
}
export default connect(mapStateToProps, mapDispatchToProps)(MainComponent);
OtherComponent.js
import React, { Component } from 'react';
import { connect } from 'react-redux'
class OtherComponent extends Component {
render(){
console.log(this.props.reminders)
}
}
function mapStateToProps(state){
return {
reminders: state
}
}
export default connect(mapStateToProps)(OtherComponent);
Sidebar.js
import React, { Component } from 'react';
import '../css/sidebar.css';
export default class Sidebar extends Component {
render(){
return (
<nav className="col-2 col-md-2 sidebar">
<div className="sidebar-logo">
<a href="/main">
MainComponent
</div>
</a>
</div>
<ul >
<li >
<a href="/main" >
MainComponent
</a>
</li>
<li >
<a href="/oth" >
OtherComponent
</a>
</li>
</ul>
</nav>
)
}
}

To Understand this we first need to understand the below snippet
export default connect(mapStateToProps, mapDispatchToProps)(MainComponent);
we are passing mapStateToProps function to the connect method which we get from react-redux. So let's Understand how connect works and what it actually does
1. It calls your mapStateToProps function and passes the current value of (redux state/ redux store) to the function.
2. Then whatever value is returned by the mapStateToProps function after execution is passed down as props to the mainComponent(in your case).
So Since the child component for the main component is not having connect statement the props are not available to it.
You can make the redux state available as props by two was
1. Passing it down from main component as follows inside mainComponent.js render method we have
import React, { Component } from 'react';
import { connect } from 'react-redux'
import { bindActionCreators } from 'redux'
import { addDatas } from '../actions'
class MainComponent extends Component {
addDataStore(text, id){
this.props.addDatas(text, id)
}
render(){
return (
<Child1 reminders={this.props.reminders}/*can be accessed as this.props.reminders*//>
<Child2 reminders={this.props.reminders}/*can be accessed as this.props.reminders*//>
)
}
}
function mapDispatchToProps(dispatch){
return bindActionCreators({addDatas}, dispatch);
}
function mapStateToProps(state){
return {
reminders: state
}
}
export default connect(mapStateToProps, mapDispatchToProps)(MainComponent);
2.Another way to do this will be using connect Statement inside your child component as well
export default connect(mapStateToProps, mapDispatchToProps)(MainComponent);
class Child1 extends Component{
.....
}
function mapDispatchToProps(dispatch){
return bindActionCreators({addDatas}, dispatch);
}
function mapStateToProps(state){
return {
reminders: state
}
}
export default connect(mapStateToProps, mapDispatchToProps)(Child1);//need to change here must be same as className

You should connect your OtherComponent to redux store as well using connect HoC.

You need to connect other components with mapStateToProps and mapDispatchToProps functions as you do in MainComponents.js
import React, { Component } from 'react';
import { connect } from 'react-redux'
import { bindActionCreators } from 'redux'
import { addDatas } from '../actions'
class OtherComponent extends Component {
addDataStore(text, id) {
this.props.addDatas(text, id)
}
render() {
}
}
function mapDispatchToProps(dispatch) {
return bindActionCreators({ addDatas }, dispatch);
}
function mapStateToProps(state) {
return {
...state
}
}
export default connect(mapStateToProps, mapDispatchToProps)(OtherComponent);

You would connect the otherComponent as well using connect HOC, in order to access the Store. Once you have a component connected the Store in the Hierarchy you can pass the data as props on to its children. However you do need to connect the top level component/s to store
import React, { Component } from 'react';
import { connect } from 'react-redux'
class OtherComponent extends Component {
render(){
console.log(this.props.reminders)
}
}
function mapStateToProps(state){
return {
reminders: state
}
}
export default connect(mapStateToProps)(OtherComponent);

Well,
my problem wasn't on my implementation of Redux but on the fact that i used href for navigate between my components.
The problem was that my Sidebar component wasn't in the Router component, then i had to save the history in the redux store and call history.push in my sidebar component with the history i saved before.
In all my components inside the router i added in the constructor:
constructor(props){
super(props);
...
this.props.addHistory(props.history);
}
addHistory add history if it doesn't already exist.
Then in my sidebar, i use the history in the store for use the push function:
for (var e in this.props.reminders){
if(this.props.reminders[e].history !== undefined ){
this.props.reminders[e].history.push('/oth');
}
}
I don't know if it's the cleanest way to do this, but it works.