How to call mapStateToProps in react component to get Redux stores - javascript

I am trying to get the Redux state that is stored to be set to a component's props. My components implementation is below
import React, { Component } from 'react';
import {connect} from 'react-redux';
class Characters extends Component {
render() {
console.log('props', this.props);
return(
<div>
<h4>Characters</h4>
</div>
)
}
}
const mapStateToProps = state => {
return {
characters: state.characters
}
}
export default connect()(Characters);
I have my reducers set up like following. Now my console.log() is printing out a dispatch object not the props. I am not sure what else I need to do to set the component's props. I have tested my reducers and they seem to work fine. I am having trouble setting the component's props to the redux store. Below is my main reducer.
import { combineReducers } from 'redux';
import characters from './characters_reducer';
import heroes from './heroes_reducer';
const rootReducers = combineReducers({
characters,
heroes
});
export default rootReducers;
Not sure what am I doing wrong here. A little help and a hinge to the right direction would help a lot. Thanks :)

You forgot to pass mapStateToProps to connect:
export default connect(mapStateToProps)(Characters);

You need to pass in your actionCreators and your mapStateToProps function to the connect function in order to be able to access the store from the component:
export default connect(mapStateToProps)(Characters);

Related

Not getting props from child component in Redux

I want to get props from Redux in the child component. But {this.props} is empty object. I am using react-redux connect to get the props. It is working in parent component and we can pass to child component to get the props but I need to get from child component
Login
```import React, { Component } from 'react'
import { Test } from './Test'
export default class Login extends Component {
render() {
return (
<div>
<Test hi=""/>
</div>
)
}
}```
Test
import React, { Component } from 'react'
import { connect } from 'react-redux'
export class Test extends Component {
render() {
console.log(this.props)
return (
<div>
vddfff
</div>
)
}
}
const mapStateToProps = (state) => ({
})
const mapDispatchToProps = (dispatch) => {
return {
selectedData: (val) => {
console.log("object")
}
}
}
export default connect(mapStateToProps, mapDispatchToProps)(Test)
The problem here is that you are trying to use the Test component you wrote instead of the Higher order component which is being returned by the connect() from react-redux
You don't need to export the Test class.
In login.js file, use
import Test from './Test'
instead of
import {Test} from './Test'
See it in action here.
https://codesandbox.io/s/sample-test-app-q5srf
You used the wrong component. In login you need to import:
import Test from './Test'
You imported Test wich is not connected to redux (that pushes the redux props).

Store subscribe not working in external component

So technically I have 2 components, I dispatch event from 1st, I want detect this change in 2nd.
I did everything as in Redux docs about Store subscribing : https://redux.js.org/api/store#subscribe. Unfortunatelly, it's not working for me.
This is my 1st react project.
(vue/x is better :] )
import React, {Component} from 'react';
import reducers from '../../reducers'
import { Dropdown } from 'semantic-ui-react'
import {translate} from "../../actions";
import createStore from "../../createStore";
const store = createStore(reducers)
class Component1 extends Component {
componentDidMount() {
store.subscribe(() => console.log(1));
}
updateTexts(lang) {
store.dispatch(translate(lang));
}
render() {
this.dropdown = <Dropdown
onChange={this.updateTexts}
/>
return (
<div className={"lang-switcher"}>
<div className={"select-lang"}>
{this.dropdown}
</div>
</div>
);
}
}
export default Component1
import React, {Component} from 'react';
import axios from 'axios';
import {Animate} from 'react-animate-mount';
import createStore from "../../createStore";
import reducers from "../../reducers";
const store = createStore(reducers);
export default class Component2 extends Component {
componentDidMount() {
store.subscribe(console.log(2));
}
render() {
return (
<div className="box">
{Something}
</div>
);
}
}
I want that Component2 will detect state change done by Component1.
Reducer is working correctly, updates state after dispatching.
If you're using React, you should be using the React-Redux library to handle interacting with the store.
That said, it also looks like you're creating two different store instances, one in each component file. So, Component 2 doesn't know about the store instance in Component 1's file.
Please create a script Store.js, and import for each component.
When you use export, that will create a singleton from your export const:
Store.js
import reducers from '../../reducers'
import createStore from "../../createStore"
export default createStore(reducers)
and use as:
import store from "./Store";
/* REMOVE const store = createStore(reducers); */

React Redux Mapping state to props not working

So I'm trying to learn React with Redux and so far I think I've been able to work out most of the code needed to make it work but I'm having an issue with getting my state passed down to my component. I am using Visual Studio 2017's ASP.NET Core project template that has react and redux boilerplate codes and they used this:
export default connect(
state => state.weatherForecasts,
dispatch => bindActionCreators(actionCreators, dispatch)
)(FetchData);
I tried doing the same thing with my own component like so:
export default connect(
state => state.lecture,
dispatch => bindActionCreators(actionCreators, dispatch)
)(LectureTable);
but when trying to access the contents of my props, the properties I want to get are tagged as undefined. I checked through Redux devtools that my initial state exists but my component is unable to see the props I'm trying to pass to it. The weird thing is I just imitated the boilerplate code but it isn't working yet the boilerplate code works just fine (ie I can go to the component and log out its initial state).
Since I'm following the format used by Visual Studio,my actioncreators, reducers, and constants are in one file shown below:
const GET_LECTURES = "GET_LECTURES";
const initialState = {
lectures: [],
selectedLecture: {},
isLoading: false,
test: 0
};
export const actionCreators = {
requestLectures: isLoading => async (dispatch) =>
{
if (!isLoading) {
// Don't issue a duplicate request (we already have or are loading the requested data)
return;
}
dispatch({ type: GET_LECTURES });
const url = `api/lecture/`;
const response = await fetch(url);
const lectures = await response.json();
dispatch({ type: RECEIVE_LECTURES, payload: lectures });
}
};
export const reducer = (state = initialState, action) => {
switch (action.type) {
case GET_LECTURES:
return { ...state, isLoading: true };
default:
return state;
}
};
I'm sorry if its all messy. I'm really just starting to begin to understand redux..
Edit
My component code:
import React, { Component } from 'react';
import {Button, Table, Label, Menu, Icon} from 'semantic-ui-react';
import { bindActionCreators } from 'redux';
import { connect } from 'react-redux';
import {actionCreators} from './../../store/Lecture';
export class LectureTable extends Component {
componentWillMount(){
// this.props.requestLectures(this.props.isLoading);
console.log(this.props.test);
}
render() {
return (
<Table size='large'>
{/*removed to make it cleaner..currently only has static data too lol*/}
</Table>
)
}
}
export default connect(
state => state.lecture,
dispatch => bindActionCreators(actionCreators, dispatch)
)(LectureTable);
where my store is configured:
import { applyMiddleware, combineReducers, compose, createStore } from 'redux';
import thunk from 'redux-thunk';
import { routerReducer, routerMiddleware } from 'react-router-redux';
import * as Lecture from './Lecture';
import * as Counter from './Counter';
import * as WeatherForecasts from './WeatherForecasts';
export default function configureStore(history, initialState) {
const reducers = {
lecture: Lecture.reducer,
counter: Counter.reducer,
weatherForecasts: WeatherForecasts.reducer
};
const middleware = [
thunk,
routerMiddleware(history)
];
// In development, use the browser's Redux dev tools extension if installed
const enhancers = [];
const isDevelopment = process.env.NODE_ENV === 'development';
if (isDevelopment && typeof window !== 'undefined' && window.devToolsExtension) {
enhancers.push(window.devToolsExtension());
}
const rootReducer = combineReducers({
...reducers,
routing: routerReducer
});
return createStore(
rootReducer,
initialState,
compose(applyMiddleware(...middleware), ...enhancers)
);
}
my index.js
import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import { ConnectedRouter } from 'react-router-redux';
import { createBrowserHistory } from 'history';
import configureStore from './store/configureStore';
import App from './pages/App';
import registerServiceWorker from './registerServiceWorker';
// Create browser history to use in the Redux store
const baseUrl = document.getElementsByTagName('base')[0].getAttribute('href');
const history = createBrowserHistory({ basename: baseUrl });
// Get the application-wide store instance, prepopulating with state from the server where available.
const initialState = window.initialReduxState;
const store = configureStore(history, initialState);
const rootElement = document.getElementById('root');
ReactDOM.render(
<Provider store={store}>
<ConnectedRouter history={history}>
<App />
</ConnectedRouter>
</Provider>,
rootElement);
registerServiceWorker();
The first argument to connect() should be a function that returns an object - with the props you want added as keys, and their value being the value from state. e.g.
state => ({ lecture: state.lecture })
I found the solution. First of all I'm a noob both to stackoverflow and to react so I apoligize for all my inconsistencies (if thats the right term?).
What I found out:
I am using react router
I was doing the connect method to a subcomponent of the component being rendered by the router
I placed the connect method to the parent component and it worked
Some notes:
state => state.lecture still works
I will take all of your advices to heart and change my code accordingly
The only reason I was adamant with solving the problem using the code I had was because I couldn't accept the fact that boilerplate code wouldn't work unless I had done something specifically different from what the boilerplate did. I just didn't take into account that the router played a huge role with it.
I repeat...I'm a react noob so I'm sorry for wasting your time T_T
Edit again:
I was able to connect a different child component with the Redux store. I'm trying to look at why I still can't do it for that specific component that caused me to ask this question. I'll update my answer once I find the reason.
I think in their example weatherForecasts is an object. In your example lectures seems to be an array so I suggest to rewrite your mapStateToProps function like this if you only need to get the lectures prop
state => ({ lectures: state.lectures})
if you need the whole state you can have state => state so you can access the props this.props.test and this.props.lectures
Keep in mind that mapStateToProps should return an object, not an array. By the way, in your reducer the field name is lectures (plural) not lecture so state => state.lecture will be undefined
Rick, your connect argument should be something like:
export default connect( state => {
return {
test: state.lecture // Or any value
}
})(LectureTable);
You're trying to console log the test prop, so you should include it in your connect call.
I think by doing the following steps, you can solve the issue:
First you need to call two functions when you want to connect your component to application state, one is mapDispatchToProps and another one is mapStateToProps, for your code to be clean, its better to define these functions separately and then pass them by name to connect, but if you want to use your own way you should do these changes: (assuming your reducer name is lecture from your combineReducers, and assuming you are calling requestLectures with this syntax: this.props.lectureActions.requestLectures() and importing lectureActions from the file you have written lecture related actions) :
export default connect(
state => state.lecture.lectures,
dispatch => {lectureActions: bindActionCreators(lectureActions, dispatch)}
)(LectureTable);
from above code, you do not need to export an object that contains the actions like actionCreators, you should export the requestLectures function out of it independently
add below case to your reducer so that when getting the lectures succeeds the state of the application gets updated with the lectures:
case RECEIVE_LECTURES:
return { ...state, isLoading: false, lectures: payload.lectures };
default:
return state;
}
You have two problems here.
You are defining mapStateToProps function as the first argument to connect wrong. As many of answers explain this now you should use it like, this:
export default connect(
state => ( { lecture: state.lecture } ),
dispatch => bindActionCreators(actionCreators, dispatch)
)(LectureTable);
Now, you have a lecture prop as your state. You can reach it with this.props.lecture. But in your componentWillMount method, you are trying to log it like this.props.test. It should be this.props.lecture.test.
By the way, try to use componentDidMount instead of componentWillMount since it will be deprecated in the future releases.

How to dispatch an action to change the inner state in a react component

Can I dispatch an action in the redux to change the inner state of a react component?
I have a state managed by the react state and I want to do some async stuff in the middleware of redux so that I can manage all the side effect in only one place. However, I want to change the inner state of react after I finished my async call and I don't want to manage this state by redux(You will need to pass too many things into the actions). Is there a way to fire up an action to change the react state by redux? Thanks.
You can do it using componentWillReceiveProps lifecycle hook.
So, you should connect to the updates using connect from react-redux and then update your local state.
For example:
SomeContainer.jsx
import React from 'react';
import { connect } from 'react-redux';
import { yourCustomAsyncAction } from '../actions';
import SomeComponent from './components';
const mapStateToProps = state => {
return {
someValue: state.someState.someValue
};
};
export default connect(mapStateToProps, { yourCustomAsyncAction })(SomeComponent));
SomeComponent.jsx
import React, { Component } from 'react';
class SomeComponent extends Component {
constructor(props) {
super(props);
this.state = {
someLocalValue: '',
}
}
componentWillReceiveProps(nextProps) {
// someValue - value which we passed from redux in container
const { someValue } = nextProps;
if (someValue !== this.state.someLocalValue) {
this.setState({ someLocalValue: someValue });
}
}
render() {
return <div> Here will be updated value via Redux: {this.state.someLocalValue} </div>
}
}
export default SomeComponent;
NOTE: componentWillReceiveProps is going to be deprecated starting with React version 16.3 (which should be released soon) and will be removed with 17 version. The new static method is introduced named getDerivedStateFromProps. See more here.
Hope it will helps.

How to get dispatch redux

I'm learning redux and react. I am following some tutorials, in order to make a app.
I have this action:
export function getDueDates(){
return {
type: 'getDueDate',
todo
}
}
this is the store:
import { createStore } from 'redux';
import duedates from './reducers/duedates'
export default createStore(duedates)
This is the reducer:
import Immutable from 'immutable'
export default (state = Immutable.List(['Code More!']), action) => {
switch(action.type) {
case 'getDueDate':
return state.unshift(action.todo)
default:
return state
}
}
and in the entry point js I have this:
import React from 'react';
import ReactDOM from 'react-dom';
import store from './app/store'
import { Provider } from 'react-redux'
import App from './app/Components/AppComponent';
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.getElementById('app')
);
Now, (according to some examples), I should call getDueDate from the dispatch but I dont get how to get the dispatch on the component, to trigger the action
Use connect from react-redux package. It has two functions as params, mapStateToProps and mapDispatchToProps, which you are interested in now. As per answer from Nick Ball, which is partially right, you will be exporting like this:
export default connect(mapStateToProps, mapDispatchToProps)(App)
and your mapDispatchToProps will look something like this:
function mapDispatchToProps (dispatch, ownProps) {
return {
getDueDate: dispatch(getDueDate(ownProps.id))
}
}
as long as your component connected to the store has property id passed from above, you'll be able to call this.props.getDueDate() from inside of it.
EDIT: There is probably no need of using an id in this case, however my point was to point out that props go as second parameter :)
The missing piece here is the connect function from react-redux. This function will "connect" your component to the store, giving it the dispatch method. There are variations on how exactly to do this, so I suggest reading the documentation, but a simple way would be something like this:
// app/Components/AppComponent.js
import { connect } from 'react-redux';
export class App extends React.Component {
/* ...you regular class stuff */
render() {
// todos are available as props here from the `mapStateToProps`
const { todos, dispatch } = this.props;
return <div> /* ... */ </div>;
}
}
function mapStateToProps(state) {
return {
todos: state.todos
};
}
// The default export is now the "connected" component
// You'll be provided the dispatch method as a prop
export default connect(mapStateToProps)(App);

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