Mobx react never update - javascript

I'm trying to understand mobx implementation in React. I used create react app and update default configuration to use decorators. Then I created a simple store like this :
EDIT : after Ben Hare (thanks to him !) reply I updated my code like this :
index.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import MessageStore from "./store/messages";
ReactDOM.render(<App store={new MessageStore()} />,
document.getElementById('root'));
** App.js **
import React from "react";
import { observer } from "mobx-react";
#observer
export default class App extends React.Component {
constructor(props) {
super(props);
this.store = props.store;
}
render() {
return <ul>
{ this.store.allMessages.map((msg) => {
return <li key={msg}>{msg}</li>
})}
</ul>
}
}
messages.js
import {action, observable, computed} from "../../node_modules/mobx/lib/mobx";
export default class MessageStore {
#observable messages = ["My first message"];
constructor() {
setInterval(() => {
// Add some random messages every second
this.addMessage(Math.random());
}, 1000);
}
#action addMessage(msg) {
this.messages.push(msg);
}
#computed get allMessages() {
return this.messages;
}
}
The first message is displayed, but component never update when setInterval add message into the store. Can you help me ?

Works for me:
https://codesandbox.io/s/LgQXNBnNW
Did you see any errors in the browser log or terminal?

Check my approach please. Maybe it will help:
MobX store:
import { action, observable, runInAction } from 'mobx'
class DataStore {
#observable data = null
#observable error = false
#observable fetchInterval = null
#observable loading = false
//*Make request to API
#action.bound
fetchInitData() {
const response = fetch('https://poloniex.com/public?command=returnTicker')
return response
}
//*Parse data from API
#action.bound
jsonData(data) {
const res = data.json()
return res
}
//*Get objects key and push it to every object
#action.bound
mapObjects(obj) {
const res = Object.keys(obj).map(key => {
let newData = obj[key]
newData.key = key
return newData
})
return res
}
//*Main bound function that wrap all fetch flow function
#action.bound
async fetchData() {
try {
runInAction(() => {
this.error = false
this.loading = true
})
const response = await this.fetchInitData()
const json = await this.jsonData(response)
const map = await this.mapObjects(json)
const run = await runInAction(() => {
this.loading = false
this.data = map
})
} catch (err) {
console.log(err)
runInAction(() => {
this.loading = false
this.error = err
})
}
}
//*Call reset of MobX state
#action.bound
resetState() {
runInAction(() => {
this.data = null
this.fetchInterval = null
this.error = false
this.loading = true
})
}
//*Call main fetch function with repeat every 5 seconds
//*when the component is mounting
#action.bound
initInterval() {
if (!this.fetchInterval) {
this.fetchData()
this.fetchInterval = setInterval(() => this.fetchData(), 5000)
}
}
//*Call reset time interval & state
//*when the component is unmounting
#action.bound
resetInterval() {
if (this.fetchInterval) {
clearTimeout(this.fetchInterval)
this.resetState()
}
}
}
const store = new DataStore()
export default store

Related

TypeError: Cannot read property 'products' of undefined Mobx React Native

Mobx giving me this error, and I don't know what is going on, there is no error in my code, what I make wrong? I tried so much fix this problem, hours and hours, someone knows what wrong I do??
stores/index.ts
import ProductStore from './product.store';
class RootStore {
products: ProductStore;
constructor() {
this.products = new ProductStore();
}
}
const store = new RootStore();
export {RootStore, ProductStore};
export default store;
stores/product.store.ts
import {WalmartApi} from '../api';
import {action, makeAutoObservable, runInAction} from 'mobx';
export default class ProductStore {
products = [];
constructor() {
makeAutoObservable(this);
}
#action
getProducts = async (searchQuery: string): Promise<void> => {
const snapshot = await WalmartApi.getProductsBySegment(searchQuery);
console.log({snapshot});
runInAction(() => {
this.products = snapshot;
});
};
}
hooks/userStores.tsx
import React from 'react';
import {MobXProviderContext} from 'mobx-react';
import store from '#stores';
export const useStores = (): typeof store => {
return React.useContext(MobXProviderContext).rootStore;
};
screens/Home.tsx
const {products} = useStores();
const onInit = () => {
products.getProducts('Playstation5');
};
useEffect(() => {
onInit();
});

React Mobx can't display observable contents, very simple app

Very simple app, I'm trying to display content from my API using Mobx and Axios, here's my Axios agent.ts:
import { ITutorialUnit } from './../model/unit';
import axios, { AxiosResponse } from "axios";
//set the base URL
axios.defaults.baseURL = "http://localhost:5000/api";
//store our request in a const
const responseBody = (response: AxiosResponse) => response.data;
const requests = {
get: (url: string) => axios.get(url).then(responseBody),
};
//create a const for our activty's feature,all our activities' request are go inside our Activities object
const TutorialUnits = {
list: ():Promise<ITutorialUnit[]> => requests.get("/tutorialunits"),
};
export default{
TutorialUnits
}
then I call this agent.s in a store:
import { ITutorialUnit } from "./../model/unit";
import { action, observable } from "mobx";
import { createContext } from "react";
import agent from "../api/agent";
class UnitStore {
#observable units: ITutorialUnit[] = [];
//observable for loading indicator
#observable loadingInitial = false;
#action loadUnits = async () => {
//start the loading indicator
this.loadingInitial = true;
try {
//we use await to block anything block anything below list() method
const units = await agent.TutorialUnits.list();
units.forEach((unit) => {
this.units.push(unit);
// console.log(units);
});
this.loadingInitial = false;
} catch (error) {
console.log(error);
this.loadingInitial = false;
}
};
}
export default createContext(new UnitStore());
then I call this in my App component:
import React, { Fragment, useContext, useEffect } from "react";
import { Container } from "semantic-ui-react";
import "semantic-ui-css/semantic.min.css";
import NavBar from "../../features/nav/NavBar";
import { ActivityDashboard } from "../../features/Units/dashboard/tutorialUnitDashboard";
import UnitStore from "../stores/unitStore";
import { observer } from "mobx-react-lite";
import { LoadingComponent } from "./LoadingComponent";
const App = () => {
const unitStore = useContext(UnitStore);
useEffect(() => {
unitStore.loadUnits();
//need to specify the dependencies in dependenciy array below
}, [unitStore]);
//we are also observing loading initial below
if (unitStore.loadingInitial) {
return <LoadingComponent content="Loading contents..." />;
}
return (
<Fragment>
<NavBar />
<Container style={{ marginTop: "7em" }}>
<ActivityDashboard />
</Container>
</Fragment>
);
};
export default observer(App);
Finally, I want to use this component to display my content:
import { observer } from "mobx-react-lite";
import React, { Fragment, useContext } from "react";
import { Button, Item, Label, Segment } from "semantic-ui-react";
import UnitStore from "../../../app/stores/unitStore";
const UnitList: React.FC = () => {
const unitStore = useContext(UnitStore);
const { units } = unitStore;
console.log(units)
return (
<Fragment>
{units.map((unit) => (
<h2>{unit.content}</h2>
))}
</Fragment>
);
};
export default observer(UnitList);
I can't see the units..
Where's the problem? My API is working, I tested with Postman.
Thanks!!
If you were using MobX 6 then you now need to use makeObservable method inside constructor to achieve same functionality with decorators as before:
class UnitStore {
#observable units: ITutorialUnit[] = [];
#observable loadingInitial = false;
constructor() {
// Just call it here
makeObservable(this);
}
// other code
}
Although there is new thing that will probably allow you to drop decorators altogether, makeAutoObservable:
class UnitStore {
// Don't need decorators now anywhere
units: ITutorialUnit[] = [];
loadingInitial = false;
constructor() {
// Just call it here
makeAutoObservable(this);
}
// other code
}
More info here: https://mobx.js.org/react-integration.html
the problem seems to be the version, I downgraded my Mobx to 5.10.1 and my mobx-react-lite to 1.4.1 then Boom everything's fine now.

Redux - How to get data from store and post it

Newbie to Redux here, I have tried to follow a couple tutorials and I am not clear of how Redux actually works. It was mentioned that the store of Redux is to store the state of the whole tree. I have created and used actions, reducers, and store for my program and it works.
The question is, how do I retrieve what is in the store? Lets say after updating my component, how can I retrieve the value inside the component and to post it?
How can I know what changed in my dropdown list and to retrieve it?
Full code in Sandbox here https://codesandbox.io/s/elated-goldberg-1pogb
store.js
import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import rootReducer from './RootReducer';
export default function configureStore() {
return createStore(
rootReducer,
applyMiddleware(thunk)
);
}
ProductsList.js
import React from "react";
import { connect } from "react-redux";
import { fetchProducts } from "./SimpleActions";
class ProductList extends React.Component {
constructor(props)
{
super(props);
this.state = {
selecteditems: '',
unitPrice: 0
}
}
componentDidMount() {
this.props.dispatch(fetchProducts());
}
componentDidUpdate(prevProps, prevState) {
if(prevState.selecteditems !== this.state.selecteditems)
{
this.setState((state, props) => ({
unitPrice: ((state.selecteditems * 1).toFixed(2))
}));
}
}
render() {
const { error, loading, products } = this.props;
if (error) {
return <div>Error! {error.message}</div>;
}
if (loading) {
return <div>Loading...</div>;
}
return (
<div>
<select
name="sel"
className="sel"
value={this.state.selecteditems}
onChange={(e) =>
this.setState({selecteditems: e.target.value})}
>
{products.map(item =>
<option key={item.productID} value={item.unitPrice}>
{item.itemName}
</option>
)}
</select>
<p>Unit Price: RM {this.state.unitPrice} </p>
</div>
);
}
}
const mapStateToProps = state => {
const products = state.productsReducer.items;
const loading = state.productsReducer.loading;
const error = state.productsReducer.error;
return {
products,
loading,
error,
}
};
export default connect(mapStateToProps)(ProductList);
SimpleAction.js
export function fetchProducts() {
return dispatch => {
dispatch(fetchProductsBegin());
return fetch('http://localhost:55959/api/products')
.then(handleErrors)
.then(res => res.json())
.then(results => {
dispatch(fetchProductsSuccess(results));
return results;
})
.catch(error => dispatch(fetchProductsFailure(error)));
};
}
function handleErrors(response) {
if(!response.ok) {
throw Error (response.statusText);
}
return response;
}
export const FETCHPRODUCTS_BEGIN = 'FETCHPRODUCTS_BEGIN';
export const FETCHPRODUCTS_SUCCESS = 'FETCHPRODUCTS_SUCCESS';
export const FETCHPRODUCTS_FAILURE = 'FETCHPRODCUTS_FAILURE';
export const fetchProductsBegin = () => ({
type: FETCHPRODUCTS_BEGIN
});
export const fetchProductsSuccess = products => ({
type: FETCHPRODUCTS_SUCCESS,
payload: {products}
});
export const fetchProductsFailure = error => ({
type: FETCHPRODUCTS_FAILURE,
payload: {error}
});
Thanks in advance!
You will need to pass your action handlers to connect function
connect(mapStateToProps,{actions})(ProductList).
how do I retrieve what is in the store? Lets say after updating my component, how can I retrieve the value inside the component and to post it?
if you want to see how is store change, you can add redux-logger to middleware to see that. when store change, it's likely a props change, you can handle this in function componentDidUpdate.
How can I know what changed in my dropdown list and to retrieve it?
values in dropdown is controlled by "const products = state.productsReducer.items;", productsReducer is controlled by actions you passed in dispatch like this: "this.props.dispatch(fetchProducts());".
I think you should add redux-logger to know more how to redux work, it show on console step by step. It will help you learn faster than you think :D
to retrieve it you forgot the selecteditems
const mapStateToProps = state => {
const products = state.productsReducer.items;
const loading = state.productsReducer.loading;
const error = state.productsReducer.error;
const selecteditems = state.prodcuts.selecteditems;
return {
products,
loading,
error,
selecteditems
};
};
To change it you should connect another function like
const mapDispatchToProps = dispatch => {
return {
onChangeDropdownSelection: (selected)=> dispatch(actions.setSelectedDropdown(selected))
}
}

Not able to return data from getInitialProps() of lower order page component

I have a lower order page component that needs to fetch data in the getInitialProps(). It successfully fetches the data, but it does return as prop in the component.
Below is the code I'm working on
import React, { Component } from 'react';
import DefaultPage from '../hocs/DefaultPage';
import PageLayout from '../components/PageLayout';
import { getJwtFromLocalCookie, getJwtFromServerCookie } from '../utils/auth';
import { getUser } from '../services/users';
class Profile extends Component {
static async getInitialProps(ctx) {
let user;
const jwt = process.browser ? getJwtFromLocalCookie() : getJwtFromServerCookie(ctx.req);
try {
const {data} = await getUser(ctx.query.id, jwt);
user = data;
}
catch (err) {
if(err.code === 404)
ctx.res.statusCode = 404;
}
console.log(user);
return { user };
}
constructor(props) {
super(props);
this.state = { user: null };
}
render() {
console.log(this.props);
return (
<PageLayout
active=""
loggedUser={this.props.loggedUser}
>
</PageLayout>
);
}
}
export default DefaultPage(Profile);
The console.log() in the getInitialProps() does display the correct data, but the console.log() in render() doesn't have the user prop.
Ok, I found the solution, turns out in the getInitialProps() of the higher order component the getInitialProps() of the lower order component was returning a promise and needed to be handled
So, below is the before code of my hoc getInitialProps
static getInitialProps (ctx) {
const loggedUser = process.browser ? getUserFromLocalCookie() : getUserFromServerCookie(ctx.req)
const pageProps = Page.getInitialProps && Page.getInitialProps(ctx);
return {
...pageProps,
loggedUser,
currentUrl: ctx.pathname,
isAuthenticated: !!loggedUser
}
}
And the following is corrected code
static async getInitialProps (ctx) {
const loggedUser = process.browser ? getUserFromLocalCookie() : getUserFromServerCookie(ctx.req)
const pageProps = await (Page.getInitialProps && Page.getInitialProps(ctx));
return {
...pageProps,
loggedUser,
currentUrl: ctx.pathname,
isAuthenticated: !!loggedUser
}
}

Cannot access data request Axios, React-Redux

I am trying to make an API request using Axios in React-Redux environment. On the console everything seems to be fine, however if I try to access any of the data I either get undefined or empty array.
This is my component:
import React, { Component } from 'react';
import { connect } from 'react-redux';
import { discoverMovie } from '../actions'
//Home component
class Home extends Component {
//make request before the render method is invoked
componentWillMount(){
this.props.discoverMovie();
}
//render
render() {
console.log('movie res ',this.props.movies.movies.res);
console.log('movie ',this.props.movies);
return (
<div>
Home
movie
</div>
)
}
};
const mapStateToProps = (state) => {
return{
movies : state.movies
}
}
export default connect(mapStateToProps, { discoverMovie })(Home);
This is my action
import { DISCOVER_MOVIE } from '../constants';
import axios from 'axios';
//fetch movie
const fetchMovie = () => {
const url = 'https://api.themoviedb.org/3/discover/movie?year=2018&primary_release_year=2018&page=1&include_video=false&include_adult=false&sort_by=vote_average.desc&language=en-US&api_key=72049b7019c79f226fad8eec6e1ee889';
let result = {
res : [],
status : ''
};
//make a get request to get the movies
axios.get(url).
then((res) => {
result.res = res.data.results;
result.status = res.status;
return result;
});
//return the result after the request
return result;
}
//main action
const discoverMovie = () =>{
const result = fetchMovie();
//return the action
return {
type : DISCOVER_MOVIE,
payload : result
}
}
export default discoverMovie;
This is the reducer
import { DISCOVER_MOVIE } from '../constants';
//initial state
const initialState = {
movies : {},
query : '',
};
//export module
export default (state = initialState, actions) =>{
switch(actions.type){
case DISCOVER_MOVIE :
return {
...state,
movies : actions.payload
};
default :
return state;
}
}
this is the log that I get from the console
as you can see if I log the entire object I see all data, however if go deep and try to access the result I either get an undefined or an empty array and using redux-dev-tools I noticed that the state does not contain any value.
I read on internet including this portal similar issue but could not find any solution for my issue.
Solution
From official docs:
You may use a dedicated status field in your actions
Basically you need to dispatch action for each state to make an async action to work properly.
const searchQuery = () => {
return dispatch => {
dispatch({
type : 'START',
})
//make a get request to get the movies
axios.get(url)
.then((res) => {
dispatch({type : 'PASS', payload : res.data});
})
.catch((err) => {
dispatch({type : 'FAILED', payload : res.error});
});
}
With redux-thunk it's pretty simple to set up. You just have to make some changes to your store. Out the box, I'm pretty sure redux isn't the most friendly with async and that's why thunk is there.
import { ..., applyMiddleware } from "redux";
import thunk from "redux-thunk";
...
const store = createStore(reducer, applyMiddleware(thunk));
...
Then in your action you'll need to return dispatch which will handle your logic for your axios call.
const fetchMovie = () => {
return dispatch => {
const url = //Your url string here;
axios.get(url).then(res => {
dispatch(discoverMovie(res.data.results, res.status);
}).catch(err => {
//handle error if you want
});
};
};
export const discoverMovie = (results, status) => {
return {
type: DISCOVER_MOVIE,
payload: results,
status: status
};
};
Your reducer looks fine, though with the way my code is typed you'll have status separately. You can combine them into it's own object before returning in discoverMovie, if you need status with the results.
This is my first answer on stack so let me know if I can clarify anything better!

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