Reading about redux-toolkit and thinking that it's a great tool. But how to deal if you have to migrate from a redux switch multi-cases written code? Is there way not to duplicate action methods that are described with cases as logical OR?
const someReducer = (state = {result:1, error: null, text: ""}, action) => {
switch(action.type){
case 'ADD':
case 'SUM':
case 'TOTAL':
return {
...state,
result: state.result + action.payload,
error: null
};
case 'DIVIDE':
return {
...state,
error: true,
text: "some error"
};
case 'MULTIPLY':
return {
...state,
result: state.result*ation.payload,
error: null
};
default:
return state
}
};
So after migrating to RTK it will looks not so handy with duplicating same code:
const someReducer = createSlice({
name: 'someReducer',
initialState: {result:1, error: null, text: ""},
reducers: {
add: (state, { payload }) => { result.state += payload, result.error=null }
total: (state, { payload }) => { result.state += payload, result.error=null }
sum: (state, { payload }) => { result.state += payload, result.error=null }
divide: (state, { payload }) => { result.error=null, result.tex t= "some error" }
multiply: (state, { payload }) => { result.state= result.state * payload, result.error=null }
}});
I am using React with Redux. The Redux devtool console shows that data exists in the state (redux devtools console), but the webpage displays an error saying that the object is undefined (error).
This is my code for my screen:
import React, { useEffect } from "react";
import { useSelector, useDispatch } from "react-redux";
import { listProductDetails } from "../redux/actions/productActions";
const ProductScreen = ({ match }) => {
const dispatch = useDispatch();
const productDetails = useSelector((state) => state.productDetails);
const { loading, error, product } = productDetails;
useEffect(() => {
dispatch(listProductDetails(match.params.id));
}, [dispatch, match]);
return <div>{product.name}</div>;
};
export default ProductScreen;
This is the code for my redux reducer:
import {
PRODUCT_DETAILS_FAIL,
PRODUCT_DETAILS_REQUEST,
PRODUCT_DETAILS_SUCCESS,
} from "../constants";
export const productDetailsReducer = (state = { product: {} }, action) => {
switch (action.type) {
case PRODUCT_DETAILS_REQUEST:
return { loading: true };
case PRODUCT_DETAILS_SUCCESS:
return { loading: false, product: action.payload };
case PRODUCT_DETAILS_FAIL:
return { loading: false, error: action.payload };
default:
return state;
}
};
This is the code for my action:
import axios from "axios";
import {
PRODUCT_DETAILS_FAIL,
PRODUCT_DETAILS_REQUEST,
PRODUCT_DETAILS_SUCCESS,
} from "../constants";
export const listProductDetails = (id) => async (dispatch) => {
try {
dispatch({
type: PRODUCT_DETAILS_REQUEST,
});
const { data } = await axios.get(`/api/products/${id}`);
dispatch({
type: PRODUCT_DETAILS_SUCCESS,
payload: data,
});
} catch (error) {
dispatch({
type: PRODUCT_DETAILS_FAIL,
payload:
error.response && error.response.data.message
? error.response.data.message
: error.message,
});
}
};
I really cannot find the issue here, any help would be greatly appreciated!
I think the problem is when you dispatch PRODUCT_DETAILS_REQUEST action, reducer will override the state value with { loading: true }, and so product will be undefined instead of empty object {}.
So you should return merged object with the previous state in the reducer. e.g. return { ...state, loading: true };
Hope it could help you.
export const productDetailsReducer = (state = { product: {} }, action) => {
switch (action.type) {
case PRODUCT_DETAILS_REQUEST:
return { ...state, loading: true };
case PRODUCT_DETAILS_SUCCESS:
return { ...state, loading: false, product: action.payload };
case PRODUCT_DETAILS_FAIL:
return { ...state, loading: false, error: action.payload };
default:
return state;
}
};
I need to call checkConnection before any other action so I thought of using axios interceptors:
axios.interceptors.request.use(
async config => {
await store.dispatch(checkConnection())
const { requestTime, hash } = intro(store.getState())
return {
...config,
headers: {
'Request-Time': requestTime,
'Api-Hash-Key': hash
}
}
}
)
intro is a reselect selector used to do some 'heavy' computing on serverTime (serverTime is the result of checkConnection)
checkConnection is a redux thunk action:
export const checkConnection = () => async (dispatch, _, {
Intro
}) => {
dispatch(introConnectionPending())
try {
const { data: { serverTime } } = await Intro.checkConnection()
dispatch(introConnectionSuccess(serverTime))
} catch ({ message }) {
dispatch(introConnectionFailure(message))
}
}
So, now every time I dispatch an action that calls for an API the checkConnection runs first.
The problem is when the reducer responsible for type that main action dispatched (not the checkConnection) gets called it doesn't even see the payload.
Here is an example of a action:
export const getData = () => async (dispatch, getState, {
API
}) => {
dispatch(dataPending())
const credentials = getUsernamePasswordCombo(getState())
try {
const { data } = await API.login(credentials)
dispatch(dataSuccess(data))
} catch ({ message }) {
dispatch(dataFailure())
}
}
and its reducer:
export default typeToReducer({
[SET_DATA]: {
PENDING: state => ({
...state,
isPending: true
})
},
SUCCESS: (state, { payload: { data } }) => ({
...state,
isPending: false,
...data
}),
FAILURE: state => ({
...state,
isPending: false,
isError: true
})
}, initialValue)
The reducer is totally wrong. It should be:
export default typeToReducer({
[SET_DATA]: {
PENDING: state => ({
...state,
isPending: true
}),
SUCCESS: (state, { payload: { data } }) => ({
...state,
isPending: false,
...data
}),
FAILURE: state => ({
...state,
isPending: false,
isError: true
})
}
}, initialValue)
Note the SUCCESS and FAILURE parts are now inside [SET_DATA]
I was trying to reset the data, and want to go to initial state ,I know that the immutability playing major role in this part.
Below is my store data (Flow Completed data)
animalSense: {
selectedVision: 'dayLight',
selectedState: 'california',
viewedVisions: ['dayLightcalifornia', 'dayLightsouthAfrica', 'nightVisioncalifornia'],
viewedAnimals: ['dog', 'cat']
},
I want to replace it with the below data
animalSense: {
selectedVision: '',
selectedState: '',
viewedVisions: [''],
viewedAnimals: []
},
I know the below action is the Straight and proper way to add initial data is
export const RESET_ANIMAL_SENSES = 'actions/reset_animal_senses';
export default () => ({
type: RESET_ANIMAL_SENSES,
payload: {
selectedVision: '',
selectedState: '',
selectedAnimal: '',
viewedVisions: [''],
viewedAnimals: []
}
});
But the above action maintaining the same state
Below action is Working Solution but I don't know is this a Proper way
export const RESET_ANIMAL_SENSES = 'actions/reset_animal_senses';
const data = JSON.stringify({
selectedVision: '',
selectedState: '',
selectedAnimal: '',
viewedVisions: [''],
viewedAnimals: []
});
export default () => ({
type: RESET_ANIMAL_SENSES,
payload: JSON.parse(data)
});
When we are using stringify the connectivity has been ended and the new state has been added but i don't know why this is not working without JSON.stringify()?
Reducer
import { SELECT_VISION } from '../actions/select_vision_type';
import { CHANGE_ANIMAL_VIDEO_STATE } from '../actions/change_animal_video_state';
import { UPDATE_ANIMALS } from '../actions/update_animals';
import { RESET_ANIMAL_SENSES } from '../actions/reset_animal_senses';
export default (state = {}, action) => {
let newState = state;
switch (action.type) {
case SELECT_VISION:
newState = { ...state, ...action.payload };
break;
case CHANGE_ANIMAL_VIDEO_STATE:
newState = { ...state, ...action.payload };
break;
case UPDATE_ANIMALS:
newState = { ...state, ...action.payload };
break;
case RESET_ANIMAL_SENSES:
newState = { ...state, ...action.payload };
break;
default:
break;
}
return newState;
};
Spread Operator in payload Solved this issue
export const RESET_ANIMAL_SENSES = 'actions/reset_animal_senses';
const data = {
selectedVision: '',
selectedState: '',
selectedAnimal: '',
viewedVisions: [''],
viewedAnimals: []
};
export default () => ({
type: RESET_ANIMAL_SENSES,
payload: { ...data } // here is the solution
});
Try this out, I'd do good amount of refactors to your reducer.
import { SELECT_VISION } from '../actions/select_vision_type';
import { CHANGE_ANIMAL_VIDEO_STATE } from '../actions/change_animal_video_state';
import { UPDATE_ANIMALS } from '../actions/update_animals';
import { RESET_ANIMAL_SENSES } from '../actions/reset_animal_senses';
const initialState = {
selectedVision: '',
selectedState: '',
selectedAnimal: '',
viewedVisions: [''],
viewedAnimals: []
}
export default (state = initialState, action) => {
switch (action.type) {
// since all the cases have common code.
case SELECT_VISION:
case CHANGE_ANIMAL_VIDEO_STATE:
case UPDATE_ANIMALS: {
return { ...state, ...action.payload }
}
case RESET_ANIMAL_SENSES: {
return { ...initialState }
}
default: {
return state;
}
}
};
Try this reducer once. However, currently I don't have a clarity on why would it work with stringify in place.
I don´t think this issue is bound to a specific framework or library, but applies to all store based application following the action - reducer pattern.
For clarity, I am using Angular and #ngrx.
In the application I am working on we need to track the loading state of individual resources.
The way we handle other async requests is by this, hopefully familiar, pattern:
Actions
GET_RESOURCE
GET_RESOURCE_SUCCESS
GET_RESOURCE_FAILURE
Reducer
switch(action.type)
case GET_RESOURCE:
return {
...state,
isLoading = true
};
case GET_RESOURCE_SUCCESS:
case GET_RESOURCE_FAILURE:
return {
...state,
isLoading = false
};
...
This works well for async calls where we want to indicate the loading state globally in our application.
In our application we fetch some data, say BOOKS, that contains a list of references to other resources, say CHAPTERS.
If the user wants to view a CHAPTER he/she clicks the CHAPTER reference that trigger an async call. To indicate to the user that this specific CHAPTER is loading, we need something more than just a global isLoading flag in our state.
The way we have solved this is by creating a wrapping object like this:
interface AsyncObject<T> {
id: string;
status: AsyncStatus;
payload: T;
}
where AsyncStatus is an enum like this:
enum AsyncStatus {
InFlight,
Success,
Error
}
In our state we store the CHAPTERS like so:
{
chapters: {[id: string]: AsyncObject<Chapter> }
}
However, I feel like this 'clutter' the state in a way and wonder if someone has a better solution / different approach to this problem.
Questions
Are there any best practices for how to handle this scenario?
Is there a better way of handling this?
I have faced several times this kind of situation but the solution differs according to the use case.
One of the solution would be to have nested reducers. It is not an antipattern but not advised because it is hard to maintain but it depends on the usecase.
The other one would be the one I detail below.
Based on what you described, your fetched data should look like this:
[
{
id: 1,
title: 'Robinson Crusoe',
author: 'Daniel Defoe',
references: ['chp1_robincrusoe', 'chp2_robincrusoe'],
},
{
id: 2,
title: 'Gullivers Travels',
author: 'Jonathan Swift',
references: ['chp1_gulliverstravels', 'chp2_gulliverstravels', 'chp3_gulliverstravels'],
},
]
So according to your data, your reducers should look like this:
{
books: {
isFetching: false,
isInvalidated: false,
selectedBook: null,
data: {
1: { id: 1, title: 'Robinson Crusoe', author: 'Daniel Defoe' },
2: { id: 2, title: 'Gullivers Travels', author: 'Jonathan Swift' },
}
},
chapters: {
isFetching: false,
isInvalidated: true,
selectedChapter: null,
data: {
'chp1_robincrusoe': { isFetching: false, isInvalidated: true, id: 'chp1_robincrusoe', bookId: 1, data: null },
'chp2_robincrusoe': { isFetching: false, isInvalidated: true, id: 'chp2_robincrusoe', bookId: 1, data: null },
'chp1_gulliverstravels': { isFetching: false, isInvalidated: true, id: 'chp1_gulliverstravels', bookId: 2, data: null },
'chp2_gulliverstravels': { isFetching: false, isInvalidated: true, id: 'chp2_gulliverstravels', bookId: 2, data: null },
'chp3_gulliverstravels': { isFetching: false, isInvalidated: true, id: 'chp3_gulliverstravels', bookId: 2, data: null },
},
}
}
With this structure you won't need isFetching and isInvalidated in your chapter reducers as every chapter is a separated logic.
Note: I could give you a bonus details later on on how we can leverage the isFetching and isInvalidated in a different way.
Below the detailed code:
Components
BookList
import React from 'react';
import map from 'lodash/map';
class BookList extends React.Component {
componentDidMount() {
if (this.props.isInvalidated && !this.props.isFetching) {
this.props.actions.readBooks();
}
}
render() {
const {
isFetching,
isInvalidated,
data,
} = this.props;
if (isFetching || (isInvalidated && !isFetching)) return <Loading />;
return <div>{map(data, entry => <Book id={entry.id} />)}</div>;
}
}
Book
import React from 'react';
import filter from 'lodash/filter';
import { createSelector } from 'reselect';
import map from 'lodash/map';
import find from 'lodash/find';
class Book extends React.Component {
render() {
const {
dispatch,
book,
chapters,
} = this.props;
return (
<div>
<h3>{book.title} by {book.author}</h3>
<ChapterList bookId={book.id} />
</div>
);
}
}
const foundBook = createSelector(
state => state.books,
(books, { id }) => find(books, { id }),
);
const mapStateToProps = (reducers, props) => {
return {
book: foundBook(reducers, props),
};
};
export default connect(mapStateToProps)(Book);
ChapterList
import React from 'react';
import { connect } from 'react-redux';
import { createSelector } from 'reselect';
import map from 'lodash/map';
import find from 'lodash/find';
class ChapterList extends React.Component {
render() {
const { dispatch, chapters } = this.props;
return (
<div>
{map(chapters, entry => (
<Chapter
id={entry.id}
onClick={() => dispatch(actions.readChapter(entry.id))} />
))}
</div>
);
}
}
const bookChapters = createSelector(
state => state.chapters,
(chapters, bookId) => find(chapters, { bookId }),
);
const mapStateToProps = (reducers, props) => {
return {
chapters: bookChapters(reducers, props),
};
};
export default connect(mapStateToProps)(ChapterList);
Chapter
import React from 'react';
import { connect } from 'react-redux';
import { createSelector } from 'reselect';
import map from 'lodash/map';
import find from 'lodash/find';
class Chapter extends React.Component {
render() {
const { chapter, onClick } = this.props;
if (chapter.isFetching || (chapter.isInvalidated && !chapter.isFetching)) return <div>{chapter.id}</div>;
return (
<div>
<h4>{chapter.id}<h4>
<div>{chapter.data.details}</div>
</div>
);
}
}
const foundChapter = createSelector(
state => state.chapters,
(chapters, { id }) => find(chapters, { id }),
);
const mapStateToProps = (reducers, props) => {
return {
chapter: foundChapter(reducers, props),
};
};
export default connect(mapStateToProps)(Chapter);
Book Actions
export function readBooks() {
return (dispatch, getState, api) => {
dispatch({ type: 'readBooks' });
return fetch({}) // Your fetch here
.then(result => dispatch(setBooks(result)))
.catch(error => dispatch(addBookError(error)));
};
}
export function setBooks(data) {
return {
type: 'setBooks',
data,
};
}
export function addBookError(error) {
return {
type: 'addBookError',
error,
};
}
Chapter Actions
export function readChapter(id) {
return (dispatch, getState, api) => {
dispatch({ type: 'readChapter' });
return fetch({}) // Your fetch here - place the chapter id
.then(result => dispatch(setChapter(result)))
.catch(error => dispatch(addChapterError(error)));
};
}
export function setChapter(data) {
return {
type: 'setChapter',
data,
};
}
export function addChapterError(error) {
return {
type: 'addChapterError',
error,
};
}
Book Reducers
import reduce from 'lodash/reduce';
import { combineReducers } from 'redux';
export default combineReducers({
isInvalidated,
isFetching,
items,
errors,
});
function isInvalidated(state = true, action) {
switch (action.type) {
case 'invalidateBooks':
return true;
case 'setBooks':
return false;
default:
return state;
}
}
function isFetching(state = false, action) {
switch (action.type) {
case 'readBooks':
return true;
case 'setBooks':
return false;
default:
return state;
}
}
function items(state = {}, action) {
switch (action.type) {
case 'readBook': {
if (action.id && !state[action.id]) {
return {
...state,
[action.id]: book(undefined, action),
};
}
return state;
}
case 'setBooks':
return {
...state,
...reduce(action.data, (result, value, key) => ({
...result,
[key]: books(value, action),
}), {});
},
default:
return state;
}
}
function book(state = {
isFetching: false,
isInvalidated: true,
id: null,
errors: [],
}, action) {
switch (action.type) {
case 'readBooks':
return { ...state, isFetching: true };
case 'setBooks':
return {
...state,
isInvalidated: false,
isFetching: false,
errors: [],
};
default:
return state;
}
}
function errors(state = [], action) {
switch (action.type) {
case 'addBooksError':
return [
...state,
action.error,
];
case 'setBooks':
case 'setBooks':
return state.length > 0 ? [] : state;
default:
return state;
}
}
Chapter Reducers
Pay extra attention on setBooks which will init the chapters in your reducers.
import reduce from 'lodash/reduce';
import { combineReducers } from 'redux';
const defaultState = {
isFetching: false,
isInvalidated: true,
id: null,
errors: [],
};
export default combineReducers({
isInvalidated,
isFetching,
items,
errors,
});
function isInvalidated(state = true, action) {
switch (action.type) {
case 'invalidateChapters':
return true;
case 'setChapters':
return false;
default:
return state;
}
}
function isFetching(state = false, action) {
switch (action.type) {
case 'readChapters':
return true;
case 'setChapters':
return false;
default:
return state;
}
}
function items(state = {}, action) {
switch (action.type) {
case 'setBooks':
return {
...state,
...reduce(action.data, (result, value, key) => ({
...result,
...reduce(value.references, (res, chapterKey) => ({
...res,
[chapterKey]: chapter({ ...defaultState, id: chapterKey, bookId: value.id }, action),
}), {}),
}), {});
};
case 'readChapter': {
if (action.id && !state[action.id]) {
return {
...state,
[action.id]: book(undefined, action),
};
}
return state;
}
case 'setChapters':
return {
...state,
...reduce(action.data, (result, value, key) => ({
...result,
[key]: chapter(value, action),
}), {});
},
default:
return state;
}
}
function chapter(state = { ...defaultState }, action) {
switch (action.type) {
case 'readChapters':
return { ...state, isFetching: true };
case 'setChapters':
return {
...state,
isInvalidated: false,
isFetching: false,
errors: [],
};
default:
return state;
}
}
function errors(state = [], action) {
switch (action.type) {
case 'addChaptersError':
return [
...state,
action.error,
];
case 'setChapters':
case 'setChapters':
return state.length > 0 ? [] : state;
default:
return state;
}
}
Hope it helps.