When I dispatch an action after dispatching another action, I noticed that my state isFetching becomes undefined. I think it's probably some asynchronous issue with the actions dispatching after the other. How would I fix this so that I can get both actions to dispatch correctly?
My redux module:
const FETCHING = 'FETCHING'
const FETCHING_KEYWORD = 'FETCHING_KEYWORD'
function fetching() {
return {
type: FETCHING,
}
}
function settingKeyWord(keyWord) {
return {
type: FETCHING_KEYWORD,
keyWord,
}
}
export function fetchKeyWord (keyWord) {
return (dispatch, getState) => {
const { isFetching } = getState()
const { keyWord } = getState()
// After I dispatch the two actions here, isFetching becomes undefined
dispatch(fetching())
dispatch(settingKeyWord(keyWord))
}
}
const initialState = {
isFetching: false,
keyWord: '',
}
export default function results(state = initialState, action) {
switch (action.type) {
case FETCHING:
return {
isFetching: true,
}
case FETCHING_KEYWORD:
return {
keyWord: action.keyWord,
}
default:
return state
}
}
The reducer cases need to return the entire state, not just the updated part, so the problem should also occur when dispatching either action normally. You can fix it by using Object.assign or object-spread syntax in the reducer cases. For example, for Fetching:
case FETCHING:
return Object.assign((), state, {
isFetching: true,
})
or
case FETCHING:
return {...state,
isFetching: true,
})
Related
In order to decrease code duplication in the redux-related part of my app, I have come up with reducer factories in order to group repetative logic into an abstract reducer which is then turned into concrete reducer instances by passing name param to the factory.
ReduxFactory/reducer.js
const initialState = {
foo: null
}
function reducerFactory(name = '') {
return function reducer(state = initialState, action) {
switch (action.type) {
case `${name}_DO_SOMETHING`: {
return state
}
default:
return state;
}
}
}
export default reducerFactory;
Then I have two modules for which I build instances of a reducer factory:
fileA.js
import reducerFactory from './ReduxFactory/reducer'
const reducer = reducerFactory('OBJECT_A')
fileB.js
import reducerFactory from './ReduxFactory/reducer'
const reducer = reducerFactory('OBJECT_B')
Now imagine that on objects of type B I need to implement some ad-hoc functionality, which I do not want to include into the general reducer factory body because it is too specialized. Is there any valid JS code pattern to implement this ?
If I understand you correctly I think you can do the following:
function reducerFactory(name = '', extras = (x) => x) {
return function reducer(state = initialState, action) {
switch (action.type) {
case `${name}_DO_SOMETHING`: {
return state;
}
default:
return extras(state, action);
}
};
}
const reducer = reducerFactory(
'OBJECT_B',
(state, action) => {
if (action.type === 'extra') {
//return changed state
}
return state;
}
);
I am just trying to run a simple redux program when i use command node index it shows me error that action must be plain objects below is my code for that
const redux = require('redux')
const createStore = redux.createStore
const BUY_CAKE = 'BUY_CAKE'
function buyCake () {
return
{
type: BUY_CAKE
}
}
const initialState = {
numOfCakes: 10
}
const reducer = (state = initialState, action) => {
switch (action.type) {
case BUY_CAKE: return {
...state,
numOfCakes: state.numOfCakes - 1
}
default: return state
}
}
const store = createStore(reducer)
console.log("initial state is ", store.getState())
const unsubscribe = store.subscribe(() => console.log("updated", store.getState()))
store.dispatch(buyCake())
store.dispatch(buyCake())
store.dispatch(buyCake())
store.dispatch(buyCake())
unsubscribe()
when i dispatch(buyCake()) then only it shows error but if i do store.dispatch({type:BUY_CAKE}) then code runs fine why is the error occuring
Because your return statement is wrongly formatted. Be aware of this deadly feature:
JavaScript will automatically insert semicolons. Without the parentheses, JavaScript would ignore the following lines and return without a value.
This is your function with semicolons, which will return undefined:
function buyCake(){
return;
{
type:BUY_CAKE
};
};
Solution: Move your curly brackets to the return line:
function buyCake(){
return {
type: BUY_CAKE
}
}
Below are my action and reducer files - In my component state I am only seeing this.props.mainData - but others subdataOneData etc., are not being loaded in to the state - till reducer i see the right actions are being dispatched and I also see the data for sub - calls - but they are not reaching my component - I have mapStatetoprops - where I am doing
New issue: as per the updated code - when i print out payload in reducer - I see maindata with the api data but SubData [{}, {}, {}] ..?
Updated code:
import { GET_DATA_AND_SUBDATA } from '../constants/types';
export function getMainData() {
return async function getMainData(dispatch) {
const { data } = await getMainDataAPI();
const subData = data.map((item) => {
const endpoint = 'build with item.name';
return Request.get(endpoint);
});
console.log('subddd' + subData); prints -> **[object Promise],[object Promise],[object Promise]**
dispatch({
type: GET_DATA_AND_SUBDATA,
payload: { data, subData }
});
};
}
async function getMainDataAPI() {
const endpoint = 'url';
return Request.get(endpoint);
}
The problem lies on the way you dispatch the actions.
You are not providing data for mainData and subdataOneData at the same time.
export function getData() {
return async function getData(dispatch) {
const { data } = await getDataAPI();
// This will cause first re-render
dispatch({ type: GET_DATA, payload: data });
Object.keys(data).map((keyName, keyIndex) => {
const endpoint = 'ENDPOINT';
Request.get(endpoint).then((response) => {
// This will cause second re-render
dispatch({
type: GET_subdata + keyIndex,
payload: response.data });
});
return keyIndex;
});
};
}
At first render your subdataOneData is not availble yet.
You are not even specifying a default value in the reducer, therefore it will be undefined.
You can change your action thunk like this
export function getData() {
return async function getData(dispatch) {
const { data } = await getDataAPI();
const subDataResponse = await Promise.all(
Object.keys(data).map( () => {
const endpoint = 'ENDPOINT';
return Request.get(endpoint)
})
)
const subData = subDataResponse.map( response => response.data )
dispatch({
type: GET_DATA_AND_SUBDATA
payload: { data, subData }
});
};
}
And change your reducer accordingly in order to set all data at once.
export default function myReducer(state = {}, action) {
switch (action.type) {
case GET_DATA_AND_SUBDATA:
return {
...state,
mainData: action.payload.data,
subdataOneData: action.payload.subData[0],
subdataTwoData: action.payload.subData[1]
};
default:
return state;
}
}
Note: it's also a good practice to set your initial state in the reducer.
const initialState = {
mainData: // SET YOUR INITIAL DATA
subdataOneData: // SET YOUR INITIAL DATA
subdataTwoData: // SET YOUR INITIAL DATA
}
export default function myReducer(initialState, action) {
I created a rootSaga in sagas.js as
function* fetchStuff(action) {
try {
yield put({type: 'INCREMENT'})
yield call(delay, 1000)
yield put({type: 'DECREMENT'})
const highlights = yield call(API.getStuff, action.data.myObject);
} catch (e) {
yield put({type: 'FETCH_STUFF_FAILED', message: e});
}
}
export default function* rootSaga() {
yield takeEvery('INIT_LOAD', fetchStuff);
}
I am calling the INIT_LOAD after thirdParty.method:
class myClass extends Component {
constructor(props) {
super(props);
}
componentDidMount() {
this.load();
}
load = () => {
this.init = () => {
this.myObject = thirdParty.method(event => {
const action = {
type: 'INIT_LOAD',
payload: {
myObject: this.myObject
}
};
store.dispatch(action);
});
};
this.init();
};
render() {
return (
<div id="render-here" />
);
}
Passing the this.myObject in the action that is dispatched does not trigger the saga. If I change the action payload to a string, like the following, the saga is triggered.
const action = {
type: 'INIT_LOAD',
payload: {
myObject: 'this.myObject'
}
};
Why am I unable to pass this.myObject but a string is ok?
UPDATE: It is not a saga issue. I replicated the same issue with just plain redux. The rootReducer as
export default function rootReducer(state = initialState, action) {
switch (action.type) {
case 'INIT_LOAD':
return Object.assign({}, state, { myObject: action.payload.myObject });
default:
return state;
}
}
As I mentioned in the comment below, assigning it to an object Obj does not change the issue
let Obj = {};
...
load = () => {
this.init = () => {
Obj.myObject = thirdParty.method(event => {
const action = {
type: 'INIT_LOAD',
payload: {
myObj: Obj
}
};
store.dispatch(action);
});
};
this.init();
};
UPDATE2
I cleaned the code up & simply dispatched an action in the component that triggers the saga. Inside the saga is where I do the init(). I ran into another issue where the object that I was trying to save in the redux store has active socket sessions (which were given me cross-domain issues). Although I didn't solve my original problem, not storing a socket object made my problem go away.
My question relates to redux and more specifically how to handle errors/failures from within reducer functions. I am in reference to the ngrx example app (https://github.com/ngrx/example-app) and the way it handle errors/failures.
Here is the reducer function I am referring to:
export function reducer(state = initialState, action: collection.Actions): State {
switch (action.type) {
case collection.ActionTypes.LOAD: {
return Object.assign({}, state, {
loading: true
});
}
case collection.ActionTypes.LOAD_SUCCESS: {
const books = action.payload;
return {
loaded: true,
loading: false,
ids: books.map(book => book.id)
};
}
case collection.ActionTypes.ADD_BOOK_SUCCESS:
case collection.ActionTypes.REMOVE_BOOK_FAIL: {
const book = action.payload;
if (state.ids.indexOf(book.id) > -1) {
return state;
}
return Object.assign({}, state, {
ids: [ ...state.ids, book.id ]
});
}
case collection.ActionTypes.REMOVE_BOOK_SUCCESS:
case collection.ActionTypes.ADD_BOOK_FAIL: {
const book = action.payload;
return Object.assign({}, state, {
ids: state.ids.filter(id => id !== book.id)
});
}
default: {
return state;
}
}
}
Can someone please explain the necessity for dealing with those two actions from within the reducer function:
REMOVE_BOOK_FAIL
ADD_BOOK_FAIL
For instance why remove the book from the state (in the case of the ADD_BOOK_FAIL action)?
If the add book action has failed, then the book is not present in the store. Is it?
Maybe it's the naming used that makes it a red herring, my guess is that ADD_BOOK_FAIL could be in use somewhere else for a different use case as a fall back mechanism.
I agree the way you describe it this doesnt make sense the developer did it for this reason.