Is it a best practice to write conditions in action creators ? if not what are the alternative for that?
my scenario is that , i have a file uploader and depending a selection i either push the data to reducerA or reducerB.
return function (dispatch, getState) {
const { selectedStage } = getState();
if (selectedStage.stage === Constants.STAGE_CARRIER) {
**dispatch(uploadCarrier(payload));**
} else {
**dispatch(uploadWeb(payload));**
}
};
Related
How to handle firebase auth state observer in redux saga?
firebase.auth().onAuthStateChanged((user) => {
});
I want to run APP_START saga when my app starts which will run firebase.auth().onAuthStateChanged observer and will run other sagas depending on the callback.
As I understand eventChannel is right way to do it. But I don't understand how to make it work with firebase.auth().onAuthStateChanged.
Can someone show how to put firebase.auth().onAuthStateChanged in to eventChannel?
You can use eventChannel. Here is an example code:
function getAuthChannel() {
if (!this.authChannel) {
this.authChannel = eventChannel(emit => {
const unsubscribe = firebase.auth().onAuthStateChanged(user => emit({ user }));
return unsubscribe;
});
}
return this.authChannel;
}
function* watchForFirebaseAuth() {
...
// This is where you wait for a callback from firebase
const channel = yield call(getAuthChannel);
const result = yield take(channel);
// result is what you pass to the emit function. In this case, it's an object like { user: { name: 'xyz' } }
...
}
When you are done, you can close the channel using this.authChannel.close().
Create your own function onAuthStateChanged() that will return a Promise
function onAuthStateChanged() {
return new Promise((resolve, reject) => {
firebase.auth().onAuthStateChanged((user) => {
if (user) {
resolve(user);
} else {
reject(new Error('Ops!'));
}
});
});
}
Then use call method to get the user synchronously
const user = yield call(onAuthStateChanged);
This could be handled in the Saga such as the following for Redux Saga Firebase:
// Redux Saga: Firebase Auth Channel
export function* firebaseAuthChannelSaga() {
try {
// Auth Channel (Events Emit On Login And Logout)
const authChannel = yield call(reduxSagaFirebase.auth.channel);
while (true) {
const { user } = yield take(authChannel);
// Check If User Exists
if (user) {
// Redux: Login Success
yield put(loginSuccess(user));
}
else {
// Redux: Logout Success
yield put(logoutSuccess());
}
}
}
catch (error) {
console.log(error);
}
};
here is how you would run the onAuthStateChanged observable using redux-saga features (mainly eventChannel)
import { eventChannel } from "redux-saga";
import { take, call } from "redux-saga/effects";
const authStateChannel = function () {
return eventChannel((emit) => {
const unsubscribe = firebase.auth().onAuthStateChanged(
(doc) => emit({ doc }),
(error) => emit({ error })
);
return unsubscribe;
});
};
export const onAuthStateChanged = function* () {
const channel = yield call(authStateChannel);
while (true) {
const { doc, error } = yield take(channel);
if (error) {
// handle error
} else {
if (doc) {
// user has signed in, use `doc.toJSON()` to check
} else {
// user has signed out
}
}
}
};
please note that other solutions that don't utilize channel sagas are not optimal for redux-saga, because turning an observable into a promise is not a valid solution in this case since you would need to call the promise each time you anticipate a change in authentication state (like for example: taking every USER_SIGNED_IN action and calling the "promisified" observable), which will negate the whole purpose of an observable
I am working on a web app built on react + redux + thunk.
I have action creators as below. There are 2 async API calls, first fetchUser() will get user related info from the server, then fetchUserComments is another async call which returns me all the user comments.
export function fetchUserInfoFlow () {
return (dispatch, getState) => {
return dispatch(fetchUser()).then(() => {
return dispatch(fetchUserComments()
})
}
}
export function fetchUser() {
return (dispatch, getState) => {
return axios.get('urlhere')
.then(function (response) {
// basically fetch user data and update the store
dispatch({type: FETCH_USERS, user:response.data)
})
.catch(function (error) {
console.error(error)
})
}
}
export function fetchUserComment() {
return (dispatch, getState) => {
return axios.get('urlhere')
.then(function (response) {
// fetch user comments, get the user list from store, matching the user id and append the comments list to the user
let user = {...getState().user}
response.data.forEach(function (userComment) {
user.forEach(function (userComment) {
if(user.userId = userComment.userId){
user.comments = userComment.comments
}
}
}
dispatch({type: UPDATE_USER_COMMENT, user:response.data)
})
.catch(function (error) {
console.error(error)
})
}
}
I have several action creators similar to the above fetching user's related info and finally updating modifying the store's user list.
The problem is that the component does not re-render when the state updated, suspect if I have mutated the user list somewhere.
And I have read several articles that using getSate() in action creator should be only used in several cases and should not update its values as this will mutates the state.
In this cases, where should I put the logic of modifying the user list and how to avoid mutating the user list?
Thanks a lot!
This part should just go into your reducer, since thats the only place you should be making changes to the state:
let user = {...getState().user}
response.data.forEach(function (userComment) {
user.forEach(function (userComment) {
if(user.userId = userComment.userId){
user.comments = userComment.comments //mutating state
}
}
}
I have created a thunk that dispatches a bunch of different actions:
export function resetEverything() {
return function (dispatch) {
return Promise.all([
dispatch(updateCurrentColor('blue')),
dispatch(updateCurrentTypeChoice('hot')),
dispatch(updateData('fish', {})),
dispatch(updateData('giraffes', {})),
dispatch(updateData('elephants', {})),
dispatch(updateData('zebras', {})),
]).then(() => console.log('resetEverything called'));
};
}
These actions are also used in the application individually. Individually called, they work fine; the store is updated with the payloads.
However, in this batch operation, all of the actions are dispatched, the console shows "resetEverything called", and even when I look through the Redux extension in Chrome, each of the actions are dispatched with the same structure (with different payload, naturally). But...when I look at the Diff it says (states are equal) and sure enough, examining the State>Tree shows that the store keys haven't been updated at all.
Why isn't this working? Why are the dispatched actions being ignored?
Reducer:
import update from 'immutability-helper';
function reducer(state = initialState, action = {}) {
switch (action.type) {
case UPDATE_CURRENT_COLOR:
return update(state, { currentColor: { $set: action.payload } });
case UPDATE_CURRENT_TYPE_CHOICE:
return update(state, { currentTypeChoice: { $set: action.payload } });
case UPDATE_DATA:
return update(state, { data: { [action.payload.property]: { $merge: action.payload.dataObject } } });
default: return state;
}
}
Recently I've been looking into react and redux. I read up the official documentation and tried some ToDo List tutorials. Part 1 is just about react and this is part 2 about redux:
http://www.theodo.fr/blog/2016/03/getting-started-with-react-redux-and-immutable-a-test-driven-tutorial-part-2/
So basically he just sets up a store and initially adds an array of a few todos. Now I don't want my data to be local and I want to fetch it from an API. I'm having a hard time understanding how this actually works. So the code I would use in my action_creators.js is:
export function fetchData() {
return dispatch => {
fetch('http://127.0.0.1:8000/example')
.then(res => res.json())
.then(res => dispatch({
type: FETCH_DATA,
data: res
}))
}
}
Now in the example code for example adding a 'todo':
export function addItem(text) {
return {
type: 'ADD_ITEM',
text
}
}
You aren't dispatching anything, the tutorial does this in the reducer? But when you return dispatch your fetch, does this automatically get dispatched to your store?
If so I have no clue what I should write in my reducer ..
This is the code I have for adding a 'todo':
import {Map} from 'immutable';
function setState(state, newState) {
return state.merge(newState);
}
function fetchData(state) {
return state;
}
function addItem(state, text) {
const itemId = state.get('hostnames').reduce((maxId, item) => Math.max(maxId,item.get('id')), 0) + 1;
const newItem = Map({id: itemId, text: text, status: 'active'});
return state.update('hostnames', (hostnames) => hostnames.push(newItem));
}
export default function(state = Map(), action) {
switch (action.type) {
case 'SET_STATE':
return setState(state, action.state);
case 'ADD_ITEM':
return addItem(state, action.text);
case 'FETCH_DATA':
return fetchData(state);
}
return state;
}
So basically my question is, how do I fetch the data ( if the fetch is wrong now ) and how do I add the fetched data from my api to the store in my reducer.
I just find react and redux pretty complicated so sorry if I'm asking a really noob question or just making big mistakes in the way I want to do something.
Thanks in advance for any help.
imagine your json
{
"data": {
"apple": 1,
"banana": 3,
},
"status": 200,
}
your actions
export function fetchData() {
return dispatch => {
fetch('http://127.0.0.1:8000/example')
.then(res => res.json())
.then((responseData) => {
if(responseData.status === 200){
dispatch(setData(responseData));
}
})
}
}
export function setData(responseData) {
return {type: SET_DATA, data: responseData.data }
}
your reducer
const initialState = { data: null };
export default function(state = initialState, action) {
switch (action.type) {
case 'SET_DATA':
return Object.assign({}, state, {
data: action.data,
})
default:
return state;
}
}
then your state will become
{ data: {
apple: 1,
banana: 3,
}
}
Actually, all your reducers should be pretty dumb and pure (without any side effects). So their only concern is to modify the state and nothing else. Fetching data from the server or any kind of orchestration should be implemented in redux middleware. Look at redux-thunk or redux-saga if you need something more complicated. Hope that helps.
I'm trying to build a simple app to view photos posted from nasa's picture of the day service (https://api.nasa.gov/api.html#apod). Currently watching for keypresses, and then changing the date (and asynchronously the picture) based on the keypress being an arrow left, up, right, or down. These would correspondingly change the date represented by a week or a day (imagine moving across a calendar one square at a time).
What I'm having trouble with is this: I've created an async action creator to fetch the next potential date - however I need to know the current state of the application and the keypress to retrieve the new date. Is there a way to encapsulate this into the action creator? Or should I put the application state where the exported action creator is called in the application so I can keep my action creator unaware of the state of the application? I've tried to do this by binding the keydown function in componentDidMount for the top level Component, but the binding to the application store doesn't seem to reflect the changes that happen in the reducer.
The async logic relying on redux-thunk middleware and q:
// This function needs to know the current state of the application
// I don't seem to be able to pass in a valid representation of the current state
function goGetAPIUrl(date) {
...
}
function getAsync(date) {
return function (dispatch) {
return goGetAPIUrl(date).then(
val => dispatch(gotURL(val)),
error => dispatch(apologize(error))
);
};
}
export default function eventuallyGetAsync(event, date) {
if(event.which == 37...) {
return getAsync(date);
} else {
return {
type: "NOACTION"
}
}
}
Here's the top level binding to the gridAppState, and other stuff that happens at top level that may be relevant that I don't quite understand.
class App extends React.Component {
componentDidMount() {
const { gridAppState, actions } = this.props;
document.addEventListener("keydown", function() {
actions.eventuallyGetAsync(event, gridAppState.date);
});
}
render() {
const { gridAppState, actions } = this.props;
return (
<GridApp gridAppState={gridAppState} actions={actions} />
);
}
}
App.propTypes = {
actions: PropTypes.object.isRequired,
gridAppState: PropTypes.object.isRequired
};
function mapStateToProps(state) {
return {
gridAppState: state.gridAppState
};
}
function mapDispatchToProps(dispatch) {
return {
actions: bindActionCreators(GridActions, dispatch)
};
}
export default connect(
mapStateToProps,
mapDispatchToProps
)(App);
I've validated that the correctly modified date object is getting to the reducer - however the gridAppState seems stuck at my initial date that is loaded.
What is the right way to approach async logic in redux that relies on attaching event handlers and current application state? Is there a right way to do all three?
You should handle the event in your component and call the correct action depending on the key pressed.
So when you dispatch an async action you can do something like
export default function getNextPhoto(currentDate) {
return (dispatch) => {
const newDate = calculateNewDate(currentDate);
dispatch(requestNewPhoto(newDate));
return photosService.getPhotoOfDate(newDate)
.then((response) => {
dispatch(newPhotoReceived(response.photoURL);
});
};
}
You should handle the keypress event on the component and just dispatch your action when you know you need to fetch a new photo.
Your App would look like
class App extends React.Component {
componentDidMount() {
const { gridAppState, actions } = this.props;
document.addEventListener("keydown", function() {
if (event.which == 37) {
actions.getNextPhoto(gridAppState.date);
} else if (...) {
actions.getPrevPhoto(gridAppState.date);
}
// etc
});
}
}
By the way you re still missing your reducers that update your state in the Redux Store.