I would like to create some middleware to check a tokens expires_at field refreshing the token if necessary and updating the state for the token fields.
I have used the redux toolkit to create the redux functionality, making use of slices. I have a slice that will update the state with token data and this works on the callback for the initial token.
When creating the middleware I can not get the slice to be called and therefore the state remains unchanged.
As a simple spike without an api call:
import { useSelector, useDispatch } from 'react-redux';
import { setTokens } from '../features/tokens/tokenSlice';
const refresher = () => ({ dispatch, getState }) => (next) => (action) => {
const exp_at = useSelector((state) => state.tokens.expires_at);
if(hasBreachedThreshold(exp_at)){
dispatch = useDispatch();
dispatch(
setTokens({
access_token: 'new token',
expires_at: 637423776000000000, -- hard coded date way in the future.
})
}
... else carry on.
);
I would expect when the middleware is called, on the first pass hasBreachedThreshold() returns true and the dispatch method would call the slice reducer and update the state. Any further runs would pass over as hasBreachedThreshold() would return false - for a while anyway.
What is happening though is that the hasBreachThreshold always returns false because the state is never updated, causing an indefinite loop.
The middleware is configured correctly and is called.
The expires_at value is extracted from the state.
hasBreachThreshold() is tested thoroughly and behaves correctly.
Being fairly new to React / Redux I expect my understanding of how and when to use dispatch is wrong. I assumed I could use dispatch similarly to how I do in my components, is this not the case? or am I going about this totally the wrong way?
When writing a middleware you have already the dispatch function and Redux store available through the function params:
// Use `dispatch` & `getState`
const refresher = () => ({ dispatch, getState }) => (next) => (action) => {
const exp_at = getState().tokens.expires_at;
if(hasBreachedThreshold(exp_at)){
dispatch(
setTokens({
access_token: 'new token',
expires_at: 637423776000000000, -- hard coded date way in the future.
})
}
);
Also you have essential mistake of when to use React hooks, refer to Rules of Hooks.
Hooks are not available in context of Redux middleware.
Related
I'm using RTK (Redux Toolkit) and RTK Query to manage my store and API requests.
To catch errors globally, I followed this example. That works fine, but now I'd like to log out the user when a request was rejected because of a 401 - Unauthorized-error.
const rtkQueryErrorLogger = api => next => action => {
if (isRejectedWithValue(action)) {
if (action.payload.status === 401) {
// Reset the store (not working)
const dispatch = useDispatch();
const dipatch(logout());
// Forward to login-screen (not working)
const navigation = useNavigation();
navigation.push('Login');
}
}
return next(action);
};
Any idea? Thanks in advance!
A Redux middleware always gets a "mini-store API" object as the argument to the outermost function, which contains {dispatch, getState}:
https://redux.js.org/tutorials/fundamentals/part-4-store#writing-custom-middleware
In this case, it's the variable named api in your example.
You can access dispatch from that object and dispatch an action at any time inside your middleware. Just delete the const dispatch = useDispatch line, and either change the next line to api.dispatch() or destructure dispatch from the api object in the declaration.
Say I have a action creator function like the one below:
import {v4 as uuidv4} from uuid;
export const doSomething = (task) => (dispatch) => {
dispatch({
const id = uuidv4();
dispatch({
type: "SET_TASK",
payload: {id, task}
})
})
}
What is the logic behind having to wrap it in a dispatch method when I am calling it to update the state of a store in another action creator function?
i.e.:
import {setAlert} from "./doSomething"
// another action creator
export const anotherActionCreator = () => dispatch => {
...
dispatch(doSomething("Laundry"));
...
}
When I remove the dispatch method wrapping, it would not call the reducer and update the state in the redux store. I am thinking the action is somehow not connected to the store, but I don't understand how. I thought when you call doSomething("Laundry"), the dispatch inside it will already update the store -- but somehow it didn't -- why is that?
By default, the Redux store only understands how to accept plain action objects passed to dispatch, like:
store.dispatch({type: "todos/todoAdded", payload: "Buy milk"};
If you pass a function to dispatch(), the store will throw an error.
However, middleware wrap up the dispatch function, and can intercept whatever's been passed in to dispatch(). This allows middleware to "teach the store how to accept non-action values", such as passing a function to dispatch(someFunction).
This is how the redux-thunk middleware works. It looks for anything that is actually a function instead of an action object, intercepts that function, and calls it.
I am trying to load data when my component loads using componentDidMount. However calling the Redux action, making the call with axios seems to freeze the UI. When I have a form with 12 inputs and one makes an API call I would assume I can type in the other inputs and not have them freeze up on me.
I've tried reading some other posts on the subject but they are all a little different and everything I have tried doesn't seem to resolve the issue.
I am working on linux using React 16.8 (when using RN I use 55.4)
I have tried making my componentDidMount async as well as the redux-thunk action. It didn't seem to help anything, so I must be doing something wrong.
I tried doing the following with no success. Just using short form for what I tried. Actual code listed below.
async componentDidMount() {
await getTasks().then();
}
And I tried this
export const getTasks = () => (async (dispatch, getState) => {
return await axios.get(`${URL}`, AJAX_CONFIG).then();
}
Current Code:
Component.js
componentDidMount() {
const { userIntegrationSettings, getTasks } = this.props;
// Sync our list of external API tasks
if (!isEmpty(userIntegrationSettings)) {
getTasks(userIntegrationSettings.token)
// After we fetch our data from the API create a mapping we can use
.then((tasks) => {
Object.entries(tasks).forEach(([key, value]) => {
Object.assign(taskIdMapping, { [value.taskIdHuman]: key });
});
});
}
}
Action.js
export const getTasks = () => ((dispatch, getState) => {
const state = getState();
const { token } = state.integrations;
const URL = `${BASE_URL}/issues?fields=id,idReadable,summary,description`;
const AJAX_CONFIG = getAjaxHeaders(token);
dispatch(setIsFetchingTasks(true));
return axios.get(`${URL}`, AJAX_CONFIG)
.then((response) => {
if (!isEmpty(response.data)) {
response.data.forEach((task) => {
dispatch(addTask(task));
});
return response.data;
} else {
dispatch(setIsFetchingTasks(false));
}
})
.catch((error) => {
dispatch(setIsFetchingTasks(false));
errorConsoleDump(error);
errorHandler(error);
});
});
reducer.js
export default (state = defaultState, action) => {
switch (action.type) {
case ADD_TASK:
case UPDATE_TASK:
return update(state, {
byTaskId: { $merge: action.task },
isFetching: { $set: false }
});
default:
return state;
}
};
So in my answer what are you going to learn?
General data loading with Redux
Setting up a component lifecycle method such as componentDidMount()
Calling an action creator from componentDidMount()
Action creators run code to make an API request
API responding with data
Action creator returns an action with the fetched data on the payload property
Okay, so we know there are two ways to initialize state in a Reactjs application, we can either invoke a constructor(props) function or we can invoke component lifecycle methods. In this case, we are doing component lifecycle methods in what we can assume is a class-based function.
So instead of this:
async componentDidMount() {
await getTasks().then();
}
try this:
componentDidMount() {
this.props.fetchTasks();
}
So the action creators (fetchTasks()) state value becomes the components this.props.fetchTasks(). So we do call action creators from componentDidMount(), but not typically the way you were doing it.
The asynchronous operation is taking place inside of your action creator, not your componentDidMount() lifecycle method. The purpose of your componentDidMount() lifecycle method is to kick that action creator into action upon booting up the application.
So typically, components are generally responsible for fetching data via calling the action creator, but it's the action creator that makes the API request, so there is where you are having an asynchronous JavaScript operation taking place and it's there where you are going to be implementing ES7 async/await syntax.
So in other words it's not the component lifecycle method initiating the data fetching process, that is up to the action creator. The component lifecycle method is just calling the action creator that is initiating the data fetching process a.k.a. the asynchronous request.
To be clear, you are able to call this.props.fetchTasks() from your componentDidMount() lifecycle method after you have imported the action creator to your component like and you have imported the connect function like so:
import React from "react";
import { connect } from "react-redux";
import { fetchTasks } from "../actions";
You never provided the name of the component you are doing all this in, but at the bottom of that file you would need to do export default connect(null, { fetchTasks })(ComponentName)
I left the first argument as null because you have to pass mapStateToProps, but since I don't know if you have any, you can just pass null for now.
Instead of this:
export const getTasks = () => (async (dispatch, getState) => {
return await axios.get(`${URL}`, AJAX_CONFIG).then();
}
try this:
export const fetchTasks = () => async dispatch => {
const response = await axios.get(`${URL}`, AJAX_CONFIG);
dispatch({ type: "FETCH_TASKS", payload: response.data });
};
There is no need to define getState in your action creator if you are not going to be making use of it. You were also missing the dispatch() method which you need when developing asynchronous action creators. The dispatch() method is going to dispatch that action and send it off to all the different reducers inside your app.
This is also where middleware such as Redux-Thunk comes into play since action creators are unable to process asynchronous requests out of the box.
You did not show how you wired up your redux-thunk, but it typically goes in your your root index.js file and it looks like this:
import React from "react";
import ReactDOM from "react-dom";
import "./index.scss";
import { Provider } from "react-redux";
import { createStore, applyMiddleware } from "redux";
import thunk from "redux-thunk";
import App from "./components/App";
import reducers from "./reducers";
const store = createStore(reducers, applyMiddleware(thunk));
ReactDOM.render(
<Provider store={store}>
<App />
</Provider>,
document.querySelector("#root")
Remember that connect function I said you needed to implement? That came into being as a result of implementing or you should have implemented the Provider tag. With the Provider tag, your components can all have access to the Redux store, but in order to hook up the data to your components you will need to import the connect function.
The connect function is what reaches back up to the Provider and tells it that it wants to get access to that data inside whatever component you have that lifecycle method in.
Redux-Thunk is most definitely what you needed to implement if you have corrected everything as I have suggested above.
Why is Redux-Thunk necessary?
It does not have anything intrinsically built into it, it's just an all-purpose middleware. One thing that it does is allow us to handle action creators which is what you need it to be doing for you.
Typically an action creator returns an action object, but with redux-thunk, the action creator can return an action object or a function.
If you return an action object it must still have a type property as you saw in my code example above and it can optionally have a payload property as well.
Redux-Thunk allows you to return either an action or function within your action creator.
But why is this important? Who cares if it returns an action object or a function? What does it matter?
That's getting back to the topic of Asynchronous JavaScript and how middlewares in Redux solves the fact that Redux is unable to process asynchronous JavaScript out of the box.
So a synchronous action creator instantly returns an action with data ready to go. However, when we are working with asynchronous action creators such as in this case, it takes some amount of time for it to get its data ready to go.
So any action creator that makes an network request qualifies as an asynchronous action creator.
Network requests with JavaScript are asynchronous in nature.
So Redux-Thunk, being a middleware which is a JavaScript function that is going to be called with every single action that you dispatch. The middleware can stop the action from proceeding to your reducers, modify the action and so on.
You setup dispatch(setIsFetchingTasks(true)) but when axios returns you never set it to false. Did you miss to add dispatch(setIsFetchingTasks(false)) before return response.data;?
This could be the reason if your UI waits for the fetchingTasks to finish
After some researches, I found some questions on stackoverflow about what I am trying to achieve, however, I don't feel that these questions and their answers gives me the "answers" or the "directions" i am looking for..
Note: I am pretty new to react even if I already made 2 projects and implemented redux into one of them. However, I ain't new at all in C# or in Go, even less in C. Based on my experience, I am just used to some architectures and I would like to reproduce one of them.
Here is a pretyy good schema from a similar question of mine:
Situation:
So let say I have pages that contains Components. I want these pages/compoments to display some stuff. One of my functionnality is to discover a map and for that, when the client moves, he gets new parts from my API. However, I don't wanna ask the server to give me the new parts and the ones I discovered already.
My idea about it would be to use a service MapService.js. This one would just store the discovered pieces of the map discovered and ask the server automatically about the new ones, and of course, store the new ones (concat).
However, I have to be logged for this, so I would like an ApiService.js that would store my authentication data and automatically put them in each of my requests.
Based on what I said, we would have something as:
Page -> Component -> Service -> API
From this, the API response would be gotten by my service, handled, then returned to the component. Handled means (data added to the previous then all returned)
I saw on internet one question that was referring "MVCS" (Model View Controller Service) pattern and I think I am looking for something as but I am not sure about how to implement it in ReactJs.
Redux seems to be something that you put all around and everywhere in your solution. What I would like is to use it as a "repository" let say, to be able to manage it from a service and not from the component itself. However, a service should be a single instance shared across the app and I don't know if something such as dependency injection could be the solution in ReactJS
Feel free to ask any edit if you need more details :)
Thanks for your help !
Here is a minimal example of Redux middleware usage. Usually, redux devs are using libraries (that give you a middleware) to have access to more appropriate APIs.
Redux middleware are chained, so each middleware can call the next middleware. The first middleware of the chain is called every time dispatch function (you can have it from react-redux connect) is called. In a middleware, if there is no next middleware it is the reducers that will be called. The next middleware can be call asynchronously after receiving an action. (Redux docs will still be better than my explainations).
In my example there is a catService that provide function that call rest API. Your services can be anything (a Class instance or a singleton for example). Usually in React/Redux stack, devs don't use object oriented development.
If a component dispatch getCat(123), the catMiddleware will be called (synchronously). Then requestGetCat will be called with the id 123. When the promise returned by requestGetCat will be resolved a setCat action will be send through the reducers to update the redux state. Once the redux state is done, the component listening for cats items object will be update too (triggering a rerender).
That can look very complexe, but in fact, it is very scalable and convenient.
// catService.js
// return a promise that return a cat object
const requestGetCat = id =>
fetch(`www.catcat.com/api/cat/${id}`)
.then(response => response.json())
// catTypes.js
export const GET_CAT = 'GET_CAT'
export const SET_CAT = 'SET_CAT'
// catActions.js
export const getCat = id => ({
type: GET_CAT,
id
})
export const setCat = (cat, id) => ({
type: SET_CAT,
id,
cat
})
// catReducer.js
const initialState = {
items: {}
}
const catReducer = (state = initialState, action) => {
if (action.type === SET_CAT) {
return {
items: {
...state.items,
[action.id]: action.cat
}
}
}
}
// catMiddleware.js
const handleGetCat = (next, action) => {
requestGetCat(action.id)
.then(cat => next(setCat(cat, action.id)))
// after retrieving the cat send an action to the reducers (or next middleware if it exist)
}
const actionHandlers = {
[GET_CAT]: handleGetCat
}
// receive every actions passing by redux (if not blocked)
// store: { dispatch, getState }
// next: next middleware or reducers (that set redux state)
// action: a redux action (dispatched) with at least type property
const catMiddleware = store => next => action => {
const handler = actionHandlers[action.type]
if (handler) {
handler(next, action)
} else {
// passing the action to the next middleware (or reducer - when there is no next middleware)
next(action)
}
}
// you have to apply your middleware
// and your reducer (see redux doc)
This one would just store the discovered pieces of the map discovered and ask the server automatically about the new ones, and of course, store the new ones
This is something I've wanted to do in the past, but never implemented a solution for.
The issue is that you essentially want to "cross the streams"..
In Redux there are two separate streams, ie dispatch an action to update the store, and read data from the store. Each of these are executed separately from a component. Combined, they can be used in a cycle by calling an action to load data into the store which triggers an update of the component which then reads from the store.
Basically you can't have non-component code that reads from the store, and if the data is missing, fires an action to load the data, then returns the data.
Thinking about it now, I'm wondering if the way to do this without adding logic to your view component is to wrap it in a component (HOC) that provides the logic.
The HOC will check the state for the location specified in the props. If it doesn't find it, it will dispatch an action to fetch it and render a loading display. When the state is updated with the new location it will update and render the wrapped component.
You could optionally always render the wrapped component and have it cope with the missing location until it is updated with the location set..
untested brain-dump below
loader HOC:
import React, { useEffect } from "react";
import actions from "./actions";
function withLocationLoader(Component) {
const Wrapper = function ({ location, locations, loadLocation, ...props }) {
useEffect(() => {
if (!locations[location]) {
loadLocation(location);
}
}, [locations]);
if (locations[location]) {
return <Component locations={locations} {...props} />;
}
return <div>Loading...</div>;
}
const mapStateToProps = (state, ownProps) => {
return { locations: state.locations };
};
const mapActionsToProps = {
loadLocation: actions.loadLocation,
};
return connect(
mapStateToProps,
mapActionsToProps
)(Wrapper);
}
export { withLoader };
component:
function MyBareComponent({ locations }) {
return <div>{JSON.stringify(locations)}</div>;
}
const MyComponent = withLocationLoader(MyBareComponent);
export { MyComponent };
actions: (utilising redux-thunk middleware)
function setLocation(location, data) {
return { type: "SET_LOCATION", payload: { location, data } };
}
export function loadLocation(location) {
return dispatch =>
Promise.resolve({ geoData: "" }) // mock api request
.then(data => dispatch(setLocation(location, data)));
}
The title may not clear enough, please consider this example:
If I have a data table, which you can select multiple rows, and click action button like delete.
now in my actions.js:
(selectedRows is an array that contains the row indexes, getSelectedPostIds is a selector which will fetch and convert selectedRows to postIds)
import { getSelectedPostIds } from 'selectors'
export const deletePosts = () => (dispatch, getState) => {
// encapsulate the parameter `postIds` in action
const postIds = getSelectedPostIds(getState())
dispatch({ type: 'DELETE' })
deletePostsApi(postIds)
// .then(...)
// .catch(...)
}
is there any problem in this design? Or I should avoid using getState in an action and just pass postIds as a parameter to the action:
export const deletePosts = postIds => dispatch => {
dispatch({ type: 'DELETE' })
deletePostsApi(postIds)
// .then(...)
// .catch(...)
}
The only difference is that who should fetch the state (use the selector) from store, 1. action or 2. the component who will dispatch the action (via mapStateToProps).
I'm not sure about the approach 1, and the approach 2 will make my component contains a lot of props just because some actions need them (or maybe this is totally fine?).
thanks.
This might be a matter of taste. I usually like to access getState directly since, as you point out, avoids passing a lot of props. And by doing that the action is easier to integrate in different components (I just need to call it instead of additionally editing the mapStateToProps). Also, since in the end both ways are accessing the global store, the intended redux data flow is not compromised in any way.
You can use redux-thunk if you want to work with state in your action creators. :)
https://github.com/gaearon/redux-thunk
function yourActionCreator() {
// Redux-thunk will catch all action creators that return functions
return (dispatch, getState) => {
// u can use state here
const { counter } = getState();
if (counter % 2 === 0) {
return;
}
// Dispatch your action creator as you would normally do
dispatch(increment());
};
}