I refactoring the store in my project with redux toolkit and we use also redux sagas;
So I have a slice with an action:
createTask: (state: myTypeState, action:PayloadAction<myTypeState>) => {
state.createTaskStatus = status.fetching
},
In my sagas I connect the two part like that:
takeLatest(createTask().type, mySagaFunction),
In my component I use it like that with 3 parameters, needed for my saga:
dispatch(createTask({
name,
pictureFile: picture,
jobstation,
}))
But in my action I didn't use the second parameters and so I have an eslint warning:
`Unused parameter action``
How can I fix that warning ?
ps: I have also try to connect toolkit and sagas like that:
export const createTaskAction = createAction(types.CREATE_TASK)
and
takeLatest(CREATE_TASK, createTask),
With that, i need to dispatch this createTaskAction and the goal is to remove as much code as possible ^^
what is the best way to do it?
This will work without Unused parameter action:
createTask: (state: myTypeState) => {
state.createTaskStatus = status.fetching
},
Related
I'm implementing a simple favorites list. Currently there's no backend part so it will be persisted in localStorage. In the future it may become an API call.
Is it okay to call localStorage.setItem
and localStorage.getItem from within a rtk slice?
For example:
createSlice({
name: "slice",
initialState,
extraReducers: extraReducers,
reducers: {
setLocalStorageThing: (
state,
action: PayloadAction<{ payload: string }>
) => {
let localStoragething= JSON.parse(
localStorage.getItem("key")
);
if (localStorageThing !== payload) {
localStorage.setItem(
"key",
JSON.stringify(payload)
);
}
},
}
Alternatively, is this possible as a thunk? Ultimately I'd like to be able to use the useSelector hook to access this information, so when the swap happens I only have to change the action/reducer in the slice. This seems like a side effect, but I'm not sure the harm in it. It has already been done else where in the code without issue (so far).
It's not recommended to deal with localStore inside reducers because they must be pure https://redux.js.org/understanding/thinking-in-redux/three-principles. You can use a thunk to deal with it
Writing logic for local storage inside reducers will not break the application. But it breaks the rules of writing reducers, i.e reducers should not cause "side effects". See the rules here. In short, it means try to make reducers be all concerned about redux. One way to solve your problem in sync with redux recommendations, is to use a middleware before a particular action type has been run.
When creating a React app, if I use the hook useSelector, I need to adhere to the hooks invoking rules (Only call it from the top level of a functional component). If I use the mapStateToProps, I get the state in the props and I can use it anywhere without any issues... Same issue for useDispatch
What are the benefits of using the hook besides saving lines of code compared to mapStateToProps?
Redux store state can be read and changed from anywhere in the component, including callbacks. Whenever the store state is changed the component rerenders. When the component rerenders, useSelector runs again, and gives you the updated data, later to be used wherever you want. Here is an example of that and a usage of useDispatch inside a callback (after an assignment in the root level):
function Modal({ children }) {
const isOpen = useSelector(state => state.isOpen);
const dispatch = useDispatch();
function handleModalToggeled() {
// using updated data from store state in a callback
if(isOpen) {
// writing to state, leading to a rerender
dispatch({type: "CLOSE_MODAL"});
return;
}
// writing to state, leading to a rerender
dispatch({type: "OPEN_MODAL"});
}
// using updated data from store state in render
return (isOpen ? (
<div>
{children}
<button onClick={handleModalToggeled}>close modal</button>
</div>
) : (
<button onClick={handleModalToggeled}>open modal</button>
);
);
}
There is nothing you can do with mapStateToProps/mapDispatchToProps that you can't do with the useSelector and useDispatch hooks as well.
With that said, there are a couple of differences between the two methods that are worth considering:
Decoupling: with mapStateToProps, container logic (the way store data is injected into the component) is separate from the view logic (component rendering).
useSelector represents a new and different way of thinking about connected components, arguing that the decoupling is more important between components and that components are self contained. Which is better? Verdict: no clear winner. source
DX (Developer experience): using the connect function usually means there should be another additional container component for each connected component, where using the useSelector and useDispatch hooks is quite straightforward. Verdict: hooks have better DX.
"Stale props" and "Zombie child": there are some weird edge cases with useSelector, if it depends on props, where useSelector can run before the newest updated props come in. These are mostly rare and avoidable edge cases, but they had been already worked out in the older connect version. verdict: connect is slightly more stable than hooks. source
Performance optimizations: both support performance optimizations in different ways: connect has some advanced techniques, using merge props and other options hidden in the connect function. useSelector accepts a second argument - an equality function to determine if the state has changed. verdict: both are great for performance in advanced situations.
Types: using typescript with connect is a nightmare. I remember myself feverishly writing three props interfaces for each connected component (OwnProps, StateProps, DispatchProps). Redux hooks support types in a rather straightforward way. verdict: types are significantly easier to work with using hooks.
The future of React: Hooks are the future of react. This may seam like an odd argument, but change to the ecosystem is right around the corner with "Concurrent mode" and "Server components". While class components will still be supported in future React versions, new features may rely solely on hooks. This change will of course also affect third party libraries in the eco system, such as React-Redux. verdict: hooks are more future proof.
TL;DR - Final verdict: each method has its merits. connect is more mature, has less potential for weird bugs and edge cases, and has better separation of concerns. Hooks are easier to read and write, as they are collocated near the place where they are used (all in one self contained component). Also, they are easier to use with TypeScript. Finally, they will easily be upgradable for future react versions.
I think you misunderstand what "top level" is. It merely means that, inside a functional component, useSelector() cannot be placed inside loops, conditions and nested functions. It doesn't have anything to do with root component or components structure
// bad
const MyComponent = () => {
if (condition) {
// can't do this
const data = useSelector(mySelector);
console.log(data);
}
return null;
}
---
// good
const MyComponent = () => {
const data = useSelector(mySelector);
if (condition) {
console.log(data); // using data in condition
}
return null;
}
If anything, mapStateToPtops is located at even higher level than a hook call
the rules of hooks make it very hard to use that specific hook. You still need to somehow access a changing value from the state inside callbacks
To be fair you almost never have to access changing value inside a callback. I can't remember last time I needed that. Usually if your callback needs the latest state, you are better off just dispatching an action and then handler for that action (redux-thunk, redux-saga, redux-observable etc) will itself access the latest state
This is just specifics of hooks in general (not just useSelector) and there are tons of ways to go around it if you really want to, for example
const MyComponent = () => {
const data = useSelector(mySelector);
const latestData = useRef()
latestData.current = data
return (
<button
onClick={() => {
setTimeout(() => {
console.log(latestData.current) // always refers to latest data
}, 5000)
}}
/>
)
}
What are the benefits of using the hook besides saving lines of code compared to mapStateToProps?
You save time by not writing connect function any time you need to access store, and removing it when you no longer need to access store. No endless wrappers in react devtools
You have clear distinction and no conflicts between props coming from connect, props coming from parent and props injected by wrappers from 3rd party libraries
Sometimes you (or fellow developers you work with) would choose unclear names for props in mapStateToProps and you will have to scroll all the way to mapStateToProps in the file to find out which selector is used for this specific prop. This is not the case with hooks where selectors and variables with data they return are coupled on the same line
By using hooks you get general advantages of hooks, the biggest of which is being able couple together and reuse related stateful logic in multiple components
With mapStateToProps you usually have to deal with mapDispatchToProps which is even more cumbersome and easier to get lost in, especially reading someone else's code (object form? function form? bindActionCreators?). Prop coming from mapDispatchToProps can have same name as it's action creator but different signature because it was overridden in mapDispatchToprops. If you use one action creator in a number of components and then rename that action creator, these components will keep using old name coming from props. Object form easily breaks if you have a dependency cycle and also you have to deal with shadowing variable names
.
import { getUsers } from 'actions/user'
class MyComponent extends Component {
render() {
// shadowed variable getUsers, now you either rename it
// or call it like this.props.getUsers
// or change import to asterisk, and neither option is good
const { getUsers } = this.props
// ...
}
}
const mapDispatchToProps = {
getUsers,
}
export default connect(null, mapDispatchToProps)(MyComponent)
See EDIT 2 at the end for the final answer
Since no one knows how to answer, it seems like the best answer is that you should NOT be using useselector when you need information in other places other than the root level of your component. Since you don't know if the component will change in the future, just don't use useselector at all.
If someone has a better answer than this, I'll change the accepted answer.
Edit: Some answers were added, but they just emphasize why you shouldn't be using useselector at all, until the day when the rules of hooks will change, and you'll be able to use it in a callback as well. That being said, if you don't want to use it in a callback, it could be a good solution for you.
EDIT 2: An answer with examples of all that I wanted was added and showed how useSelector and useDispatch are easier to use.
The redux state returned from the useSelector hook can be passed around anywhere else just like its done for mapStateToProps. Example: It can be passed to another function too. Only constraint being that the hook rules has to be followed during its declaration:
It has to be declared only within a functional component.
During declaration, it can not be inside any conditional block . Sample code below
function test(displayText) {
return (<div>{displayText}</div>);
}
export function App(props) {
const displayReady = useSelector(state => {
return state.readyFlag;
});
const displayText = useSelector(state => {
return state.displayText;
});
if(displayReady) {
return
(<div>
Outer
{test(displayText)}
</div>);
}
else {
return null;
}
}
EDIT: Since OP has asked a specific question - which is about using it within a callback, I would like to add a specific code.In summary, I do not see anything that stops us from using useSelector hook output in a callback. Please see the sample code below, its a snippet from my own code that demonstrates this particular use case.
export default function CustomPaginationActionsTable(props) {
//Read state with useSelector.
const searchCriteria = useSelector(state => {
return state && state.selectedFacets;
});
//use the read state in a callback invoked from useEffect hook.
useEffect( ()=>{
const postParams = constructParticipantListQueryParams(searchCriteria);
const options = {
headers: {
'Content-Type': 'application/json'
},
validateStatus: () => true
};
var request = axios.post(PORTAL_SEARCH_LIST_ALL_PARTICIPANTS_URI, postParams, options)
.then(function(response)
{
if(response.status === HTTP_STATUS_CODE_SUCCESS) {
console.log('Accessing useSelector hook output in axios callback. Printing it '+JSON.stringify(searchCriteria));
}
})
.catch(function(error) {
});
}, []);
}
For callback functions you can use the value returned from useSelector the same way you would use the value from useState.
const ExampleComponent = () => {
// use hook to get data from redux state.
const stateData = useSelector(state => state.data);
// use hook to get dispatch for redux store.
// this allows actions to be dispatched.
const dispatch = useDispatch();
// Create a non-memoized callback function using stateData.
// This function is recreated every rerender, a change in
// state.data in the redux store will cause a rerender.
const callbackWithoutMemo = (event) => {
// use state values.
if (stateData.condition) {
doSomething();
}
else {
doSomethingElse();
}
// dispatch some action to the store
// can pass data if needed.
dispatch(someActionCreator());
};
// Create a memoized callback function using stateData.
// This function is recreated whenever a value in the
// dependency array changes (reference comparison).
const callbackWithMemo = useCallback((event) => {
// use state values.
if (stateData.condition) {
doSomething();
}
else {
doSomethingElse();
}
// dispatch some action to the store
// can pass data if needed.
dispatch(someActionCreator());
}, [stateData, doSomething, doSomethingElse]);
// Use the callbacks.
return (
<>
<div onClick={callbackWithoutMemo}>
Click me
</div>
<div onClick={callbackWithMemo}>
Click me
</div>
</>
)
};
Rules of hooks says you must use it at the root of your component, meaning you CANT use it anywhere.
As Max stated in his answer just means that the hook statement itself must not be dynamic / conditional. This is because the order of the base hooks (react's internal hooks: useState, etc) is used by the backing framework to populate the stored data each render.
The values from hooks can be used where ever you like.
While I doubt this will be close to answering your complete question, callbacks keep coming up and no examples had been posted.
not the answer but this hook can be very helpful if you want to get decoupled nature of mapDispatchToProps while keeping simplicity and dev experience of hooks:
https://gist.github.com/ErAz7/1bffea05743440d6d7559afc9ed12ddc
the reason I don't mention one for mapStatesToProps is that useSelector itself is more store-logic-decoupling than mapStatesToProps so don't see any advantage for mapStatesToProps. Of course I dont mean using useSelector directly but instead create a wrapper on it in your store files (e.g. in reducer file) and import from there, like this:
// e.g. userReducer.js
export const useUserProfile = () => useSelector(state => state.user.profile)
I am new to React, Redux and JS overall. I want to know how can I chain actions in a component? On a listing screen, my application retrieves user's Geo Position then it fetching api url with current long and lat.
I made it with time out. But I see it's a risky way.
import {
aFetch,
aGetPosition,
} from '../../actions';
import { API_URL } from '../../config/ApiEndpoints';
class App extends Component {
componentDidMount() {
this.props.aGetPosition();
setTimeout(() => {
const { latitude, longitude } = this.props.position.data.coords;
const url = `${API_URL}=${latitude},${longitude}`;
this.props.aFetch(url);
}, 1000);
}
render(){...}
}
const mapStateToProps = (state) => {
return {
position: state.position,
items: state.items,
};
};
export default connect(mapStateToProps, { aFetch, aGetPosition })(App);
Is possible to make it using .then() or something equal?
I believe you need the method componentWillReceiveProps(). The docs provide a good explanation about it and other methods in the lifecycle of a component.
Firstly, you'll want to dispatch your redux actions. This is possible by using a mapDispatchToProps function, which will be the 2nd parameter in your connect function (instead of a plain object with your actions, which is what you have now). Docs on implementing redux within your React containers, including dispatching actions from your container: http://redux.js.org/docs/basics/UsageWithReact.html#implementing-container-components
To handle async actions and chaining actions, you'll likely want to use a middleware to help you, such as redux-thunk. Doc link: http://redux.js.org/docs/advanced/AsyncActions.html#async-action-creators (I recommend reading this whole page, but the link will go directly to the section for redux-thunk).
I am iteratively rebuilding a legacy system to use React / Redux. It's been working great for the most part! The big problem facing me right now is that the old system had a lot of nested iframes that would use top.functionName() to communicate with the rest of the application. Since I can't rebuild everything at once, I need to write some sort of interface to communicate with my Redux store via top.functionName().
I know I can use $r.store.dispatch to send an action straight to the reducers, but I'd really like to use my action creators directly if possible. Is there a way to accomplish this?
Create an object with the actions wrapped with dispatch, and set the object as a property on window:
Import all your actions as one object, or combine them all to an object using spread or Object#assign.
//import * as actionCreators1 from actionCreators1
//import * as actionCreators2 from actionCreators2
//import * as actionCreators3 from actionCreators3
const actionCreators = { ...actionCreators1, ...actionCreators2, ...actionCreators3, etc... };
The actions' object should be something like this
const actionCreators = {
actionA: (payload) => ({ type: 'actionA', payload }),
actionB: (payload) => ({ type: 'actionB', payload }),
// etc...
};
Wrap the actions with dispatch using bindActionCreators, and assign them to a property on window:
const demoStore = createStore(reducer);
window.reduxActions = bindActionCreators(actionCreators, demoStore.dispatch);
Call your actions from the iframes using:
top.reduxActions.actionA(15);
I've developed a smallish standalone web app with React and Redux which is hosted on its own web server. We now want to reuse/integrate most parts of this app into another React/Redux web app.
In theory this should work quite nicely because all my React components, reducers and most action creators are pure. But I have a few action creators which return thunks that depend on the app state. They may dispatch async or sync actions, but that's not the issue here.
Let's say my root reducer looks like this:
const myAppReducer = combineReducers({
foo: fooReducer,
bar: barReducer,
baz: bazReducer
});
and my most complex action creators depend on many state slices (luckily there are only a few of those):
const someAction = function () {
return (dispatch, getState) => {
const state = getState();
if (state.foo.someProp && !state.bar.anotherProp) {
dispatch(fetchSomething(state.baz.currentId);
} else {
dispatch(doSomethingSynchronous());
}
};
}
Now the problem is that my action creators expect everything to be inside the root of the state object. But if we want to integrate this app into another redux app we'll have to mount my appReducer with its own key:
// The otherAppReducer that wants to integrate my appReducer
const otherAppReducer = combineReducers({
....
myApp: myAppReducer
});
This obviously breaks my action creators that return thunks and need to read app state, because now everything is contained in the "myApp" state slice.
I did a lot of research and thinking how to properly solve this the last few days, but it seems I'm the first one trying to integrate a Redux based app into another Redux based app.
A few hacks/ideas that came to mind so far:
Create my own thunk type so I can do instanceof checks in a custom thunk middleware and make it pass my thunks a custom getState function which will then return the correct state slice.
Mount my root reducer with it's own key and make my thunks depend on that key.
So far I think the best approach would be to create my own custom middleware, but I'm not really happy with the fact that other apps will now depend on my middleware and custom thunk type. I think there must be a more generic approach.
Any ideas/suggestions? How would you solve this kind of problem?
Have you considered not depending on store.getState()? I would decouple the actions from the application state altogether and take in the data you need from where the actions are called.
So for example:
const someAction = function (someProp, anotherProp, currentId) {
return dispatch => {
if (someProp && !anotherProp) {
dispatch(fetchSomething(currentId);
} else {
dispatch(doSomethingSynchronous());
}
};
}
This makes the actions totally reusable, with the downside of you having to now have that information elsewhere. Where else? If convenient, inside your component using this.context.store, or via props with connect, or maybe better, by having wrapper actions for your specific applications, so:
const someApplicationAction = () => {
return (dispatch, getState) => {
const { foo, bar, baz } = getState();
dispatch(someGenericAction(foo.someProp, bar.anotherProp, baz.currentID));
};
}