I'm building an app in React Native, and using Redux with redux-persist to act as on device database.
The crux of the issue is, how do I return the result of a redux action, to then dispatch another action with this data? Read on for more specifics.
The user can create custom habit types. When doing so, I dispatch an action to create a habit type in the store (e.g. "running"). This action generates a new unique UUID for the habit type. I then want to add this newly created habit type to a routine (e.g. "morning routine"), and so I need to receive back the UUID of the habit type and call another dispatch to add it to the routine.
I'm using immer to make manipulating the state in my reducers simpler, and have this code (simplified example):
import produce from "immer";
const userReducer = (state = initialState, action) => {
switch (action.type) {
case ADD_CUSTOM_HABIT_TYPE: {
return produce(state, draftState => {
const newHabitType = {
id: generateUuid(),
name,
};
draftState.customHabitTypes.push(newHabitType);
return draftState;
});
}
}
};
I'm then dispatching it in my component, like so (simplified):
dispatch({
type: ADD_CUSTOM_HABIT_TYPE,
name: "running",
});
How can I then say, after creating this new habit type, to dispatch another action and add it to my routine?
I've looked at redux-thunk and redux-saga, and spent hours reading about these and trying to get redux-thunk to work, but to no avail. I'm sure this must be simple, but I'm coming up blank, and so maybe others are too, hence this post.
A very simple solution would be to generate the unique id before dispatching the action.
Example
const newHabitType = {
id: generateUuid(),
name,
};
dispatch({
type: ADD_CUSTOM_HABIT_TYPE,
habit: newHabitType,
});
dispatch({
type: ADD_CUSTOM_HABIT_TO_ROUTINE,
habit: newHabitType.id,
});
Pros
You no longer need to chain actions per se, you just need to dispatch them in order.
This preserves one of the most important Redux guidelines: your reducer should not have any side effects (in your case, generating a random id). reference
Cons
If you create the new habits in multiple places, you will have to generate the unique ids in every place where you dispatch the action. This might lead to repeated code. The solution to this would be to encapsulate the whole logic for creating the habits to a single component and then reuse this component everywhere.
Actions do not return data per se, the are simply objects which mutate the store based on the rules defined in the reducer. Two possible solutions:
Option A, create a composite action.
const compositeAction = args => {
return dispatch => {
return someAsyncCall(args).then(response => {
dispatch(addCustomHabitat(response))
dispatch(followUpAction())
}
}
}
const addCustomHabitat = response => {
return {
type: "ADD_CUSTOM_HABIT_TYPE",
data: response
}
}
const followUpAction = () => {
...another action...
}
Option B, connect the results of the first action to the dispatching component through react-redux and pass them to the second action.
import {connect} from 'react-redux';
const MyReactComponent = props => {
dispatch(addCustomHabitatTypeAction());
if(props.customHabitatType !== undefined)
dispatch(followUpAction(props.customHabitatType());
return (
...JSX here...
);
}
const mapStateToProps = state => {
return {
customHabitatType: state.userReducer.customHabitatType
}
}
connect(mapStateToProps)(MyReactComponent);
I hope this helps! Please excuse my abbreviated code and let me know if you have any questions.
Related
I'm trying to create an object and add it to a reducer, but have the action/reducer take care of generating the id.
Per this answer, it seems the accepted pattern is to generate the id in the action creator:
const todosSlice = createSlice({
name: "todos",
initialState: [],
reducers: {
addTodo: {
reducer(state, action) {
state.push(action.payload);
},
prepare(text) {
const id = uuid();
return { payload: {text, id} };
}
}
}
})
However, suppose I want to then use / refer to the id after creating the todo, something like
dispatch(addTodo('Say hello world')) // creates a todo with a uuid
...
id = <some way to get the id>
doSomethingElseWithTodoGivenId()
Does Redux-Toolkit provide any assistance with achieving this? I looked at createAsyncThunk, but that appears to be more focussed around async data fetching status.
I know I can do this with redux-thunk (by awaiting the dispatch and having the thunk action generate the id):
const id = await dispatch(createTodoWithGeneratedId('Say hello world'))
or by having the caller generate the id. But I'm wondering if there's a better way.
Unfourtonately, dispatch is not working that way. Plain Redux dispatch call retuns a dispatched action, but redux-toolkit using thunk middleware by default that changes a dispatch returning value to promise that fullfiled with dispatched action. You can't get a result of dispatching result from dispatch call itself, it is impossible and conflicts with it's nature.
However, you can create a thunk that dispatches different actions based on promise result. Check official documentation about creating thunk with side effects. For more advanced usage check this answer in SO.
If you are using redux-toolkit, you can use createAsyncThunk, it is implements the same logic but without much more boilerplate code.
There is no accepted pattern in this case. Sometimes you have to figure out things based on your needs. That is why leetcode algorithms are such a big deal in hiring process.
If you follow your above implementation
import { nanoid } from '#reduxjs/toolkit';
prepare(text) {
const id = nanoid();
return { payload: {text, id} };
}
the only way to get the "id" is you have to get the state with the useSelector and then loop through where text===currentToDo. This is too much work for a simple task.
Instead, why not pass id with the dispatching? You arrange your payload where accepts an object. (Because you cannot pass multiple args)
const id=nanoid()
dispatch(addTodo({todo:'Say hello world',id:id}))
// now use that id todo something
in this scenario, you do not even need the prepare phase. (you did not before neither). just push the payload object to the array
I have made some research about possible ways to do it, but I can't find one that uses the same architecture like the one in the app I'm working on. For instance, React docs say that we should have a method which makes the HTTP request and then calls actions in different points (when request starts, when response is received, etc). But we have another approach. We use an action which makes the HTTP call and then dispatches the result. To be more precise, my use case is this:
// action to get resource A
getResourceA () {
return dispatch => {
const result = await axios.get('someLink');
dispatch({
type: GET_RES_A,
payload: result
});
};
}
// another action which needs data from resource A
getSomethingElseByIdFromA (aId) {
return async dispatch => {
const result = await axiosClient.get(`someLink/${aId}`);
dispatch({
type: GET_SOMETHING_BY_ID_FROM_A,
payload: result
});
};
}
As stated, the second action needs data from the first one.
Now, I know of two ways of doing this:
return the result from the first action
getResourceA () {
return async dispatch => {
const result = await axios.get('someLink');
dispatch({
type: GET_RES_A,
payload: result
});
return result;
};
}
// and then, when using it, inside a container
async foo () {
const {
// these two props are mapped to the getResourceA and
// getSomethingElseByIdFromA actions
dispatchGetResourceA,
dispatchGetSomethingElseByIdFromA
} = this.props;
const aRes = await dispatchGetResourceA();
// now aRes contains the resource from the server, but it has not
// passed through the redux store yet. It's raw data
dispatchGetSomethingElseByIdFromA(aRes.id);
}
However, the project I'm working on right now wants the data to go through the store first - in case it must be modified - and only after that, it can be used. This brought me to the 2nd way of doing things:
make an "aggregate" service and use the getState method to access the state after the action is completed.
aggregateAction () {
return await (dispatch, getState) => {
await dispatch(getResourceA());
const { aRes } = getState();
dispatch(getSomethingElseByIdFromA(aRes.id));
};
}
And afterward simply call this action in the container.
I am wondering if the second way is all right. I feel it's not nice to have things in the redux store just for the sake of accessing them throughout actions. If that's the case, what would be a better approach for this problem?
I think having/using an Epic from redux-observable would be the best fit for your use case. It would let the actions go throughout your reducers first (unlike the mentioned above approach) before handling them in the SAME logic. Also using a stream of actions will let you manipulate the data throughout its flow and you will not have to store things unnecessary. Reactive programming and the observable pattern itself has some great advantages when it comes to async operations, a better option then redux-thunk, sagas etc imo.
I would take a look at using custom midleware (https://redux.js.org/advanced/middleware). Using middleware can make this kind of thing easier to achieve.
Something like :
import {GET_RESOURCE_A, GET_RESOURCE_B, GET_RESOURCE_A_SUCCESS, GET_RESOURCE_A_ERROR } from '../actions/actionTypes'
const actionTypes = [GET_RESOURCE_A, GET_RESOURCE_B, GET_RESOURCE_A_SUCCESS, GET_RESOURCE_A_ERROR ]
export default ({dispatch, getState}) => {
return next => action => {
if (!action.type || !actionTypes.includes(action.type)) {
return next(action)
}
if(action.type === GET_RESOURCE_A){
try{
// here you can getState() to look at current state object
// dispatch multiple actions like GET_RESOURCE_B and/ or
// GET_RESOURCE_A_SUCCESS
// make other api calls etc....
// you don't have to keep stuff in global state you don't
//want to you could have a varaiable here to do it
}
catch (e){
} dispatch({type:GET_RESOURCE_A_ERROR , payload: 'error'})
}
}
}
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)));
}
I am building a Redux application (my first) and am a little unclear about how much coupling is appropriate between actions.
My application has several forms whose values are serialized in the url.
For example, there is an input field for a particular search, and upon key-up a url parameter is updated. There are several other input fields that follow this pattern.
In my top-level index.js I have several blocks of code that look like this:
// Within the declaration of a high-level component
onForm1Change={(key, value) => {
// Listened to by "formValues" state cross-section reducer
store.dispatch({
type: actions.FORM1_CHANGE,
key: key,
value: value
});
// Listened to by "url" state cross-section reducer, leads to a url param update.
// Has it's own logic that is based upon the formValues state.
// Must run after FORM1_CHANGE finishes
store.dispatch({
type: actions.UPDATE_URL,
formValues: store.getState().formValues
});
}
}
Something about actions like UPDATE_URL doesn't feel right. This action doesn't stand on its own...it relies on other actions to be dispatched first.
Is this sort of coupling between actions a code smell? Are there any common techniques to de-couple/refactor these actions?
I think that's totally OK way of chaining synchronous actions. You can also use middleware like redux-thunk for this purpose to make it simpler to read (as you will store your actions dispatcher function as an action creater). Here is some article on this topic.
This is how i did it,
Defined a redux store middleware that will detect if any dispatched action has a queryString property, and update url with it.
import createHistory from "history/createBrowserHistory";
function queryStringMiddleware(history) {
return store => next => action => {
const { payload } = action;
if (payload.queryString) {
history.push({
search: queryString
});
}
next(action);
};
}
const history = createHistory();
const middlewares = [queryStringMiddleware(history)];
const store = configureStore({}, middlewares);
Then in your action:
const onForm1Change = (key, value) => {
store.dispatch({
type: actions.FORM1_CHANGE,
key: key,
value: value,
queryString: "?the=query"
});
};
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());
};
}