So what I'm trying to do is basically call an async function than ask mapStateIntoProps to pass it into props into the actual component. When I do I get a console.log() that shows pending my data is in there tho.
here is my first file that has the async func
export const getIdMovie = async (state,movieId)=>{
let data= await axios
.get(
`https://api.themoviedb.org/3/movie/${movieId}?
api_key=${APIKEY}&language=en-US`
)
let results=data.data
return results
}
this is where i try to call it on the second file
injectDataReducer(store, { key: "movie", reducer: MovieReducer });
const mapStateToProps = (state, ownProps) => ({
movie: getIdMovie(state,ownProps.movieId)
});
If getIdMovie is an action creator, you will have to use redux-thunk.Reducer updates the store asynchronously when you dispatch and action to avoid changing same data by multiple dispatch actions.
````Also, you will have to first set the state i.e. movies into reducer and then update the data from there into your component.```
Related
How can I get data from the store using React Redux Toolkit and get a cached version if I already requested it?
I need to request multiple users for example user1, user2, and user3. If I make a request for user1 after it has already been requested then I do not want to fetch user1 from the API again. Instead it should give me the info of the user1 from the store.
How can I do this in React with a Redux Toolkit slice?
Edit: This answer predates the release of RTK Query which has made this task much easier! RTK Query automatically handles caching and much more. Check out the docs for how to set it up.
Keep reading if you are interested in understanding more about some of the concepts at play.
Tools
Redux Toolkit can help with this but we need to combine various "tools" in the toolkit.
createEntityAdapter allows us to store and select entities like a user object in a structured way based on a unique ID.
createAsyncThunk will create the thunk action that fetches data from the API.
createSlice or createReducer creates our reducer.
React vs. Redux
We are going to create a useUser custom React hook to load a user by id.
We will need to use separate hooks in our hooks/components for reading the data (useSelector) and initiating a fetch (useDispatch). Storing the user state will always be the job of Redux. Beyond that, there is some leeway in terms of whether we handle certain logic in React or in Redux.
We could look at the selected value of user in the custom hook and only dispatch the requestUser action if user is undefined. Or we could dispatch requestUser all the time and have the requestUser thunk check to see if it needs to do the fetch using the condition setting of createAsyncThunk.
Basic Approach
Our naïve approach just checks if the user already exists in the state. We don't know if any other requests for this user are already pending.
Let's assume that you have some function which takes an id and fetches the user:
const fetchUser = async (userId) => {
const res = await axios.get(`https://jsonplaceholder.typicode.com/users/${userId}`);
return res.data;
};
We create a userAdapter helper:
const userAdapter = createEntityAdapter();
// needs to know the location of this slice in the state
export const userSelectors = userAdapter.getSelectors((state) => state.users);
export const { selectById: selectUserById } = userSelectors;
We create a requestUser thunk action creator that only executes the fetch if the user is not already loaded:
export const requestUser = createAsyncThunk("user/fetchById",
// call some API function
async (userId) => {
return await fetchUser(userId);
}, {
// return false to cancel
condition: (userId, { getState }) => {
const existing = selectUserById(getState(), userId);
return !existing;
}
}
);
We can use createSlice to create the reducer. The userAdapter helps us update the state.
const userSlice = createSlice({
name: "users",
initialState: userAdapter.getInitialState(),
reducers: {
// we don't need this, but you could add other actions here
},
extraReducers: (builder) => {
builder.addCase(requestUser.fulfilled, (state, action) => {
userAdapter.upsertOne(state, action.payload);
});
}
});
export const userReducer = userSlice.reducer;
But since our reducers property is empty, we could just as well use createReducer:
export const userReducer = createReducer(
userAdapter.getInitialState(),
(builder) => {
builder.addCase(requestUser.fulfilled, (state, action) => {
userAdapter.upsertOne(state, action.payload);
});
}
)
Our React hook returns the value from the selector, but also triggers a dispatch with a useEffect:
export const useUser = (userId: EntityId): User | undefined => {
// initiate the fetch inside a useEffect
const dispatch = useDispatch();
useEffect(
() => {
dispatch(requestUser(userId));
},
// runs once per hook or if userId changes
[dispatch, userId]
);
// get the value from the selector
return useSelector((state) => selectUserById(state, userId));
};
isLoading
The previous approach ignored the fetch if the user was already loaded, but what about if it is already loading? We could have multiple fetches for the same user occurring simultaneously.
Our state needs to store the fetch status of each user in order to fix this problem. In the docs example we can see that they store a keyed object of statuses alongside the user entities (you could also store the status as part of the entity).
We need to add an empty status dictionary as a property on our initialState:
const initialState = {
...userAdapter.getInitialState(),
status: {}
};
We need to update the status in response to all three requestUser actions. We can get the userId that the thunk was called with by looking at the meta.arg property of the action:
export const userReducer = createReducer(
initialState,
(builder) => {
builder.addCase(requestUser.pending, (state, action) => {
state.status[action.meta.arg] = 'pending';
});
builder.addCase(requestUser.fulfilled, (state, action) => {
state.status[action.meta.arg] = 'fulfilled';
userAdapter.upsertOne(state, action.payload);
});
builder.addCase(requestUser.rejected, (state, action) => {
state.status[action.meta.arg] = 'rejected';
});
}
);
We can select a status from the state by id:
export const selectUserStatusById = (state, userId) => state.users.status[userId];
Our thunk should look at the status when determining if it should fetch from the API. We do not want to load if it is already 'pending' or 'fulfilled'. We will load if it is 'rejected' or undefined:
export const requestUser = createAsyncThunk("user/fetchById",
// call some API function
async (userId) => {
return await fetchUser(userId);
}, {
// return false to cancel
condition: (userId, { getState }) => {
const status = selectUserStatusById(getState(), userId);
return status !== "fulfilled" && status !== "pending";
}
}
);
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.
In my redux action, I have one action will be called by another two actions, code is below:
export const addParticipantFromPopupRequest = (participant, project_id, currentStep) => async (dispatch) => {
const result = await addParticipant(participant)
dispatch({ type: PARTICIPANT_ADD, payload: result })
dispatch(updateProjectStep(project_id, currentStep))
}
export const handleFinalStep = (projectId, currentStep) => async (dispatch) => {
dispatch(updateProjectStep(projectId, currentStep))
}
const updateProjectStep = (projectId, currentStep) => async (dispatch, getState) => {
dispatch({ type: MODAL_STATUS_CHANGE, payload: { projectId, currentStep } })
dispatch({ type: PROJECT_PROCESS_LIST_UPDATE, payload: { project_id: projectId, currentStep } })
const { projectsProcessListsReducer } = getState()
localStorage.setItem("projectsProcessLists", JSON.stringify(projectsProcessListsReducer))
}
If I dont' use dispatch when call updateProjectStep, the addParticipantFromPopupRequest and handleFinalStep cannot run correct.
My question is can I call dispatch actions in this way and is it correct? Why I need the "dispatch" when I call updateProjectStep in another actions rather than call function name directly?
My question is can I call dispatch actions in this way and is it correct?
Yes. You should always call with the dispatch.
Why I need the "dispatch" when I call updateProjectStep in another actions rather than call function name directly?
If you call updateProjectStep directly without dispatch, it will become a normal js function call and your store won't be aware of it. Dispatch is the only way to trigger a state change in store.
In redux the store is single source of truth, the dispatch you are using is actually comes from store (store.dispatch).
If you call a function normally then it won't be aware by the store. That action won't pass through the middlewares (thunk/saga) that store is aware of and won't do the store update via reducers.
If store is not updated, your components won't receive any updates. Eventually your UI won't re-render.
You can find more about dispatch here.
In a component I have a button that onClick dispatches a deleteQuestion action that sends a fetch backend delete request, and when the response is received is supposed to call another action to update the Redux store.
However, since it's an onClick event, the deleteQuestion thunk function does not work like a traditional dispatch request made from ComponentWillMount and instead returns an anonymous function with a dispatch parameter that never is called. Therefore, I'm required to call the dispatch twice simultaneously in the onClick method like so:
handleDelete = () => {
const { questionId } = this.props.match.params
const { history } = this.props
deleteQuestion(questionId, history)(deleteQuestion); //calling method twice
}
While this approach is effective for trigging the delete request to the Rails backend, when I receive the response, the second dispatch function that I have embedded in the deleteQuestion action -- dispatch(removeQuestion(questionId)) -- won't trigger to update the Redux store. I've tried placing multiple debuggers in the store and checking console and terminal for errors, but nothing occurs.
I've read through the Redux docs and other resources online and from what I've been able to find they all say it should be possible to include a second dispatch call in a .then request. While it's possible to do this in get, post, and patch requests, I can't figure out why it won't work in a delete request.
The thunk call I make is:
export function deleteQuestion(questionId, routerHistory) {
return (dispatch) => {
fetch(`${API_URL}/questions/${questionId}`, {
method: 'DELETE',
}).then(res => {
dispatch(removeQuestion(questionId))
})
}
}
And the github is:
https://github.com/jwolfe890/react_project1/blob/master/stumped-app-client/src/actions/questions.js
I'd really appreciate any insight, as I've been trying to get passed this for two days now!
You are calling the action deleteQuestion directly instead of having your store dispatch the delete question action for you. You should instead call the deleteQuestion from your props that is already mapped to dispatch:
handleDelete = () => {
const { questionId } = this.props.match.params
const { history } = this.props
this.props.deleteQuestion(questionId, history);
}
If you pass in an object as mapDispatchToProps each element is dispatch call. In other words your mapDispatchToProps is equivalent to:
(dispatch) => ({
deleteQuestion: (...params) => dispatch(deleteQuestion(...params))
})
I have a chat-app that uses React, Redux and Firebase. I'm also using thunkmiddleware to do the async updates of the state with Firebase.
I successfully get everything I need, except that everything depends of a previously hard-coded variable.
The question is, how can I call inside my ActionCreators the getState() method in order to retrieve a piece of state value that I need in order to fill the rest of my states?
I currently have my auth: { uid = 'XXXZZZYYYY' }... I just need to call that like
getState().auth.uid
however that doesn't work at all.
I tried a lot of different questions, using mapDispatchToProps, etc. I can show my repo if needed.
Worth to mention that I tried following this other question without success.
Accessing Redux state in an action creator?
This is my relevant current code:
const store = createStore(
rootReducer,
defaultState,
applyMiddleware(thunkMiddleware));
And
function mapDispatchToProps(dispatch) {
watchFirebase(dispatch); // to dispatch async Firebase calls
return bindActionCreators(actionCreator, dispatch);
}
const App = connect(mapStateToProps, mapDispatchToProps)(AppWrapper);
Which I am exporting correctly as many other not pure functions work correctly.
For instance, this works correctly:
export function fillLoggedUser() {
return (dispatch, getState) => {
dispatch({
type: C.LOGGED_IN,
});
}
}
However as suggested below, this doesn't do a thing:
const logState = () => ( dispatch, getState ) => {
console.log(getState());
};
In general your thunked action creator should look something like the below (I have used a post id as an example parameter):
const getPost = ( postId ) => ( dispatch, getState ) => {
const state = getState();
const authToken = state.reducerName.authToken;
Api.getPost(postId, authToken)
.then(result => {
// where postRetrieved returns an action
dispatch(postRetrieved(result));
});
};
If this is similar to what you have then I would log your state out and see what is going on with a simple thunk.
const logState = () => ( dispatch, getState ) => {
console.log(getState());
};