I've tried
initiate - but this result was retrieved from previous result.
mutate - but I think this is irregular.
Is there any way to use await for a normal get request?
relevant questions:
Approaches for using RTK-Query hooks inside functions?
https://www.reddit.com/r/reduxjs/comments/pvvpwy/is_there_a_way_to_await_for_an_rtk_query_response/
Specifically, I want to do the following:
useEffect(() => {
someRTKQuerysGetMethod()
.then(data => setValuesToForm(data))
}, [])
However, the comment I received from phry may have solved the problem.
I updated to v1.7
use "useLazyQuery" and unwrap()
const [getPokemon] = useLazyGetPokemonQuery()
useEffect(() => {
getPokemon({...})
.unwrap()
.then(data => setValuesToForm(data))
}, [])
Thank you very much...!!
You can use the useLazyQuery hook with the unwrap method.
// Get the trigger
const [getPokemon] = useLazyGetPokemonQuery();
// Then you can call with await
await getPokemon().unwrap();
// Or with standard promise
getPokemon()
.unwrap()
.then((fulfilled) => console.log(fulfilled))
.catch((rejected) => console.error(rejected));
Related
return this.usersTableService.fetchRequestedPageUsersIds(request).pipe(
switchMap((idsToFetch) => {
requestedIds = idsToFetch;
return [this.usersTableService.getNewIdsToFetch(requestedIds, entities), of(idsToFetch)];
}),
//.......?(([newIds, idsToFetch]) => {
return this._fetchNewUsersFromAPI(requestedIds, request, newIds, entities);
}),
catchError((err) => of(loadPageFail(err)))
);
what operator should I use in order to get the value of the return tuple before ?
You can use forkJoin for this
return this.usersTableService.fetchRequestedPageUsersIds(request).pipe(
switchMap((idsToFetch) => {
return forkJoin([this.usersTableService.getNewIdsToFetch(requestedIds, entities), of(idsToFetch)]);
}),
mergeMap(([newIds, idsToFetch]) => {
return this._fetchNewUsersFromAPI(requestedIds, request, newIds, entities);
}),
catchError((err) => of(loadPageFail(err)))
)
You would normally use the map operator(https://stackblitz.com/edit/so-tuple-map?file=index.ts):
const obs$ = of(1).pipe(map(y => ['abc', 'def']), map(([str1, str2]) => str1 + str2))
But if you try that you will encounter other issues with your code ie:
its not good practice to store a local variable inside a switchMap then return it using of
_fetchNewUsersFromAPI needs to be inside a switchMap
Ultimately you'll still be faced with the fundamental problem of how to pass parameters down the observable chain, which I suspect is how you've ended up in this situation to begin with.
There is currently a bountied question asking about the same problem here: How to pass results between chained observables
IMO the best solution from that question is to use nested pipes ie:
const newUsers$ = requestsSubject.pipe(
switchMap(request =>
this.usersTableService.fetchRequestedPageUsersIds(request).pipe(
switchMap(idsToFetch =>
this.usersTableService.getNewIdsToFetch(idsToFetch).pipe(
switchMap(newIds =>
this._fetchNewUsersFromAPI(idsToFetch, request, newIds, entities)
)
)
)
)
)
);
An alternative way using await and toPromise:
function getUsers(request){
const idsToFetch = await this.usersTableService.fetchRequestedPageUsersIds(request).toPromise();
const newIds = await this.usersTableService.getNewIdsToFetch(idsToFetch, entities).toPromise();
const newUsers = await this._fetchNewUsersFromAPI(idsToFetch, request, newIds, entities).toPromise();
return newUsers;
}
I want to create a function that will make AJAX requests to backend. And if this function is called many times at the same time, then it should not make many identical requests to the server. It must make only 1 request.
For example:
doAJAX('http://example-1.com/').subscribe(res => console.log); // must send a request
doAJAX('http://example-1.com/').subscribe(res => console.log); // must NOT send a request
doAJAX('http://example-2.com/').subscribe(res => console.log); // must send a request, bacause of different URL
window.setTimeout(() => {
doAJAX('http://example-2.com/').subscribe(res => console.log); // must send a request because too much time has passed since the last request
}, 3000)
All function calls should return a result, as if the request was actually made.
I think for this purpose I can use RxJS library.
I have done this:
const request$ = new Subject < string > ();
const response$ = request.pipe(
groupBy((url: string) => url),
flatMap(group => group.pipe(auditTime(500))), // make a request no more than once every 500 msec
map((url: string) => [
url,
from(fetch(url))
]),
share()
);
const doAJAX = (url: string): Observable <any> {
return new Observable(observe => {
response$
.pipe(
filter(result => result[0] === url),
first(),
flatMap(result => result[1])
)
.subscribe(
(response: any) => {
observe.next(response);
observe.complete();
},
err => {
observe.error(err);
}
);
request$.next(url);
});
}
I create request$ subject and response$ observable. doAjax function subscribes for response$ and send URL string to request$ subject. Also there are groupBy and auditTime operators in request$ stream. And filter operator in doAJAX function.
This code works but I think it is very difficult. Is there a way to make this task easier? Maybe RxJS scheduler or not use RxJS library at all
As the whole point of this is to memoize Http results and delay repeated calls, you might consider your own memoization. Example:
const memoise = (func) => {
let cache: { [key:string]: Observable<any> } = {};
return (...args): Observable<any> => {
const cacheKey = JSON.stringify(args)
cache[cacheKey] = cache[cacheKey] || func(...args).pipe(share());
return cache[cacheKey].pipe(
tap(() => timer(1000).subscribe(() => delete cache[cacheKey]))
);
}
}
Here is a Stackblitz DEMO
I have the following searchService.search method that returns a forkJoin of two api calls.
I want the calls to execute simultaneously which they are but I also want each response back as a single object that can be passed into my SearchSuccess action and processed immediately without waiting for all calls to complete. Currently they are returning as an array of responses and only upon completion of both API calls - as this is what forkJoin is used for.
My issue is that I'm struggling to find another operator that does what I want.
Or perhaps the code pattern requires some redesign?
action:
#Effect()
trySearch: Observable<Action> = this.actions$.pipe(
ofType(SearchActionTypes.TrySearch),
switchMap((action: TrySearch) =>
this.searchService.search(action.payload)
.pipe(
map((data) => new SearchSuccess(data)),
catchError(error => of(new SearchFail(error))),
),
),
);
SearchService (snippet):
search(searchForm: SearchForm): Observable<any> {
const returnArray = [];
if (searchForm.searchClients) {
const searchClientParams = new Search();
searchClientParams.searchPhrase = searchForm.searchPhrase;
searchClientParams.type = SearchType.Client;
const searchClients = this.objectSearch(searchClientParams);
returnArray.push(searchClients);
}
if (searchForm.searchContacts) {
const searchContactParams = new Search();
searchContactParams.searchPhrase = searchForm.searchPhrase;
searchContactParams.type = SearchType.Contact;
const searchContacts = this.objectSearch(searchContactParams);
returnArray.push(searchContacts);
}
return Observable.forkJoin(returnArray);
}
If I understand it correctly returnArray contains two Observables and you want to wait until they both complete but still you want to emit each result separately.
Since forkJoin emits all results in a array you could just unwrap it with mergeMap (or concatMap):
this.searchService.search(action.payload)
.pipe(
mergeMap(results => results),
map((data) => new SearchSuccess(data)),
catchError(error => of(new SearchFail(error))),
),
I'm using the WebRTC library which has a very specific API. The peerConnection.setRemoteDescription method's 2nd argument is supposed to be a callback for when it finishes setting the remote description:
This is one of my wrapper functions for my WebRTC class:
export function setRemoteSdp(peerConnection, sdp, callback) {
if (!sdp) return;
return peerConnection.setRemoteDescription(
new RTCSessionDescription(sdp),
callback, // <-------------
);
}
And this is a sketch of what I want to do:
function receivedSdp(action$, store) {
return action$.ofType(VideoStream.RECEIVED_SDP)
.mergeMap(action => {
const {peerConnection} = store.getState().videoStreams;
const {sdp} = action.payload;
return WebRTC.setRemoteSdp(peerConnection, sdp, () => {
return myReducer.myAction(); // <------ return action as the callback
})
})
};
This doesn't work since I'm not returning an Observable. Is there a way to do this?
P.S. this is the WebRTC API: https://github.com/oney/react-native-webrtc/blob/master/RTCPeerConnection.js#L176
martin's answer is correct about using Observable.create or new Observable--same thing (except it's not clear to me why you need the mergeAll() since the mergeMap will flatten?)
As a bonus, you could also use Observable.bindCallback for this.
// bindCallback is a factory factory, it creates a function that
// when called with any arguments will return an Observable that
// wraps setRemoteSdp, handling the callback portion for you.
// I'm using setRemoteSdp.bind(WebRTC) because I don't know
// if setRemoteSdp requires its calling context to be WebRTC
// so it's "just in case". It might not be needed.
const setRemoteSdpObservable = Observable.bindCallback(WebRTC.setRemoteSdp.bind(WebRTC));
setRemoteSdpObservable(peerConnection, sdp)
.subscribe(d => console.log(d));
Usage inside your epic would be something like this
// observables are lazy, so defining this outside of our epic
// is totally cool--it only sets up the factory
const setRemoteSdpObservable = Observable.bindCallback(WebRTC.setRemoteSdp.bind(WebRTC));
function receivedSdp(action$, store) {
return action$.ofType(VideoStream.RECEIVED_SDP)
.mergeMap(action => {
const {peerConnection} = store.getState().videoStreams;
const {sdp} = action.payload;
return setRemoteSdpObservable(peerConnection)
.map(result => myReducer.myAction());
})
};
You could use this to create Observable wrappers for all the WebRTC apis.
So the problem is that setRemoteSdp doesn't return an Observable while myReducer.myAction() does and that's the Observable you want to merge?
You can use Observable.create and wrap the WebRTC.setRemoteSdp call:
.mergeMap(action => {
return Observable.create(observer => {
WebRTC.setRemoteSdp(peerConnection, sdp, () => {
observer.next(myReducer.myAction());
observer.complete();
})
});
}
.mergeAll()
The Observable.create returns an Observable that emits another Observable from myReducer.myAction(). Now I have in fact so-called higher-order that I want to flatten using mergeAll() (concatAll would work as well).
I'm trying to test my asyn thunk middleware function using mocha, chai and sinon (my first time!).
Please consider my files:
ayncActionCreators.js
export const fetchCurrentUser = () => {
return (dispatch) => {
setTimeout(dispatch, 100);
}
};
ayncActionCreators.spec.js
//...
it('Should work', () => {
const dispatch = sinon.spy();
const action = fetchCurrentUser();
action(dispatch);
expect(dispatch.called).to.be.true;
});
I did not yet implement the fetchCurrentUser function - just assumed it will take some "server" time and then it will call 'dispatch()'.
The spec fails, due to the async flow. If I add a setTimeout of 101 ms before the expect - it passes.
My code will use some DB API that returns promise, so the async function will eventually look like:
//...
return (dispatch) => {
return dbAPI.fetchUser().then(dispatch(....));
}
So I tried to require dbAPI and create a sinon.stub().returns(Promise.resolve()) inside the test and it didn't work as well (I thought that since the stub returns a resolved promise - the async function will act like a synchronous function).
Any ideas how should I test async functions like that?
Thank,
Amit.
Don't mock dispatch with sinon, write your own and call Mocha's done() in that when it's done.
it('Should work', (done) => {
const dispatch = () => {
// Do your tests here
done();
};
const action = fetchCurrentUser();
action(dispatch)
// Also allow quick failures if your promise fails
.catch(done);
})
If you're just wanting to ensure that the dispatch is called, then mocha will time out. The catch on the returned promise from your async action creator allows errors to be shown in the right place and for the test to fail rather than time out.
Well, I think I've found a solution:
Assuming my async function looks like this:
//...
return (dispatch) => {
return dbAPI.fetchUser().then(dispatch(....));
}
Then I can write the spec as follows:
it('Should work', () => {
dbAPI.fetchUser = sinon.stub().returns(Promise.resolve({username: 'John'}));
const dispatch = sinon.spy();
const action = fetchCurrentUser();
action(dispatch).then(() => {
expect(dispatch.called).to.be.true;
});
});
I don't know if this is a workaround or not, but it works. I would appreciate your opinions of a better way of doing this...
Thanks,
Amit.