I have a function called fetch which is implemented like this:
fetch(): Observable<Option> {
return this.clientNotebookService.getClientNotebook()
.pipe(
map(
clientNotebook => {
this.person = _.find(clientNotebook.persons, i => i.isn === this.isn);
return {
value: this.person.address['TownIsn'],
name: this.person.address['TownName']
};
}
)
);
}
where person is of type RelatedPerson and isn if of type string. The problem with this function is that it doesn't know anything about isn, that's to say, isn should be provided to it in some way.
This value can be extracted in the following way:
this.activatedRoute.params.subscribe(
params => this.isn = params['id']
)
And I would like to do this within the fetch method by combining rxjs operators.
You can chain them like below, just extract the 'id' and pass it to fetch
const isn=this.activatedRoute.params.pipe(pluck('id'))
isn.pipe(mergeMap(isn=>fetch(isn)))
Then add a param to your fetch, then it is available inside the function
fetch(isn){ .....
You can use combineLatest that emits an array of the latest value from both streams every time either emit a value
combineLatest(
this.activatedRoute.params.pipe(map(params => params['id'])),
this.clientNotebookService.getClientNotebook()
).pipe(map(([isn, clientNotebook]) => {
this.person = clientNotebook.persons.find(p => p.isn === isn); // No need for _
return {
value: this.person.address['TownIsn'],
name: this.person.address['TownName']
};
}));
Related
I have a collection, where each single document have an array of references.
The structure in Firestore is like this:
collection1
doc1
doc2
doc3
name: string
...
refs: Array
collection2/x786123nd...
collection2/z1237683s...
...
I want to convert that into:
[
{<doc1 as object>},
{<doc2 as object},
{ name: "Document 3", refsResult:
[
{<object here mapped from reference>},
{<object here mapped from reference>},
]
}
]
Long story short, from firebase I need to get an output of a list of object where each object has a list of objects instead of references.
THE FOLLOWING SNIPPET IS NOT WORKING
I am trying to do it at service level in Angular using RxJS to transform the output, something like this:
return this.afs.collection('collection1')
.valueChanges()
.pipe(
switchMap(objects => from(objects).pipe(
switchMap(obj => from(obj.refs).pipe(
switchMap(ref => ref.get()),
map(r => ({ ...obj, refsResult: r.data() })),
tap(obj => console.log('OBJ', obj)),
)),
)),
tap(objects => console.log(objects))
);
But it seems that I only receive one object instead of a list of objects with 2. Also, it seems that the refsResult is also a single object instead of an array. I am sure I am using the switchMaps wrong, probably they are cancelling the others results or similar.
I would like to keep the solution within the chain of rxjs operators.
EDIT 1
I got it working in a hacky way, I am just sharing it here in order to give more context, and see if we can find a way to do it with RxJS.
return this.afs.collection('collection1')
.valueChanges()
.pipe(
tap(objects => {
objects.forEach(object => {
object.refsResult = [];
object.refs.forEach(ref => {
ref.get().then(d => object.refsResult.push(d.data()));
})
})
}),
tap(programs => console.log(programs))
);
The code above works but not very well, since first return the collection and then, mutates the objects to inject the items within the array. Hopefully it helps.
Help is very appreciated! :)
You can use combineLatest to create a single observable that emits an array of data.
In your case, we can use it twice in a nested way:
to handle each object in collection
to handle each ref in refs array for each object
The result is a single observable that emits the full collection of objects, each with their full collection of ref result data. You then only need a single
switchMap to handle subscribing to this single observable:
return this.afs.collection('collection1').valueChanges().pipe(
switchMap(objects => combineLatest(
objects.map(obj => combineLatest(
obj.refs.map(ref => from(ref.get()).pipe(map(r => r.data())))
).pipe(
map(refsResult => ({ ...obj, refsResult }))
)
))
))
);
For readability, I'd probably create a separate function:
function appendRefData(obj) {
return combineLatest(
obj.refs.map(ref => ref.get().pipe(map(r => r.data())))
).pipe(
map(refsResult => ({ ...obj, refsResult }))
);
}
return this.afs.collection('collection1').valueChanges().pipe(
switchMap(objects => combineLatest(objects.map(appendRefData)))
);
I use the following method in odder to retrieve data by passing pageIndex (1) and pageSize (500) for each HTTP call.
this.demoService.geList(1, 500).subscribe(data => {
this.data = data.items;
});
The response has a property called isMore and I want to modify my method in odder to continue HTTP calls if isMore is true. I also need to merge the returned values and finally return the accumulated values.
For example, assuming that there are 5000 records and until 10th HTTP call, the service returns true for isMore value. After 10th HTTP call, it returns false and then this method sets this.data value with the merged 5000 records. For this problem, should I use mergeMap or expand or another RxJs operator? What is the proper way to solve this problem?
Update: I use the following approach, but it does not merge the returned values and not increase the pageIndex. For this reason it does not work (I tried to make some changes, but could not make it work).
let pageIndex = 0;
this.demoService.geList(pageIndex+1, 500).pipe(
expand((data) => {
if(data.isComplete) {
return of(EMPTY);
} else {
return this.demoService.geList(pageIndex+1, 500);
}
})
).subscribe((data) => {
//your logic here
});
Update II:
of({
isMore : true,
pageIndex: 0,
items: []
}).pipe(
expand(data => demoService.geList(data.pageIndex+1, 100)
.pipe(
map(newData => ({...newData, pageIndex: data.pageIndex+1}))
)),
// takeWhile(data => data.isMore), //when using this, it does not work if the total record is less than 100
takeWhile(data => (data.isMore || data.pageIndex === 1)), // when using this, it causing +1 extra HTTP call unnecessarily
map(data => data.items),
reduce((acc, items) => ([...acc, ...items]))
)
.subscribe(data => {
this.data = data;
});
Update III:
Finally I made it work by modifying Elisseo's approach as shown below. Howeveri **I need to make it void and set this.data parameter in this getData() method. How can I do this?
getData(pageIndex, pageSize) {
return this.demoService.geList(pageIndex, pageSize).pipe(
switchMap((data: any) => {
if (data.isMore) {
return this.getData(pageIndex+1, pageSize).pipe(
map((res: any) => ({ items: [...data.items, ...res.items] }))
);
}
return of(data);
})
);
}
I want to merge the following subscribe part to this approach but I cannot due to some errors e.g. "Property 'pipe' does not exist on type 'void'."
.subscribe((res: any) => {
this.data = res;
});
getData(pageIndex, pageSize) {
return this.demoService.getList(pageIndex, pageSize).pipe(
switchMap((data: any) => {
if (!data.isCompleted) {
return this.getData(pageIndex+1, pageSize).pipe(
map((res: any) => ({ data: [...data.data, ...res.data] }))
);
}
return of(data);
})
);
}
stackblitz
NOTE: I updated pasing as argument pageIndex+1 as #mbojko suggest -before I wrote pageIndex++
UPDATE 2
Using expand operator we need take account that we need feed the "recursive function" with an object with pageIndex -it's necesarry in our call- for this, when we make this.demoService.getList(data.pageIndex+1,10) we need "transform the result" adding a new property "pageIndex". for this we use "map"
getData() {
//see that initial we create "on fly" an object with properties: pageIndex,data and isCompleted
return of({
pageIndex:1,
data:[],
isCompleted:false
}).pipe(
expand((data: any) => {
return this.demoService.getList(data.pageIndex,10).pipe(
//here we use map to create "on fly" and object
map((x:any)=>({
pageIndex:data.pageIndex+1, //<--pageIndex the pageIndex +1
data:[...data.data,...x.data], //<--we concatenate the data using spread operator
isCompleted:x.isCompleted})) //<--isCompleted the value
)
}),
takeWhile((data: any) => !data.isCompleted,true), //<--a take while
//IMPORTANT, use "true" to take account the last call also
map(res=>res.data) //finally is we only want the "data"
//we use map to return only this property
)
}
Well we can do a function like this:
getData() {
of({pageIndex:1,data:[],isCompleted:false}).pipe(
expand((data: any) => {
return this.demoService.getList(data.pageIndex,10).pipe(
tap(x=>{console.log(x)}),
map((x:any)=>({
pageIndex:data.pageIndex+1,
data:[...data.data,...x.data],
isComplete:x.isComplete}))
)
}),
takeWhile((data: any) => !data.isComplete,true), //<--don't forget the ",true"
).subscribe(res=>{
this.data=res.data
})
}
See that in this case we don't return else simple subscribe to the function and equal a variable this.data to res.data -it's the reason we don't need the last map
Update 3 by Mrk Sef
Finally, if you don't want your stream to emit intermittent values and you just want the final concatenated data, you can remove the data concatenation from expand, and use reduce afterward instead.
getData() {
of({
pageIndex: 1,
data: [],
isCompleted: false
})
.pipe(
expand((prevResponse: any) => this.demoService.getList(prevResponse.pageIndex, 10).pipe(
map((nextResponse: any) => ({
...nextResponse,
pageIndex: prevResponse.pageIndex + 1
}))
)
),
takeWhile((response: any) => !response.isCompleted, true),
// Keep concatenting each new array (data.items) until the stream
// completes, then emit them all at once
reduce((acc: any, data: any) => {
return [...acc, ...data.data];
}, [])
)
.subscribe(items => {
this.data=items;
});
}
It doesn't matter if you're total record change as long as api response give you the isMore flag.
I'm skipping the part how to implement reducer action event i'm assuming you've already done that part. So i will just try to explain with pseudo codes.
You have a table or something like that with pagination data. on intial state you can just create an loadModule effect or using this fn:
getPaginationDataWithPageIndex(pageIndex = 1){
this.store.dispatch(new GetPaginationData({ pageIndex: pageIndex, dataSize: 500}));
}
in your GetPaginationData effect
... map(action => {
return apicall.pipe(map((response)=> {
if(response.isMore){
return new updateState({data:response.data, isMore: responseisMore})
} else {
return new updateState({isMore: response.isMore}),
}
}})
`
all you have to left is subscribing store in your .ts if isMore is false you will not display the next page button. and on your nextButton or prevButton's click method you should have to just dispatch the action with pageIndex
I do not think recursion is the correct approach here:
interval(0).pipe(
map(count => this.demoService.getList(count + 1, 500)),
takeWhile(reponse => response.isMore, true),
reduce((acc, curr) => //reduce any way you like),
).subscribe();
This should make calls to your endpoint until the endpoint returns isMore === false. The beautiful thing about interval is that we get the count variable for free.
But if you are set on using recrsion, here is the rxjs-way to do that using the expand-operator (see the docs). I find it slightly less readable, as it requires an if-else-construct which increases code complexity. Also the outer 'counter' variable just isn't optimal.
let index = 1;
this.demoService.geList(index, 500).pipe(
expand(response => response.isMore ? this.demoService.geList(++index, 500) : empty()),
reduce((acc, curr) => //reduce here)
).subscribe();
I have following function:
this.localStorage.getItem('user').subscribe(user => {
this.user = user;
this.authSrv.getOrders(this.user.einsender).pipe(map(orders => {
map(order => { order["etz"] = "23"; return order})
return orders;
})).subscribe(orders => {
this.orders = orders;
this.completeOrders = orders;
console.log(orders);
this.waitUntilContentLoaded = true;
})
})
The result without the map is:
[{id: 1, etz: "21"}]
With the map from above I try to enter the array, then the order and in the order I try to change the etz property but somehow nothing changes. Can someone look over?
I appreciate any help!
I see multiple issues here.
Try to avoid nested subscriptions. Instead you could use one of the RxJS higher order mapping operators like switchMap. You could find differences b/n different higher order mapping operators here and here.
To adjust each element of the array you need to use Array#map method in addition to the RxJS map operator.
You could use JS spread operator to adjust some of the properties of the object and retain other properties.
Try the following
this.localStorage.getItem('user').pipe(
switchMap(user => {
this.user = user;
return this.authSrv.getOrders(this.user.einsender).pipe(
map(orders => orders.map(order => ({...order, order['etz']: '23'})))
});
})
).subscribe(
orders => {
this.orders = orders;
this.completeOrders = orders;
console.log(orders);
this.waitUntilContentLoaded = true;
},
error => {
// good practice to handle HTTP errors
}
);
map is an operator that goes in a pipe like this:
someObs$.pipe(map(arg => { return 'something'}));
You've done this:
someObs$.pipe(map(arg => {
map(arg => { return 'something' }) // this line here does nothing
return arg;
}));
It doesn't make any sense to use map inside the function you've given to map
I am trying to inject the value of {clickedYear} into my filter function so that I can use the information dynamically.
How can I pull the value from the {clickedYear} so that the response from the API is sorted properly within an array? On the console.log the information is there in a string but it's not working within the function. The sorting doesn't work and returns an empty array...
here is my code:
const InformationBoxLayout = ({ clickedYear }) => {
const [activeYear, setActiveYear] = useState([]);
useEffect(() => {
axios
.get('http://www.mocky.io/v2/5ea446a43000005900ce2ca3')
.then((response) =>
setActiveYear(
response.data.timelineInfo.filter(
(item) => item.year === { clickedYear }
)
)
);
}, []);
return (...some code...)
You don't need {} around clickedYear when you're not in a JSX expression, which you aren't in the filter callback. So:
setActiveYear(
response.data.timelineInfo.filter(
(item) => item.year === clickedYear
// −−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^^
)
)
The reason it wasn't working is that { clickedYear } is an object literal creating an object with a clickedYear property (it's shorthand property notation for { clickedYear: clickedYear }). An object will never be === a string (I see in the JSON that year is a string). Also ensure that clickedYear is a string, not a number, since again you're using === which will never be true for different types.
A second thing you need to do is pass clickedYear as a dependency to your useEffect hook, since you use its value within it:
useEffect(() => {
axios
.get('http://www.mocky.io/v2/5ea446a43000005900ce2ca3')
.then((response) =>
setActiveYear(
response.data.timelineInfo.filter(
(item) => item.year === clickedYear
// −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^
)
)
);
}, [clickedYear]);
// ^^^^^^^^^^^^^
Without that dependency, your effect callback will only be triggered once. With it, it will be triggered each time clickedYear changes.
Side note: If you like, you can use destructuring in the filter callback:
setActiveYear(
response.data.timelineInfo.filter(
({year}) => year === clickedYear
// −−−−−−^^^^^^−−−−−^^^^
)
)
I have two services named 'PatientsService' and 'AppointmentService'. In third service 'AppointedPatientsService', I want to subscribe to AppointmentService to get all booked appointments with patientId and after that I want to repeatedly subscribe to PatientsService.getPatient(patientId) to get Patient's data with patientId. And then, I want to return new array named allAppointedPatients which holds all appointments with patient's data. I tried this...
getAppointments() {
let allAppointments: Appointment[] = [];
const allAppointedPatients: AppointedPatient[] = [];
return this.appointmentService.fetchAllAppointments().pipe(
take(1),
tap(appointments => {
allAppointments = appointments;
for (const appointment of allAppointments) {
this.patientsService.getPatient(appointment.patientId).pipe(
tap(patient => {
const newAppointment = new AppointedPatient(patient.firstName,
patient.lastName,
patient.address,
patient.casePaperNumber,
appointment.appointmentDateTime);
allAppointedPatients.push(newAppointment);
})
).subscribe();
}
return allAppointedPatients;
}),
pipe(tap((data) => {
return this.allAppointedPatients;
}))
);
}
This is not working and I know there must be better way to handle such scenario. Please help...
You are messing up the async code (observables) with sync code by trying to return the allAppointedPatients array synchronously.
Understand first how async code is working in Javascript and also why Observables (streams) are so useful.
Try the code below and make sure you understand. Of course, I was not able to test it so make your own changes if needed.
getAppointments(): Observable<AppointedPatient[]> {
return this.appointmentService.fetchAllAppointments()
.pipe(
switchMap(appointments => {
const pacientAppointments = [];
for (const appointment of allAppointments) {
// Extract the data aggregation outside or create custom operator
const pacientApp$ = this.patientsService.getPatient(appointment.patientId)
.pipe(
switchMap((pacient) => of(
new AppointedPatient(
patient.firstName,
patient.lastName,
patient.address,
patient.casePaperNumber,
appointment.appointmentDateTime
)
))
)
pacientAppoinments.push(pacientApp$);
}
return forkJoin(pacientAppointments);
});
}
You can use forkJoin:
forkJoin(
getSingleValueObservable(),
getDelayedValueObservable()
// getMultiValueObservable(), forkJoin on works for observables that complete
).pipe(
map(([first, second]) => {
// forkJoin returns an array of values, here we map those values to an object
return { first, second };
})
);