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How to create an observable of a stream of infinite items


How to create an observable of a stream of infinite items

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How to create an observable of a stream of infinite items
Tag : development , By : user187301
Date : January 11 2021, 03:32 PM

I think the issue was by ths following , Are you looking to stream data? Let's say I am trying to stream data from a database.
return Observable.using(
            () -> getQueryConnectionSubscription(sql),

            connectionSubscription -> Observable.create((subscriber) -> {

                ResultSet resultSet = connectionSubscription.getResultSet();
                int rowNumber = 0;
                while (!subscriber.isDisposed() && resultSet.next()) {

                    T row = rowMapper.mapRow(resultSet, rowNumber);
                    subscriber.onNext(row);
                }
                subscriber.onComplete();

            }),

            (queryConnectionSubscription) -> {
                queryConnectionSubscription.close();
            });

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Rxjs: updating values in observable stream with data from another observable, returning a single observable stream


Tag : javascript , By : agjimenez
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , You could use flatMap or concatMap to have one task trigger another one. You could use forkJoin to request the merges in parallel and collect the result in one place. It is not tested, but it should go like this :
pullRequestStream.concatMap(function (prlist){
  var arrayRequestMerge = prlist.map(function(pr){
    return Rx.Observable.create(function(o) {...same as your code});
  });
  return Rx.Observable.forkJoin(arrayRequestMerge)
         .do(function(arrayData){
               prlist.map(function(pr, index){pr['merge']=arrayData[index]
             })})
         .map(function(){return prlist})
})
pullRequestStream.concatMap(function (prlist){
  var arrayRequestMerge = prlist.map(function(pr, index){
    return Rx.Observable.create(function(o) {
        stash.pullRequestMerge(project, repo, pr['id'])
            .on('error', function(error) {o.onError(error)})
            .on('newPage', function(data) {
                o.onNext({data: data, index : index});
                o.onCompleted();
            }).take(1);
    });
  });
  var maxConcurrent = 2;
  Rx.Observable.from(arrayRequestMerge)
    .merge(maxConcurrent)
    .do(function(obj){
               prlist[obj.index]['merge'] = obj.data
             })})
    .map(function(){return prlist})
})

How to process first n items and remaining one differently in a observable stream


Tag : java , By : Helpful Dude
Date : March 29 2020, 07:55 AM
Hope that helps You can share your m's stream, and then merge back together take() and skip() streams, something like this:
    int m = 10;
    int n = 8;
    Observable<Integer> numbersStream = Observable.just(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
            .publish();

    Observable<Integer> firstNItemsStream = numbersStream.take(n)
            .map(i -> i * 2);

    Observable<Integer> remainingItemsStream = numbersStream.skip(n)
            .map(i -> i * 3);

    Observable.merge(firstNItemsStream, remainingItemsStream)
            .subscribe(integer -> System.out.println("result = " + integer));
    numbersStream.connect();

Rx.Observable validate items in stream (pass or throw)


Tag : development , By : Simone
Date : March 29 2020, 07:55 AM
I hope this helps . Given an Stream within an Observable, I want to validate/check each item. In case one is broken I want to throw an error via Observable.throw, hence break all further processing. , You can use just normal map and throw an exception inside it:
inputStream.map(item => {
  if (isValid(item)) {
    return item;
  }
  throw new Error("not valid");
})

How to create Observable<Integer> from infinite Stream<Integer> using RxJava2?


Tag : java , By : gorbiz
Date : March 29 2020, 07:55 AM
will help you Use the generate() function:
this is kotlin code (an extension function), but you just need to change the lambda slightly. And this works with any stream.
fun <T> Stream<T>.toFlowable(): Flowable<T> {
  return Flowable.generate(
    Callable { iterator() },
    BiConsumer { ite, emitter ->
      if (ite.hasNext()) {
        emitter.onNext(ite.next())
      } else {
        emitter.onComplete()
      }
    }
  )
}
fun <T> Stream<T>.toObservable(): Observable<T> {
  return Observable.generate(
    Callable { iterator() },
    BiConsumer { ite, emitter ->
      if (ite.hasNext()) {
        emitter.onNext(ite.next())
      } else {
        emitter.onComplete()
      }
    }
  )
}
public <T> Observable<T> streamToObservable(Stream<T> stream) {
  return Observable.generate(
    () -> stream.iterator(),
    (ite, emitter) -> {
      if (ite.hasNext()) {
        emitter.onNext(ite.next());
      } else {
        emitter.onComplete();
      }
    }
  );
}
private Observable<Integer> numbers() {
    Stream<Integer> intStream = Stream.iterate(0, p -> p + 1);
    return streamToObservable(intStream);
}

How can I create a stream where the items are based on items that the stream previously returned?


Tag : development , By : wpoch
Date : March 29 2020, 07:55 AM
help you fix your problem By (ab)using async / await, the genawaiter crate manages to mimic generator syntax in stable Rust today. Combined with futures::pin_mut to pin value on the stack, here is a solution both allocation-free and compatible with arbitrary streams:
//# futures = "0.3"
//# genawaiter = { version = "0.2", features = ["futures03"] }
//# tokio = { version = "0.2", features = ["full"] }
use futures::{
    pin_mut,
    stream::{self, Stream, StreamExt},
};
use genawaiter::{generator_mut, stack::Co};
use std::collections::VecDeque;

async fn g(n: i32, co: Co<'_, i32>) {
    let mut seeds = VecDeque::from(vec![n]);
    while let Some(seed) = seeds.pop_back() {
        let stream = f(seed);
        pin_mut!(stream);
        while let Some(x) = stream.next().await {
            if x % 2 != 0 {
                seeds.push_front(x);
            }
            co.yield_(x).await;
        }
    }
}

fn f(n: i32) -> impl Stream<Item = i32> {
    stream::iter((0..n).rev())
}

#[tokio::main]
async fn main() {
    generator_mut!(stream, |co| g(5, co));
    stream
        .for_each(|v| async move {
            println!("v: {}", v);
        })
        .await;
}
use futures::{
    pin_mut,
    stream::{Stream, StreamExt},
};
use genawaiter::rc::Gen;
use std::collections::VecDeque;

fn g(n: i32) -> impl Stream<Item = i32> {
    Gen::new(|co| async move {
        let mut seeds = VecDeque::from(vec![n]);
        while let Some(seed) = seeds.pop_back() {
            let stream = f(seed);
            pin_mut!(stream);
            while let Some(x) = stream.next().await {
                if x % 2 != 0 {
                    seeds.push_front(x);
                }
                co.yield_(x).await;
            }
        }
    })
}
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