NAME

RxPerl - an implementation of Reactive Extensions / rxjs for Perl

SYNOPSIS

    use RxPerl::AnyEvent ':all';
    use AnyEvent;

    sub make_observer ($i) {
        return {
            next     => sub {say "next #$i: ", $_[0]},
            error    => sub {say "error #$i: ", $_[0]},
            complete => sub {say "complete #$i"},
        };
    }

    my $o = rx_interval(0.7)->pipe(
        op_map(sub {$_[0] * 2}),
        op_take_until( rx_timer(5) ),
    );

    $o->subscribe(make_observer(1));

    AnyEvent->condvar->recv;

    use RxPerl::IOAsync ':all';
    use IO::Async::Loop;

    my $loop = IO::Async::Loop->new;
    RxPerl::IOAsync::set_loop($loop);

    sub make_observer ($i) {
        return {
            next     => sub {say "next #$i: ", $_[0]},
            error    => sub {say "error #$i: ", $_[0]},
            complete => sub {say "complete #$i"},
        };
    }

    my $o = rx_interval(0.7)->pipe(
        op_map(sub {$_[0] * 2}),
        op_take_until( rx_timer(5) ),
    );

    $o->subscribe(make_observer(1));

    $loop->run;

    use RxPerl::Mojo ':all';
    use Mojo::IOLoop;

    sub make_observer ($i) {
        return {
            next     => sub {say "next #$i: ", $_[0]},
            error    => sub {say "error #$i: ", $_[0]},
            complete => sub {say "complete #$i"},
        };
    }

    my $o = rx_interval(0.7)->pipe(
        op_map(sub {$_[0] * 2}),
        op_take_until( rx_timer(5) ),
    );

    $o->subscribe(make_observer(1));

    Mojo::IOLoop->start;

DESCRIPTION

This module is an implementation of Reactive Extensions in Perl. It replicates the behavior of rxjs 6 which is the JavaScript implementation of ReactiveX.

Currently 44 of the 100+ operators in rxjs are implemented in this module.

EXPORTABLE FUNCTIONS

The code samples in this section assume $observer has been set to:

    $observer = {
        next     => sub {say "next: ", $_[0]},
        error    => sub {say "error: ", $_[0]},
        complete => sub {say "complete"},
    };

OBSERVABLE CREATION OPERATORS

Creation operators create and return an observable. They are usually unicast, which means that when an "rx_interval" observable is subscribed to three seperate times there will be three different & distinct recurring intervals. Exceptions to this are with subjects and that any observable can be transformed into a multicasting one using the "op_share" pipeable operator (or by other similar operators).

The following list is the currently implemented creation operators with links to relevant rxjs documentation (which should apply to RxPerl too).

rx_combine_latest

https://rxjs.dev/api/index/function/combineLatest

    # [0, 0], [0, 1], [1, 1], [1, 2], [1, 3], ...
    rx_combine_latest([
        rx_interval(1),
        rx_interval(0.7),
    ])->subscribe($observer);

rx_concat

https://rxjs.dev/api/index/function/concat

    # 10, 20, 30, 10, 20, 30, 40, complete
    rx_concat(
        rx_of(10, 20, 30),
        rx_of(10, 20, 30, 40),
    )->subscribe($observer);

rx_defer

https://rxjs.dev/api/index/function/defer

    # Suppose "int rand 10" here evaluates to 7. Then if after 7 seconds $special_var holds a true value,
    # output will be: 0, 1, 2, 3, 4, 5, 6, 10, 20, 30, complete, otherwise it will be:
    # 0, 1, 2, 3, 4, 5, 6, 40, 50, 60, complete.

    rx_concat(
        rx_interval(1)->pipe( op_take(int rand 10) ),
        rx_defer(sub {
            return $special_var ? rx_of(10, 20, 30) : rx_of(40, 50, 60)
        })
    )->subscribe($observer);

rx_EMPTY

https://rxjs.dev/api/index/const/EMPTY

    # complete
    rx_EMPTY->subscribe($observer);

    # 10, 20, 30, 40, 50, 60, complete
    rx_concat(
        rx_of(10, 20, 30),
        rx_EMPTY,
        rx_EMPTY,
        rx_EMPTY,
        rx_of(40, 50, 60),
    )->subscribe($observer);

rx_fork_join

https://rxjs.dev/api/index/function/forkJoin

    # [30, 3, 'c']
    rx_fork_join([
        rx_of(10, 20, 30),
        rx_of(1, 2, 3),
        rx_of('a', 'b', 'c'),
    ])->subscribe($observer);

    # {x => 30, y => 3, z => 'c'}
    rx_fork_join({
        x => rx_of(10, 20, 30),
        y => rx_of(1, 2, 3),
        z => rx_of('a', 'b', 'c'),
    })->subscribe($observer);

rx_from

https://rxjs.dev/api/index/function/from

Currently, only arrayrefs, promises, observables and strings are allowed as argument to this function.

    # 10, 20, 30, complete
    rx_from([10, 20, 30])->subscribe($observer);

rx_from_event

https://rxjs.dev/api/index/function/fromEvent

Currently, only instances of the Mojo::EventEmitter class are allowed as the first argument to this function.

    # 4 seconds after Mojolicious hypnotoad is gracefully reloaded, websocket
    # connection will close

    sub websocket ($c) {
        rx_from_event($ioloop, 'finish')->pipe(
            op_delay(4),
        )->subscribe({
            next => sub { $c->finish },
        });
    }

rx_from_event_array

https://rxjs.dev/api/index/function/fromEvent

Similar to: "rx_from_event".

Observables may emit at most one value per event, however Mojo::EventEmitter's are able to emit more. So this function serves to pack all of them in an arrayref, and emit that as a single value instead.

rx_interval

https://rxjs.dev/api/index/function/interval

Works like rxjs's "interval", except the parameter is in seconds instead of ms.

    # 0, 1, 2, ... every 0.7 seconds
    rx_interval(0.7)->subscribe($observer);

rx_merge

https://rxjs.dev/api/index/function/merge

    # 0, 0, 1, 1, 2, 3, 2, 4, 3, ...
    rx_merge(
        rx_interval(0.7),
        rx_interval(1),
    )->subscribe($observer);

rx_NEVER

https://rxjs.dev/api/index/const/NEVER

    # 10, 20, 30 (and no complete)
    rx_concat(
        rx_of(10, 20, 30),
        rx_NEVER,
        rx_of(40, 50, 60),
    )->subscribe($observer);

rx_observable

https://rxjs.dev/api/index/class/Observable

    0.578, 0.234, 0.678, ... (every 1 second)
    my $o = rx_observable->new(sub ($subscriber) {
        # your code goes here
        Mojo::IOLoop->recurring(1, sub {$subscriber->next(rand())});
    });

rx_of

https://rxjs.dev/api/index/function/of

    # 10, 20, 30, complete
    rx_of(10, 20, 30)->subscribe($observer);

rx_race

https://rxjs.dev/api/index/function/race

    # 0, 10, 20, 30, ... (every 0.7 seconds)
    rx_race(
        rx_interval(1)->pipe( op_map(sub {$_[0] * 100}) ),
        rx_interval(0.7)->pipe( op_map(sub {$_[0] * 10) ),
    )->subscribe($observer);

rx_subject

https://rxjs.dev/api/index/class/Subject

    my $subject = rx_subject->new;
    $subject->subscribe($observer);

    # elsewhere...
    $subject->next($_) for 1 .. 10;
    $subject->complete;

rx_throw_error

https://rxjs.dev/api/index/function/throwError

    # 0, 1, 2, 3, error: foo
    rx_concat(
        rx_interval(1)->pipe( op_take(4) ),
        rx_throw_error('foo'),
    )->subscribe($observer);

rx_timer

https://rxjs.dev/api/index/function/timer

Works like rxjs's "timer", except the parameter is in seconds instead of ms.

    # (pause 10 seconds) 0, 1, 2, 3, ... (every 1 second)
    rx_timer(10, 1)->subscribe($observer);

    # (pause 10 seconds) 0, complete
    rx_timer(10)->subscribe($observer);

PIPEABLE OPERATORS

Pipeable operators (also referred to as "operators") are passed as arguments to the "pipe" method of observables. Their function is to take an observable, transform it somehow, then (similar to piped shell commands) pass the result of the transformation to the next pipeable operator in the pipe, or return it to the user.

The following list is the currently implemented operators, with links to relevant rxjs documentation (which should apply to RxPerl too).

op_catch_error

https://rxjs.dev/api/operators/catchError

    # foo, foo, foo, complete
    rx_throw_error('foo')->pipe(
        op_catch_error(sub ($err, $caught) { rx_of($err, $err, $err) }),
    )->subscribe($observer);

op_concat_map

https://rxjs.dev/api/operators/concatMap

    # 0, 1, 2, 0, 1, 2, 0, 1, 2, complete
    rx_of(10, 20, 30)->pipe(
        op_concat_map(sub {
            rx_interval(1)->pipe(op_take(3)),
        }),
    )->subscribe($observer);

op_debounce_time

https://rxjs.dev/api/operators/debounceTime

Works like rxjs's "debounceTime", except the parameter is in seconds instead of ms.

    # 3, complete
    rx_of(1, 2, 3)->pipe(
        op_debounce_time(0.5),
    )->subscribe($observer);

op_delay

https://rxjs.dev/api/operators/delay

Works like rxjs's "delay", except the parameter is in seconds instead of ms.

    # (pause 11 seconds) 0, 1, 2, 3, ...
    rx_interval(1)->pipe( op_delay(10) )->subscribe($observer);

op_distinct_until_changed

https://rxjs.dev/api/operators/distinctUntilChanged

    # 10, undef, 20, 30, [], []
    rx_of(10, 10, undef, undef, 20, 20, 20, 30, 30, [], [])->pipe(
        op_distinct_until_changed(),
    )->subscribe($observer);

    # {name => 'Peter', grade => 'A'}, {name => 'Mary', grade => 'B'}, complete
    rx_of(
        {name => 'Peter', grade => 'A'},
        {name => 'Peter', grade => 'B'},
        {name => 'Mary', grade => 'B'},
        {name => 'Mary', grade => 'A'},
    )->pipe(
        op_distinct_until_changed(sub {
            return $_[0]->{name} eq $_[1]->{name};
        }),
    )->subscribe($observer);

op_distinct_until_key_changed

https://rxjs.dev/api/operators/distinctUntilKeyChanged

    # {name => 'Peter', grade => 'A'}, {name => 'Mary', grade => 'B'}, complete
    rx_of(
        {name => 'Peter', grade => 'A'},
        {name => 'Peter', grade => 'B'},
        {name => 'Mary', grade => 'B'},
        {name => 'Mary', grade => 'A'},
    )->pipe(
        op_distinct_until_key_changed('name'),
    )->subscribe($observer);

op_end_with

https://rxjs.dev/api/operators/endWith

    # 0, 1, 2, 3, 100, 200, complete
    rx_of(0, 1, 2, 3)->pipe(
        op_end_with(100, 200),
    )->subscribe($observer);

op_exhaust_map

https://rxjs.dev/api/operators/exhaustMap

    # 0, 1, 2, complete
    rx_of(10, 20, 30)->pipe(
        op_exhaust_map(sub {
            rx_interval(1)->pipe( op_take(3) );
        }),
    )->subscribe($observer);

op_filter

https://rxjs.dev/api/operators/filter

    # 0, 2, 4, 6, ... (every 1.4 seconds)
    rx_interval(0.7)->pipe(
        op_filter(sub {$_[0] % 2 == 0}),
    )->subscribe($observer);

op_finalize

https://rxjs.dev/api/operators/finalize

    # 1, 2, 3, complete, 'hi there'
    rx_of(1, 2, 3)->pipe(
        op_finalize(sub {print "hi there\n"}),
    )->subscribe($observer);

op_first

https://rxjs.dev/api/operators/first

    # (pause 7 seconds) 6, complete
    rx_interval(1)->pipe(
        op_first(sub { $_[0] > 5 }),
    )->subscribe($observer);

    # 0, complete
    rx_interval(0.7)->pipe(
        op_first(),
    )->subscribe($observer);

op_map

https://rxjs.dev/api/operators/map

    # 10, 11, 12, 13, ...
    rx_interval(1)->pipe(
        op_map(sub {$_[0] + 10}),
    )->subscribe($observer);

op_map_to

https://rxjs.dev/api/operators/mapTo

    # 123, 123, 123, ... (every 1 second)
    rx_interval(1)->pipe(
        op_map_to(123),
    )->subscribe($observer);

op_merge_map

https://rxjs.dev/api/operators/mergeMap

    # 11, 21, 31, 12, 22, 32, 13, 23, 33, complete
    rx_of(10, 20, 30)->pipe(
        op_merge_map(sub ($x) {
            return rx_interval(1)->pipe(
                op_map(sub ($y) {
                    return $x + $y + 1;
                }),
                op_take(3),
            );
        }),
    )->subscribe($observer);

op_multicast

https://rxjs.dev/api/operators/multicast

op_pairwise

https://rxjs.dev/api/operators/pairwise

    # [0, 1], [1, 2], [2, 3], ...
    rx_interval(1)->pipe(
        op_pairwise,
    )->subscribe(sub {print Dumper($_[0])});

op_pluck

https://rxjs.dev/api/operators/pluck

    # Mary, Paul, undef, undef, undef, complete
    rx_of(
        {name => {first => 'Mary'}},
        {name => {first => 'Paul'}},
        {house => {first => 'Chicago'}},
        15,
        undef,
    )->pipe(
        op_pluck('name', 'first'),
    )->subscribe($observer);

op_ref_count

https://rxjs.dev/api/operators/refCount

op_scan

https://rxjs.dev/api/operators/scan

    # 0, 1, 3, 6, 10, ...
    rx_interval(1)->pipe(
        op_scan(sub {
            my ($acc, $item) = @_;
            return $acc + $item;
        }, 0),
    )->subscribe($observer);

op_share

https://rxjs.dev/api/operators/share

    # t0, 0, 0, t1, 1, 1, t2, 2, 2, ...
    my $o = rx_interval(1)->pipe(
        op_tap(sub {say 't' . $_[0]}),
        op_share(),
    );

    $o->subscribe($observer1);
    $o->subscribe($observer2);

op_start_with

https://rxjs.dev/api/operators/startWith

    # 100, 200, 0, 1, 2, 3, complete
    rx_of(0, 1, 2, 3)->pipe(
        op_start_with(100, 200),
    )->subscribe($observer);

op_switch_map

https://rxjs.dev/api/operators/switchMap

    # 1, 2, 3, 11, 12, 13, 21, 22, 23, 24, 25, 26, 27, ...
    my $o = rx_interval(2.5)->pipe( op_take(3) );

    $o->pipe(
        op_switch_map(sub ($x) {
            return rx_interval(0.7)->pipe(
                op_map(sub ($y) { $x * 10 + $y + 1 }),
            );
        }),
    )->subscribe($observer);

op_take

https://rxjs.dev/api/operators/take

    # 0, 1, 2, 3, 4, complete
    rx_interval(1)->pipe(
        op_take(5),
    )->subscribe($observer);

op_take_until

https://rxjs.dev/api/operators/takeUntil

    # 0, 1, 2, 3, 4, complete
    rx_interval(1)->pipe(
        op_take_until( rx_timer(5.5) ),
    )->subscribe($observer);

op_take_while

https://rxjs.dev/api/operators/takeWhile

    # 0, 1, 2, 3, 4, 5, complete
    rx_interval(1)->pipe(
        op_take_while(sub { $_[0] <= 5 }),
    )->subscribe($observer);

    # 0, 1, 2, 3, 4, 5, 6, complete
    rx_interval(1)->pipe(
        op_take_while(sub { $_[0] <= 5 }, 1),
    )->subscribe($observer);

op_tap

https://rxjs.dev/api/operators/tap

    # foo0, 0, foo1, 1, foo2, 2, ...
    rx_interval(1)->pipe(
        op_tap(sub {say "foo$_[0]"}),
    )->subscribe($observer);

op_with_latest_from

https://rxjs.dev/api/operators/withLatestFrom

    # [0, 0], [1, 1], [2, 3], [3, 4], [4, 6], ...
    rx_interval(1)->pipe(
        op_with_latest_from(rx_interval(1)),
    )->subscribe($observer);

OBSERVABLE METHODS

subscribe

http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-subscribe

    $o->subscribe(
        sub {say "next: $_[0]"},
        sub {say "error: $_[0]"},
        sub {say "complete"},
    );

    $o->subscribe(
        undef,
        sub {say "error: $_[0]"},
    );

    $o->subscribe({
        next => sub {say "next: $_[0]"},
        complete => sub {say "complete"},
    });

pipe

http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-pipe

    # 2, 6, complete
    rx_interval(1)->pipe(
        op_take(5),
        op_filter(sub {$_[0] % 2 == 1}),
        op_map(sub {2 * $_[0]}),
    )->subscribe(...)

CONNECTABLE OBSERVABLE METHODS

Connectable observables are a subclass of observables, which (like Subjects) are multicasting and can start emitting even before anyone subscribes to them, by invoking a method. They are usually created and returned by the "op_multicast" pipeable operator.

connect

Makes the connectable observable start emitting.

    $o->connect;

SUBJECT METHODS

Subjects multicast, and apart from being observables themselves (with their own subscribers), also have next, error and complete methods of their own, so can be used as the observer argument to another observable's subscribe method. That observable's events will then be "forwarded" to the subject's own subscribers, as if next/error/complete had been called on the subject directly.

next, error, complete: Calling these methods manually will cause the subject's subscribers to receive the corresponding events.

Typically subjects don't emit anything on their own (as opposed to "rx_interval" et al), although it is possible to create a subclass of Subject that behaves differently. An example is a queueing subject that accumulates events from the observable it has been subscribed to, then emits all of them at once to the first subscriber that subscribes to it.

NAMING CONVENTIONS

To prevent naming collisions with Perl’s built-in functions (or the user’s own), as rxjs’s operators are often small english words (such as map), the names of this module’s operators start with rx_ or op_.

Functions that in the JS world would be imported from 'rxjs' have their corresponding RxPerl names prepended with rx_, whereas functions imported from 'rxjs/operators' (namely pipeable opreators) start with op_ in RxPerl.

    import {Observable, Subject, timer, interval} from 'rxjs';
    import {map, filter, delay} from 'rxjs/operators';

becomes:

    use RxPerl::IOAsync qw/
        rx_observable rx_subject rx_timer rx_interval
        op_map op_filter op_delay
    /;

CAVEATS

Since the rxjs implementation differs from the ReactiveX API at a few points (as do most of the Rx* libraries), RxPerl chose to behave like rxjs rather than ReactiveX to cater for web developers already familiar with rxjs.

LEARNING MATERIAL

TODO

Fix the occasional bug
Implement more operators, based on user requests

NOTIFICATIONS FOR NEW VERSIONS

You can start receiving emails for new releases of this module, at https://perlmodules.net.

LICENSE

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

AUTHOR

KARJALA Corp <karjala@cpan.org>

To install RxPerl, copy and paste the appropriate command in to your terminal.

cpanm

cpanm RxPerl

CPAN shell

perl -MCPAN -e shell
install RxPerl

For more information on module installation, please visit the detailed CPAN module installation guide.

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