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 26 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: ", $_[0]},
complete => sub {say "complete"},
};
OBSERVABLE CREATION OPERATORS
Creation operators create and return an observable. They are usually unicast, which means that when an "rx_interval" observable is subscribed to three seperate times there will be three different & distinct recurring intervals. Exceptions to this are with subjects, and that any observable can be transformed into a multicasting one using the "op_share" pipeable operator (or by other similar operators).
The following list is the currently implemented creation operators with links to relevant rxjs documentation (which should apply to RxPerl too).
-
rx_concat
https://rxjs.dev/api/index/function/concat
# 10, 20, 30, 10, 20, 30, 40, complete rx_concat( rx_of(10, 20, 30), rx_of(10, 20, 30, 40), )->subscribe($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_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, 2, 3, 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_delay
https://rxjs.dev/api/operators/delay
Works like rxjs's "delay", except the parameter is in seconds instead of ms.
# (pause 10 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($observer); -
op_filter
https://rxjs.dev/api/operators/filter
# 0, 2, 4, 6, ... (every 1.4 seconds) rx_interval(0.7)->pipe( op_filter(sub {$_[0] % 2 == 0}), )->subscribe($observer); -
op_first
https://rxjs.dev/api/operators/first
# (pause 7 seconds) 6, complete rx_interval( op_first(sub { $_[0] > 5 }), )->subscribe($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($observer); -
op_merge_map
https://rxjs.dev/api/operators/mergeMap
# 11, 21, 31, 12, 22, 32, 13, 23, 33 rx_of(10, 20, 30)->pipe( op_merge_map(sub ($x) { return rx_interval(1)->pipe( op_map(sub ($y) { return $x + $y + 1; }), op_take(3), ); }), )->subscribe($observer); -
op_multicast
-
op_pairwise
https://rxjs.dev/api/operators/pairwise
# [0, 1], [1, 2], [2, 3], ... rx_interval(1)->pipe( op_pairwise, )->subscribe(sub {print Dumper($_[0])}); -
op_ref_count
-
op_scan
https://rxjs.dev/api/operators/scan
# 0, 1, 3, 6, 10, ... rx_interval(1)->pipe( op_scan(sub { my ($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);
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: $_[0]"}, complete => sub {say "complete"}, }); -
pipe
http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-pipe
# 2, 6 rx_interval(1)->pipe( op_take(5), op_filter(sub {$_[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
SEE ALSO
NOTIFICATIONS FOR NEW VERSIONS
You can start receiving emails for new releases of this module, at https://perlmodules.net.
LICENSE
Copyright (C) Karelcom OÜ.
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