NAME
Mojo::IOLoop::Delay - (DISCOURAGED) Promises/A+ and flow-control
helpers
SYNOPSIS
use Mojo::IOLoop::Delay;
# Synchronize multiple non-blocking operations
my $delay = Mojo::IOLoop::Delay->new;
$delay->steps(sub { say 'BOOM!' });
for my $i (1 .. 10) {
my $end = $delay->begin;
Mojo::IOLoop->timer($i => sub {
say 10 - $i;
$end->();
});
}
$delay->wait;
# Sequentialize multiple non-blocking operations
Mojo::IOLoop::Delay->new->steps(
# First step (simple timer)
sub ($delay) {
Mojo::IOLoop->timer(2 => $delay->begin);
say 'Second step in 2 seconds.';
},
# Second step (concurrent timers)
sub ($delay, @args) {
Mojo::IOLoop->timer(1 => $delay->begin);
Mojo::IOLoop->timer(3 => $delay->begin);
say 'Third step in 3 seconds.';
},
# Third step (the end)
sub ($delay, @args) {
say 'And done after 5 seconds total.';
}
)->wait;
DESCRIPTION
Mojo::IOLoop::Delay adds flow-control helpers to Mojo::Promise, which
can help you avoid deep nested closures that often result from
continuation-passing style.
use Mojo::IOLoop;
# These deep nested closures are often referred to as "Callback Hell"
Mojo::IOLoop->timer(3 => sub ($loop) {
say '3 seconds';
Mojo::IOLoop->timer(3 => sub ($loop) {
say '6 seconds';
Mojo::IOLoop->timer(3 => sub ($loop) {
say '9 seconds';
Mojo::IOLoop->stop;
});
});
});
Mojo::IOLoop->start;
The idea behind Mojo::IOLoop::Delay is to turn the nested closures
above into a flat series of closures. In the example below, the call to
"begin" creates a code reference that we can pass to "timer" in
Mojo::IOLoop as a callback, and that leads to the next closure in the
series when executed.
use Mojo::IOLoop;
use Mojo::IOLoop::Delay; # adds Mojo::IOLoop->delay
# Instead of nested closures we now have a simple chain of steps
my $delay = Mojo::IOLoop->delay(
sub ($delay) { Mojo::IOLoop->timer(3 => $delay->begin) },
sub ($delay) {
say '3 seconds';
Mojo::IOLoop->timer(3 => $delay->begin);
},
sub ($delay) {
say '6 seconds';
Mojo::IOLoop->timer(3 => $delay->begin);
},
sub ($delay) { say '9 seconds' }
);
$delay->wait;
Another positive side effect of this pattern is that we do not need to
call "start" in Mojo::IOLoop and "stop" in Mojo::IOLoop manually,
because we know exactly when our chain of "steps" has reached the end.
So "wait" in Mojo::Promise can stop the event loop automatically if it
had to be started at all in the first place.
DISCOURAGED! WARNING!
This module has been extracted from Mojolicious and was removed from it
at the 9.0 release. It is kept here for backwards compatibility
purposes but there is no intention to maintain it further and it should
be migrated away from as your earliest convenience.
Though there is no intention of removing it from CPAN in the future it
should be treated as deprecated and the metadata will mark it as such.
It will receive no no-security-related changes going forward.
MOJO::IOLOOP CLASS METHOD CONSTRUCTOR
As of Mojolicious 9.0, the package Mojo::IOLoop no longer provides a
class constructor for delays. If you want to use Mojo::IOLoop->delay
you must first load this class explicitly which will add it back. You
can also use -MMojo::IOLoop::Delay at the command line to do so.
ATTRIBUTES
Mojo::IOLoop::Delay inherits all attributes from Mojo::Promise.
METHODS
Mojo::IOLoop::Delay inherits all methods from Mojo::Promise and
implements the following new ones.
begin
my $cb = $delay->begin;
my $cb = $delay->begin($offset);
my $cb = $delay->begin($offset, $len);
Indicate an active event by incrementing the event counter, the
returned code reference can be used as a callback, and needs to be
executed when the event has completed to decrement the event counter
again. When all code references generated by this method have been
executed and the event counter has reached zero, "steps" will continue.
# Capture all arguments except for the first one (invocant)
my $delay = Mojo::IOLoop->delay(sub ($delay, $err, $stream) { ... });
Mojo::IOLoop->client({port => 3000} => $delay->begin);
$delay->wait;
Arguments passed to the returned code reference are spliced with the
given offset and length, defaulting to an offset of 1 with no default
length. The arguments are then combined in the same order "begin" was
called, and passed together to the next step.
# Capture all arguments
my $delay = Mojo::IOLoop->delay(sub ($delay, $loop, $err, $stream) { ... });
Mojo::IOLoop->client({port => 3000} => $delay->begin(0));
$delay->wait;
# Capture only the second argument
my $delay = Mojo::IOLoop->delay(sub ($delay, $err) { ... });
Mojo::IOLoop->client({port => 3000} => $delay->begin(1, 1));
$delay->wait;
# Capture and combine arguments
my $delay = Mojo::IOLoop->delay(sub ($delay, $three_err, $three_stream, $four_err, $four_stream) { ... });
Mojo::IOLoop->client({port => 3000} => $delay->begin);
Mojo::IOLoop->client({port => 4000} => $delay->begin);
$delay->wait;
pass
$delay = $delay->pass;
$delay = $delay->pass(@args);
Shortcut for passing values between "steps".
# Longer version
$delay->begin(0)->(@args);
steps
$delay = $delay->steps(sub {...}, sub {...});
Sequentialize multiple events, every time the event counter reaches
zero a callback will run, the first one automatically runs during the
next reactor tick unless it is delayed by incrementing the event
counter. This chain will continue until there are no remaining
callbacks, a callback does not increment the event counter or an
exception gets thrown in a callback. Finishing the chain will also
result in the promise being fulfilled, or if an exception got thrown it
will be rejected.
SEE ALSO
Mojolicious, Mojolicious::Guides,
https://mojolicious.org.
AUTHORS
The "AUTHORS" in Mojolicious
CONTACT
While this module is no longer receiving non-security related
maintenance, if you must contact someone about it please contact Joel
Berger <
[email protected]> or as a last resort contact the Mojolicious
Core Team.
COPYRIGHT AND LICENSE
Copyright (C) 2008-2021, Sebastian Riedel and others.
This program is free software, you can redistribute it and/or modify it
under the terms of the Artistic License version 2.0.
