NAME

Promises::Sub - Turns functions into promises

VERSION

version 1.04

SYNOPSIS

use Promises 'deferred';
use parent 'Promises::Sub';

sub shall_concat :Defer {
    join ' ', @_;
}

my @promises = map { deferred } 1..2;

my @results = (
    shall_concat( @promises ),
    shall_concat( 'that is', $promises[1] ),
    shall_concat( 'this is', 'straight up' ),
);

say "all results are promises";

$_->then(sub { say @_ } ) for @results;
# prints 'this is straight up'

say "two results are still waiting...";

$promises[1]->resolve( 'delayed' );
# prints 'this is delayed'

say "only one left...";

$promises[0]->resolve( 'finally the last one, that was' );
# prints 'finally the last one, that was delayed'

DESCRIPTION

Any function tagged with the :Defer will be turned into a promise, so you can do

sub add :Defer { $_[0] + $_[1] }

add( 1,2 )->then(sub { say "the result is ", @_ } );

Additionally, if any of the arguments to the functions are promises themselves, the function call will wait until those promises are fulfilled before running.

my $number = deferred;

add( 1, $number )->then(sub { say "result: ", @_ } );

# $number is not fulfilled yet, nothing is printed

$number->resolve(47);
# prints 'result: 48'

Bear in mind that to use the :Defer attribute, you have to do use parent 'Promises::Sub';, and not use Promises::Sub; in the target namespace.

Anonymous functions

The :Defer attribute won't work for anonymous functions and will throw an exception. For those, you can export the function defer, which will wrap any coderef the same way that :Defer does.

use Promises::Sub qw/ defer /;

my $promised_sub = defer sub {
    join ' ', @_;
};

my $p1 = deferred;

$promised_sub->( 'hello', $p1 )->then( sub {
    say shift;
} );

# prints nothing

$p1->resolve('world');
# => prints 'hello world'

AUTHOR

Stevan Little <stevan.little@iinteractive.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2020, 2019, 2017, 2014, 2012 by Infinity Interactive, Inc.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.