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25 PAUSE users
15 non-PAUSE users.

Yanick Champoux
and 21 contributors

NAME

Promises::Sub - Turns functions into promises

VERSION

version 1.03

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.