/ 
Ekorn-Pipeline-v0.1.2
/ Ekorn::Pipeline::Stop

NAME

Ekorn::Pipeline::Stop - end a pipeline early

SYNOPSIS

use Ekorn::Pipeline::Stop;

# In a stage of a pipeline
sub ($value) { Stop() if $done; ... }

# Stop, passing on a last value
sub ($user) { $user->{id} == $wanted ? Stop($user) : () }

# The same, without importing Stop
sub ($value) { Ekorn::Pipeline::Stop->throw if $done; ... }

DESCRIPTION

A stop is the exception that ends a pipeline early and quietly. The rest of the stage that throws it doesn't run. The values already out of the pipeline are kept, the values the stop carries go on through the stages after it, and nothing else is processed. Stages after the one that stopped, made with Ekorn::Pipeline::Gather, still have their end functions called.

FUNCTIONS

Stop

Stop();
Stop(@values);

Throws a stop carrying @values, the last values of the stage that throws it. It's the same as Ekorn::Pipeline::Stop->throw(@values), and is exported by default.

To keep it out of your namespace:

use Ekorn::Pipeline::Stop ();

METHODS

throw

Ekorn::Pipeline::Stop->throw;
Ekorn::Pipeline::Stop->throw(@values);
My::Stop->throw(@values);

Throws a stop carrying @values, blessed into the class it was called on, so a subclass of Ekorn::Pipeline::Stop throws one of its own.

THE STOP

A stop is an array reference, blessed into its class. Its first element is that class, and the rest are the values it was thrown with:

eval { Ekorn::Pipeline::Stop->throw(1, 2) };
my $stop = $@;    # bless ['Ekorn::Pipeline::Stop', 1, 2], 'Ekorn::Pipeline::Stop'

A pipeline sends the values on through the stages after the one that threw it, as that stage's last values.

As a string, a stop is "Stop used outside a pipeline", with a newline, which is what a user sees if one is thrown with nothing to catch it.

A stop that isn't an array, made without throw, as by blessing a hash into the class, still stops the pipeline, but carries nothing.

Catching errors in a stage

A pipeline recognises a stop with isa, so a subclass of Ekorn::Pipeline::Stop stops it too. A stage that catches errors itself, with eval or try, should throw a stop on again:

sub ($value) {
    try { ... }
    catch ($e) {
        die $e if $e isa 'Ekorn::Pipeline::Stop';
        ...
    }
}

DIAGNOSTICS

Stop used outside a pipeline

A stop was thrown where no pipeline was running to catch it.

SEE ALSO

Ekorn::Pipeline, Ekorn::Pipeline::Gather

AUTHOR

Iain Campbell <cpanic@cpan.org>

LICENSE

Copyright (c) 2024-2026 by Iain Campbell.

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