NAME

Mojo::IOLoop::Delay - Manage callbacks and control the flow of events

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 {
      my $delay = shift;
      Mojo::IOLoop->timer(2 => $delay->begin);
      say 'Second step in 2 seconds.';
    },

    # Second step (concurrent timers)
    sub {
      my ($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 {
      my ($delay, @args) = @_;
      say 'And done after 5 seconds total.';
    }
  )->wait;

  # Handle exceptions in all steps
  Mojo::IOLoop::Delay->new->steps(
    sub {
      my $delay = shift;
      die 'Intentional error';
    },
    sub {
      my ($delay, @args) = @_;
      say 'Never actually reached.';
    }
  )->catch(sub {
    my ($delay, $err) = @_;
    say "Something went wrong: $err";
  })->wait;

DESCRIPTION

Mojo::IOLoop::Delay manages callbacks and controls the flow of events for Mojo::IOLoop, which can help you avoid deep nested closures that often result from continuation-passing style.

EVENTS

Mojo::IOLoop::Delay inherits all events from Mojo::EventEmitter and can emit the following new ones.

error

  $delay->on(error => sub {
    my ($delay, $err) = @_;
    ...
  });

Emitted if an exception gets thrown in one of the steps, breaking the chain, fatal if unhandled.

finish

  $delay->on(finish => sub {
    my ($delay, @args) = @_;
    ...
  });

Emitted once the event counter reaches zero and there are no more steps.

ATTRIBUTES

Mojo::IOLoop::Delay implements the following attributes.

ioloop

  my $loop = $delay->ioloop;
  $delay   = $delay->ioloop(Mojo::IOLoop->new);

Event loop object to control, defaults to the global Mojo::IOLoop singleton.

remaining

  my $remaining = $delay->remaining;
  $delay        = $delay->remaining([sub {...}]);

Remaining "steps" in chain.

METHODS

Mojo::IOLoop::Delay inherits all methods from Mojo::EventEmitter 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 callback needs to be executed when the event has completed, to decrement the event counter again. When all callbacks have been executed and the event counter reached zero, "steps" will continue.

  # Capture all arguments except for the first one (invocant)
  my $delay = Mojo::IOLoop->delay(sub {
    my ($delay, $err, $stream) = @_;
    ...
  });
  Mojo::IOLoop->client({port => 3000} => $delay->begin);
  $delay->wait;

Arguments passed to the returned callback 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 or "finish" event.

  # Capture all arguments
  my $delay = Mojo::IOLoop->delay(sub {
    my ($delay, $loop, $err, $stream) = @_;
    ...
  });
  Mojo::IOLoop->client({port => 3000} => $delay->begin(0));
  $delay->wait;

  # Capture only the second argument
  my $delay = Mojo::IOLoop->delay(sub {
    my ($delay, $err) = @_;
    ...
  });
  Mojo::IOLoop->client({port => 3000} => $delay->begin(1, 1));
  $delay->wait;

  # Capture and combine arguments
  my $delay = Mojo::IOLoop->delay(sub {
    my ($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;

data

  my $hash = $delay->data;
  my $foo  = $delay->data('foo');
  $delay   = $delay->data({foo => 'bar', baz => 23});
  $delay   = $delay->data(foo => 'bar', baz => 23);

Data shared between all "steps".

  # Remove value
  my $foo = delete $delay->data->{foo};

  # Assign multiple values at once
  $delay->data(foo => 'test', bar => 23);

pass

  $delay = $delay->pass;
  $delay = $delay->pass(@args);

Increment event counter and decrement it again right away to pass values to the next step.

  # 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.

wait

  $delay->wait;

Start "ioloop" and stop it again once an "error" or "finish" event gets emitted, does nothing when "ioloop" is already running.

SEE ALSO

Mojolicious, Mojolicious::Guides, http://mojolicious.org.

cpanm Mojolicious

perl -MCPAN -e shell
install Mojolicious