Sebastian Riedel > Mojolicious > Mojo::IOLoop::Delay

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NAME ^

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

SYNOPSIS ^

  use Mojo::IOLoop::Delay;

  # Synchronize multiple events
  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 events
  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 and memory leaks 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 error occurs in one of the steps, breaking the chain, fatal if unhandled.

finish

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

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

ATTRIBUTES ^

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

ioloop

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

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

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);

Increment active event counter, the returned callback can be used to decrement the active event counter again. Arguments passed to the callback are spliced and queued in the right order for the next step or "finish" event and "wait" method, the argument offset defaults to 1 with no default length.

  # 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;

  # 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;

data

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

Data shared between all "steps".

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

pass

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

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

  # Longer version
  $delay->begin(0)->(@args);

remaining

  my $remaining = $delay->remaining;
  $delay        = $delay->remaining([]);

Remaining "steps" in chain, stored outside the object to protect from circular references.

steps

  $delay = $delay->steps(sub {...}, sub {...});

Sequentialize multiple events, every time the active 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 active event counter. This chain will continue until there are no more callbacks, a callback does not increment the active event counter or an error occurs 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://mojolicio.us.

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