SYNOPSIS

use AnyEvent::Callback;
# usually watchers are looked as:
AE::something @args, sub { ... };
AE::something
@args,
sub { ... }, # result
sub { ... }; # error
use AnyEvent::Callback;
AE::something @args, CB { ... };
AE::something @args,
CB sub { ... }, # result
sub { ... }; # error
AE::something @args,
CB sub { ... }, # result
sub { ... }, # error
sub { ... }; # anyway callback

Callback hierarchy

    my $cbchild = $cb->CB(sub { ... });
    ...
    $cbchild->error('error'); # will call $cb->error('error');

Inside Your callback You can:

    sub my_watcher {
        my $cb = pop;
        my @args = @_;
        # ...
        $cb->error( @error );   # error callback will be called
        # or:
        $cb->( $value );        # result callback will be called
    }

Callbacks stack

    my $cbs = CBS;
    for (1 .. $n) {
        AE::something @args, $cbs->cb;
    }
    $cbs->wait(sub {
        for (@_) {
            if ($_->is_error) {     # handle one error
                my @err = $_->errors; # or:
                my $errstr = $_->errstr;
            } else {                # results
                my @res = $_->results;
            }
        }
    });

DESCRIPTION

The module allows You to create callback's hierarchy. Also the module groups error and result callbacks into one object.

Also the module checks if one callback was called by watcher or not. If a watcher doesn't call result or error callback, error callback will be called automatically.

Also the module checks if a callback was called reentrant. In the case the module will complain (using ``carp'' in Carp).

If a watcher touches error callback and if superior didn't define error callback, the module will call error callback upwards hierarchy. Example:

    AE::something @args, CB \&my_watcher, \&on_error;
    sub on_error {
    }
    sub my_watcher {
        my $cb = pop;
        ...
        the_other_watcher $cb->CB( sub { # error callback wasn't defined
            my $cb = pop;
            ...
            yet_another_watcher1 $cb->CB( sub {
                my $cb = pop;
                ...
                $cb->( 123 );   # upwards callback
            });
            yet_another_watcher2 $cb->CB( sub {
                my $cb = pop;
                ...
                $cb->error( 456 );  # on_error will be called
            });
        });
    }

METHODS

'CODE' (overloaded fake method)

    $cb->( ... );

You can use the object as usually CODEREF.

CB

Creates new callback object that have binding on parent callback.

    my $new_cb = $cb->CB(sub { ... });   # the cb doesn't catch errors
    my $new_cb = CB(sub { ... }, sub { ... }); # the cb catches errors
    my $new_cb = $cb->CB(sub { ... }, sub { ... }); # the same

error

Calls error callback. If the object has no registered error callbacks, parent object's error callback will be called.

    $cb->error('WTF?');

COPYRIGHT AND LICENCE

 Copyright (C) 2012 by Dmitry E. Oboukhov

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