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.\" ========================================================================
.\"
.IX Title "AnyEvent::Callback 3pm"
.TH AnyEvent::Callback 3pm "2012-06-30" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
AnyEvent::Callback \- callback aggregator for AnyEvent watchers.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    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
.Ve
.PP
Callback hierarchy
.PP
.Vb 1
\&    my $cbchild = $cb\->CB(sub { ... });
\&
\&    ...
\&
\&    $cbchild\->error(\*(Aqerror\*(Aq); # will call $cb\->error(\*(Aqerror\*(Aq);
.Ve
.PP
Inside Your callback You can:
.PP
.Vb 3
\&    sub my_watcher {
\&        my $cb = pop;
\&        my @args = @_;
\&
\&        # ...
\&
\&        $cb\->error( @error );   # error callback will be called
\&        # or:
\&        $cb\->( $value );        # result callback will be called
\&    }
.Ve
.PP
Callbacks stack
.PP
.Vb 1
\&    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;
\&            }
\&        }
\&
\&    });
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The module allows You to create callback's hierarchy. Also the module groups
error and result callbacks into one object.
.PP
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.
.PP
Also the module checks if a callback was called reentrant. In the case the
module will complain (using \*(L"carp\*(R" in Carp).
.PP
If a watcher touches error callback and if superior didn't define error
callback, the module will call error callback upwards hierarchy. Example:
.PP
.Vb 1
\&    AE::something @args, CB \e&my_watcher, \e&on_error;
\&
\&    sub on_error {
\&
\&    }
\&
\&    sub my_watcher {
\&        my $cb = pop;
\&
\&        ...
\&
\&        the_other_watcher $cb\->CB( sub { # error callback wasn\*(Aqt 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
\&
\&            });
\&        });
\&    }
.Ve
.SH "METHODS"
.IX Header "METHODS"
.SS "'\s-1CODE\s0' (overloaded fake method)"
.IX Subsection "'CODE' (overloaded fake method)"
.Vb 1
\&    $cb\->( ... );
.Ve
.PP
You can use the object as usually \fB\s-1CODEREF\s0\fR.
.SS "\s-1CB\s0"
.IX Subsection "CB"
Creates new callback object that have binding on parent callback.
.PP
.Vb 1
\&    my $new_cb = $cb\->CB(sub { ... });   # the cb doesn\*(Aqt catch errors
\&
\&    my $new_cb = CB(sub { ... }, sub { ... }); # the cb catches errors
\&
\&    my $new_cb = $cb\->CB(sub { ... }, sub { ... }); # the same
.Ve
.SS "error"
.IX Subsection "error"
Calls error callback. If the object has no registered error callbacks,
parent object's error callback will be called.
.PP
.Vb 1
\&    $cb\->error(\*(AqWTF?\*(Aq);
.Ve
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
.Vb 1
\& Copyright (C) 2012 by Dmitry E. Oboukhov
.Ve
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.