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Reflex-0.071
River stage one • 7 direct dependents • 7 total dependents
13 ++
/ Reflex::Callbacks

NAME

Reflex::Callbacks - Convenience functions for creating and using callbacks

VERSION

version 0.071

SYNOPSIS

This package contains several helper functions, each with its own use case. Please see individual examples.

DESCRIPTION

Reflex::Callback and its subclasses implement the different types of calbacks that Reflex supports. Reflex::Callbacks provides convenience functions that are almost always used instead of Reflex::Callback objects.

Reflex::Callback's generic interface is a constructor and a single method, deliver(), which routes its parameters to their destination. Subclasses may implement additional methods to support specific use cases.

cb_method

Creates and returns Reflex::Callback::Method object. Accepts two positional parameters: the object reference and method name to invoke when the callback is delivered.

Relex::Callback::Method's SYNOPSIS has an example, as does the eg directory in Reflex's distribution.

cb_object

cb_object() converts the specification of multiple callbacks into a list of callback parameter names and their Reflex::Callback::Method objects. The returned list is in a form suitable for a Reflex::Base constructor.

cb_object() takes two positional parameters. The first is the object reference that will handle callbacks. The second describes the events and methods that will handle them. It may be a scalar string, an array reference, or a hash reference.

If the second parameter is a scalar string, then a single method will handle a single event. The event and method names will be identical. cb_object() will then return two values: the event name, and the Reflex::Callback::Method to invoke the corresponding object method.

        use Reflex::Callbacks qw(cb_object);
        my $object = bless {};
        my @cbs = cb_object($object, "event");

  # ... is equivalent to:

        use Reflex::Callback::Method;
        my $object = bless {};
        my @cbs = (
                on_event => Reflex::Callback::Method->new(
                        object => $object, method_name => "event"
                )
        );

If the second parameter is an array reference of event names, then one Reflex::Callback::Method will be created for each event. The event names and method names will be identical.

        use Reflex::Callbacks qw(cb_object);
        my $object = bless {};
        my @cbs = cb_object($object, ["event_one", "event_two"]);

        # ... is equivalent to:

        use Reflex::Callback::Method;
        my $object = bless {};
        my @cbs = (
                on_event_one => Reflex::Callback::Method->new(
                        object => $object, method_name => "event_one"
                ),
                on_event_two => Reflex::Callback::Method->new(
                        object => $object, method_name => "event_two"
                ),
        );

If the second parameter is a hash reference, then it should be keyed on event name. The corresponding values should be method names. This syntax allows event and method names to differ.

        use Reflex::Callbacks qw(cb_object);
        my $object = bless {};
        my @cbs = cb_object($object, { event_one => "method_one" });

        # ... is equivalent to:

        use Reflex::Callback::Method;
        my $object = bless {};
        my @cbs = (
                on_event_one => Reflex::Callback::Method->new(
                        object => $object, method_name => "method_one"
                )
        );

cb_class

cb_class() is an alias for cb_object(). Perl object and class methods currently behave the same, so there is no need for additional code at this time.

cb_role

cb_role() implements Reflex's role-based callbacks. These callbacks rely on method names to contain clues about the objects and events being handled. For instance, a method named on_resolver_answer() hints that it handles the "answer" events from a sub-object with the role of "resolver".

cb_role() requires two parameters and has a third optional one. The first two parameters are the callback object reference and the role of the object for which it handles events. The third optional parameter overrides the "on" prefix with a different one.

        {
                package Handler;
                sub on_resolver_answer { ... }
                sub on_resolver_failure { ... }
        }

        # This role-based definition:

        use Reflex::Callbacks qw(cb_role);
        my $object = Handler->new();
        my @cbs = cb_role($object, "resolver");

        # ... is equivalent to:

        use Reflex::Callbacks qw(cb_object);
        my $object = Handler->new();
        my @cbs = cb_object(
                $object, {
                        answer  => "on_resolver_answer",
                        failure => "on_resolver_failure",
                }
        );

        # ... or:

        use Reflex::Callbacks qw(cb_method);
        my $object = Handler->new();
        my @cbs = (
                on_answer => Reflex::Callback::Method->new(
                        object => $object, method_name => "on_resolver_answer"
                ),
                on_failure => Reflex::Callback::Method->new(
                        object => $object, method_name => "on_resolver_failure"
                ),
        );

cb_promise

cb_promise() takes a scalar reference. This reference will be populated with a Reflex::Callback::Promise object.

cb_promise() returns two values that are suitable to insert onto a Reflex::Base's constructor. The first value is a special event name, "on_promise", that tells Reflex::Base objects they may be used inline as promises. The second return value is the same Reflex::Callback::Promise object that was inserted into cb_promise()'s parameter.

        use Reflex::Callbacks qw(cb_promise);
        my $promise;
        my @cbs = cb_promise(\$promise);

        # ... is eqivalent to:

        use Reflex::Callback::Promise;
        my $promise = Reflex::Callback::Promise->new();
        @cbs = ( on_promise => $promise );

cb_coderef

cb_coderef() takes a single parameter, a coderef to callback. It returns a single value: a Reflex::Callback::Coderef object that will deliver events to the callback.

cb_coderef() neither takes nor returns an event name. As such, the Reflex::Base parameter name must be supplied outside cb_coderef().

        my $timer = Reflex::Interval->new(
                interval    => 1,
                auto_repeat => 1,
                on_tick     => cb_coderef { print "tick!\n" },
        );

As shown above, cb_coderef() is prototyped to make the callback's sub declaration optional.

Usages Outside Reflex

Reflex callbacks are designed to be independent of any form of concurrency. Reflex::Callbacks provides two convenience functions that other class libraries may find useful but Reflex doesn't use.

Please contact the authors if there's interest in using these functions, otherwise they may be deprecated.

gather_cb

The gather_cb() function extracts callbacks from an object's constructor parameters and encapsulates them in a Reflex::Callbacks object.

gather_cb() takes two parameters: A hash reference containing a constructor's named parameters, and an optional regular expression to match callback parameter names. By default, gather_cb() will collect parameters matching /^on_/.

        package ThingWithCallbacks;
        use Moose;

        use Reflex::Callbacks qw(gather_cb);

        has cb => ( is => 'rw', isa => 'Reflex::Callbacks' );

        sub BUILD {
                my ($self, $arg) = @_;
                $self->cb(gather_cb($arg));
        }

        sub run {
                my $self = shift;
                $self->cb()->deliver( event => {} );
        }

deliver

deliver() is a method of Reflex::Callback, not a function. It takes two parameters: the name of an event to deliver, and a hash reference containing named values to include with the event.

deliver() finds the callback that corresponds to its event. It then delivers the event to that callback. The callback must have been collected by gather_cb().

See the example for gather_cb(), which also invokes deliver().

SEE ALSO

Reflex Reflex::Callback::CodeRef Reflex::Callback::Method Reflex::Callback::Promise Reflex::Callbacks documents callback convenience functions.

"ACKNOWLEDGEMENTS" in Reflex "ASSISTANCE" in Reflex "AUTHORS" in Reflex "BUGS" in Reflex "BUGS" in Reflex "CONTRIBUTORS" in Reflex "COPYRIGHT" in Reflex "LICENSE" in Reflex "TODO" in Reflex