My new question is why must I use the sub keyword when adding the methods as callbacks?

How else is Perl to know that you mean to pass a function reference? Remember that curly braces in Perl 5 can mean any of three things: a hash reference, a block, or an anonymous function passed to a prototyped function.

In effect, the code I posted:

$app->add_move_handler ( sub { $ship->move( @_ ) } );
$app->add_show_handler ( sub { $ship->draw( @_ ) } );

[download]

... is a shorter version of this code, using anonymous functions instead:

sub move_ship
{
    $ship->draw( @_ );
}

sub draw_ship
{
    $ship->draw( @_ );
}

$app->add_move_handler( \&move_ship );
$app->add_show_handler( \&draw_ship );

[download]

... or even:

my $move_ship = sub { $ship->move( @_ ) };
my $draw_ship = sub { $ship->draw( @_ ) };

$app->add_move_handler( $move_ship );
$app->add_show_handler( $draw_ship );

[download]

Do you follow so far?

In reply to Re^3: SDLx handlers and Moose by chromatic
in thread SDLx handlers and Moose by Ransom

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