[Wellington-pm] A question about scopes

[Andrew Boag]

So does this mean Cliff is up for throwing together an "Authoring Perl
Packages" talk ??? That would be a great topic for a future meeting.

On Tue, 2006-03-21 at 22:48 +1200, Grant McLean wrote:
> On Tue, 2006-03-21 at 21:39 +1200, Cliff Pratt wrote:
> > Erm, anyway, say the main script is like this:
> > 
> > use MyGame ;
> > .
> > my @grid ;
> > .
> > .
> > # Recent change - I now pass the grid to the packaged sub and
> > # return it when modified.
> > @grid = MyGame::sub1(@grid) ;
> 
> To save all the copying back and forth, you could pass a reference to
> @grid which would allow the module to modify the array back in the
> script:
> 
>   MyGame::sub1(\@grid);
> 
> Then you could learn Gtk2, packages *AND* references.
> 
> > .
> > .
> > 
> > The package is like this:
> > .
> > package MyGame;
> > 
> > # Recent change - This now outside any sub.
> > my @grid ;
> > 
> > sub sub1 {
> > 	# @grid, but which one?
> > 	@grid = @_ ;
> 
> You could grab the reference like this:
> 
>           ($grid) = @_;
> 
> And then refer to an element in the referenced array:
> 
>           print $grid->[0];
> 
> Or loop over all the elements:
> 
>           foreach my $item (@$grid) {
> 
> > 	.
> > 	return @grid ;
> > }
> 
> But it does sound like your module would benefit from being turned into
> an object.  That way you wouldn't need the global for @grid - you'd
> store the reference in the object where it would be available to all
> methods.  And if you instantiated two objects, they'd each have their
> own grid.
> 
> As you know from my Glade article, I like to arrange for Gtk GUI events
> to call methods on my object(s).  That way all the necessary state
> information is available in the object without having to use globals.
> 
> That would have the added advantage that you could learn Gtk2, packages
> *AND* references *AND* objects *AND* closures :-)
> 
> Cheers
> Grant
> 
> 
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