--- darrik <darrik@xxxxxxxxxxxxxxxxxxx> wrote:
> Ashley Winters wrote:
> > use strict;
> > use Qt; # use Qt in EVERY package! It declares 'this', and does
> > other use-strict-happy things
> > use MyView;
> > sub processFileMenu {
> > if ($option==FILENEW) {
> > MyView(this)->show;
> > }
> > }
>
> You're not storing a perl reference to the new window anywhere. What
>
> happens when you want to access that window from the parent later?
Ahh, in that case you want to store it as a member variable. If, for
example, we wanted to populate the Window menu with the list of windows
opened with File->New or something...
package YourClass;
use strict;
use Qt;
use Qt::isa qw(Qt::Widget);
use Qt::attributes qw(windows); # declare a member variable
use MyView;
sub NEW {
# standard preamble
windows = []; # initialize as an array
}
sub processFileMenu {
if ($option==FILENEW) {
my $viewer = MyView(this);
$viewer->show;
push @{ windows }, $viewer;
}
}
>
> This is more evident when you subclass a container widget that has
> child
> controls. For instance:
I'll make the edits inline...
>
> use strict;
>
> package MyWidget;
>
> use Qt;
> use Qt::isa qw( Qt::Widget );
use Qt::attributes qw( lbl );
>
> sub NEW {
> # irrelevant method arguments left out for brevity :P
>
> my $class=shift;
> my $parent=shift;
> shift->SUPER::NEW($parent);
> my $layout=Qt::HBoxLayout(this);
#> my $lbl=Qt::Label("label",this);
#> $layout->addWidget($lbl);
# instead
lbl = Qt::Label("label",this);
$layout->addWidget(lbl);
> }
>
> sub changeChildLabel {
> # how do you access $lbl here?
lbl->setText("Qt::attributes");
> }
> This part has me confused. Storing $lbl in a package variable
> doesn't
> work if you instantiate several MyWidget's. I've been using
> workarounds
> that are inelegant, so a pointer to the *proper* way to do this would
> be
> immensely appreciated.
Sure. Keep in mind that the 'this' function/variable/keyword thing is,
in fact, a hash. You're free to store things in it, like so:
this->{'lbl'} = Qt::Label(...);
In fact, that's all the Qt::attributes pragma does, is setup that
shortcut. It automatically creates a lbl() function which returns
this->{'lbl'}, in a way that lets you assign to it (as an lvalue).
That's the technical side, at least. For more of a tutorial, read this:
http://perlqt.sourceforge.net/dist/current/doc/en/index.html#using_attributes
- Ashley Winters
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