inheritance

[Peter Scott]

At 06:17 PM 2/20/03 -0800, Darren Duncan wrote:
>On Wed, 19 Feb 2003, nkuipers wrote:
> > Child constructor is as follows:
> >
> > sub new {
> >       my $type = shift;
> >       my $self = {};
> >       $self->{bogus_key} = BIO::Basic->new(@_);
> >       bless $self, $type;
> > }
>
>Your child constructor is incorrect, and in this case, unnecessary.

Correct, unless he wants to do something in the constructor before 
releasing the object into the wild.  I should have said so before.

>The only reason to make your own new() is if you need to
>override or supplement functionality in the parent's new().  In the latter
>case, your child class' new() should look like this:
>
>sub new {
>         my $self = SUPER::new(@_);  # puts blessed hash in $self

Hmm, and here all the time I've been doing

         my $class = shift;
         my $self = $class->SUPER::new(@_);

Are you sure that with your approach it will go up the inheritance tree 
if it doesn't find new() in the first superclass?  I thought you needed 
a -> method call for that.

>         # put other special functionality here
>         return($self);
>}
>
>Note that "SUPER" is a special Perl keyword that refers to the parent
>class.  That said (and I don't really like this), when you have multiple
>inheritence, SUPER won't work

Well, it might :-)  All depends which class it finds first.

>and you have to say instead
>"Bio::Basic::new(@_)".

Assuming that's the parent you want to inherit the constructor.  If you 
want some hybrid of the multiple parents' constructors you have to 
figure it out the hard way, right?
--
Peter Scott
Pacific Systems Design Technologies
http://www.perldebugged.com/