[CDBI] Different subclasses for one table / Factory Pattern?
stephan.brunner at gmx.de
Thu Aug 3 21:31:46 BST 2006
Am Donnerstag 03 August 2006 18:43 schrieb Perrin Harkins:
> On Sun, 2006-07-30 at 21:19 +0200, Stephan Brunner wrote:
> > Right now, I have only one table for *all* files, but need to create
> > different File::<something> objects depending on column values (the file
> > name, for example). I want $dir->files() to return a list of objects in
> > the per-file-specific subclass. Is it possible to set this up using
> > Class::DBI?
> You can look at Class::DBI::Relationship::ISA or you can try making
> something yourself. When I needed to do something like this, I made a
> class that just had the primary key and the class name for columns and
> provided a method which would fetch the correct class of object. That
> does mean extra database fetches.
Perrin, thank you for the hint on ...::ISA. I looked at it, but, well, its
docs read a bit like "better don't use this module";-)
Right now, I'm thinking about giving up my subclasses in favour of a method
File->type() that tells me what kind of file I'm dealing with. I dislike the
idea because I'll have methods in package File that are invalid for certain
objects (for objects of wrong ->type()). But I like it because I can handle
all this in my own code and get full control without digging into any
inheritance internals. There are no additional database queries, and in the
application itself, I don't really mind whether to use
$file->isa('File::Foo') or $obj->type to decide what to do with a specific
Do I overlook something essential with this approach?
> - Perrin
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