RE: MVC advice..?
Is there a neat way of dynamically loading in the appropriate control subclass? Something proven and widely used. For what it's worth, I use the eval trick too. Although it may seem a little clunky, I believe it is proven and widely used. The DBI.pm module uses code like this to load in the DBD drivers: my $driver_class = DBD::$driver; eval package DBI::_firesafe; require $driver_class; I'm not sure this answers your MVC questions, but maybe it will make you feel more comfortable with your solution. hth, aaron
Re: MVC advice..?
On Wed, 29 May 2002 09:22:00 -0400
Aaron Ross [EMAIL PROTECTED] wrote:
: Is there a neat way of dynamically loading in the appropriate control
: subclass? Something proven and widely used.
:
: For what it's worth, I use the eval trick too. Although it may seem a
: little clunky, I believe it is proven and widely used. The DBI.pm
: module uses code like this to load in the DBD drivers:
:
: my $driver_class = DBD::$driver;
: eval package DBI::_firesafe; require $driver_class;
I wonder, why do you program such a central module that dynamic? Why
do you chose that approach instead of this one?
package Dispatcher;
use Controller1;
# ...
use ControllerN;
sub handler {
my $r = Apache::Request-new(shift);
my $ctl = $r-param('ctl');
return Controller1::handler($r) if $ctl = 'login';
# ...
return ControllerN::handler($r) if $ctl = 'show_cart';
return SERVER_ERROR;
}
-- fxn
Re: MVC advice..?
Rafiq Ismail (ADMIN) wrote: Now my problem is that I have to assign which Subclass I want to instantiate, based on the script and params. So, you're asking how to map URLs to perl modules? Is there some reason you aren't simply using httpd.conf or Apache::Dispatch? In my last MVC design, we had all of our controllers inherit from one base controller that held all of the common code. Then we could just map from URLs to the specific controllers that handled them: Location /mycontroller SetHandler perl-script PerlHandler My::Controller /Location I my last effort I went for a Shared datastructure holding (script, control module pairs) which then allowed one to be dynamically eval 'use..''ed in the main content handler. I found that clunky. There's no good reason to do an eval 'use'. Use require instead, and import if you need to (but most people don't). I'm building from scratch again and am thinking of just firing up a template and allowing the control to be loaded INTO the view as a template toolkit plugin. What I hate about this is that I'm surrendering my View layer. I agree, that's a bad idea and certainly not MVC. - Perrin
Re: MVC advice..?
Ello, On 29 May 2002, Randal L. Schwartz wrote: Rafiq == Rafiq Ismail (ADMIN) [EMAIL PROTECTED] writes: Rafiq Is there a neat way of dynamically loading in the appropriate control Rafiq subclass? Something proven and widely used. Load the file with a require, and then just call the appropriate constructor using an indirect call: require My/Prefix/$type; # presuming $type has no colons $myClass = My::Prefix::$type; my $handler = $myClass-new(@parms); This works even in use strict. Thanks. This is pretty much the handler which I'd previously written, with the the exception of s/use/require/. I'll probably either go with Apache::Dispatch, using the DispatchRequire option, or write something custom. On Wed, 29 May 2002, Perrin Harkins wrote: So, you're asking how to map URLs to perl modules? Is there some reason you aren't simply using httpd.conf or Apache::Dispatch? In my last MVC I just took a look at Apache::Dispatch and I get he impression that if I were to use it then I would have to either PerlModule 'all' my subclasses beforehand, or alternateively use the DispatchRequire option anyway. I'm already using StatINC so I'm going to have to do a toss between code which I've already written and converging to the Apache::Dispatch interface. I'm not so keen on loading all the inheriting classes into memory beforehand, nor setting up multiple handlers for each location. It's a fairly large site and my main concern was to do with how I should store the correspondence from uri to object. design, we had all of our controllers inherit from one base controller that held all of the common code. I could just map from URLs to the specific control subclasses and then use Dispatch to require them - I'd already started on writing a mapping from path names to relative namespaces. I was still 'eval/use'ing the Modules though. How does StatINC behave with 'required' packages? Hmm.. it's make your mind up time. ;) Thanks for the tips. Cheers, Fiq __ __ __ _ __ __ | \/ | ___ __| | ___ _ __ _ __ | \/ | __ _ _ __ | |\/| |/ _ \ / _` |/ _ \ '__| '_ \| |\/| |/ _` | '_ \ | | | | (_) | (_| | __/ | | | | | | | | (_| | | | | |_| |_|\___/ \__,_|\___|_| |_| |_|_| |_|\__,_|_| |_| a pathetic example of his organic heritage - Bad Religion
Re: MVC advice..?
Dave Rolsky wrote: On Wed, 29 May 2002, Perrin Harkins wrote: There's no good reason to do an eval 'use'. Use require instead, and import if you need to (but most people don't). Actually, there is. This code: my $module = 'Foo::Bar'; require $module; is not the same as this: require Foo::Bar; If require is given a string, it looks for a filename _matching_ that string. If it's given a bareword, it converts '::' to filesystem path separators first. Then do an eval 'require Foo::Bar', but eval 'use Foo::Bar' doesn't make sense. - Perrin
Re: MVC advice..?
Rafiq Ismail (ADMIN) wrote: I'm not so keen on loading all the inheriting classes into memory beforehand You really should do that, because it will save overall memory by increasing the amount of memory that's shared. All modules should be loaded during startup in the parent process. It's a fairly large site and my main concern was to do with how I should store the correspondence from uri to object. The httpd.conf format seems about as simple as you can get to me. It's pretty unusual for a site to have dozens of controllers, and it usually indicates a design problem. Apache::Dispatch is fine too. How does StatINC behave with 'required' packages? Require and use are very similar and both add the loaded module to %INC. Read 'perldoc -f use' for the exact differences. - Perrin
Re: MVC advice..?
On Wed, 29 May 2002, Perrin Harkins wrote: There's no good reason to do an eval 'use'. Use require instead, and import if you need to (but most people don't). Actually, there is. This code: my $module = 'Foo::Bar'; require $module; is not the same as this: require Foo::Bar; If require is given a string, it looks for a filename _matching_ that string. If it's given a bareword, it converts '::' to filesystem path separators first. -dave /*== www.urth.org we await the New Sun ==*/
