[cgiapp] params, params, params...

[Joshua Miller]

On Feb 13, 2008 6:29 PM, Mark Knoop <mark at rawcane.net> wrote:

> >
> > Having said that, I can understand you might want a variable whose value
> > happens to come from one of several sources. I think such logic would
> > fit in your super class, and be stored in CGI::App's param() cache,
> > rather than inventing another (4th) location for such a cache. That 4
> > alone tells you it's overkill.
> >
>
> Is it bad policy to add properties to the CGI::App itself?
>
> eg saying
>
> $self->{my_special_value} = 'SOME_VALUE';


Yes, that's bad. You can technically do it, but you should tread lightly,
and be aware of the possible consequences. CGI::App is currently based on a
blessed hash, but that might not always be the case (though it's likely to
stay that way). It could move to an inside-out object, or array based, etc.
Also, it uses that to store stuff itself. When you call param, it sets those
in $self->{__PARAMS} hash. If your my_special_value was "__PARAMS", you'd
overwrite the internal __PARAMS hash, and break CGI::App.

As an example, the CGI::App perldoc PLUG-INS section...
       Writing Plug-ins

       Writing plug-ins is simple. Simply create a new package, and export
the methods that you
       want to become part of a CGI::Application project. See
CGI::Application::Plugin::Vali‐
       dateRM for an example.

       In order to avoid namespace conflicts within a CGI::Application
object, plugin developers
       are recommended to use a unique prefix, such as the name of plugin
package, when storing
       information. For instance:

        $app->{__PARAM} = 'foo'; # BAD! Could conflict.
        $app->{'MyPlugin::Module::__PARAM'} = 'foo'; # Good.
        $app->{'MyPlugin::Module'}{__PARAM} = 'foo'; # Good.

So if you're going to do it, be careful.


>
>
> instead of
>
> $self->param(my_special_value, 'SOME_VALUE');

?
>
> I guess it is bad policy otherwise the params method would not exist but
> it
> would be useful to understand exactly why this is?
>
> Cheers
> Mark
>
>
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