[Pangloss] [RFC] OpenFrame AppKit ideas

[Jean-Michel Hiver]

>     +	make SessionLoader segment abstract, then subclass for
> 	Cookies, URL's, and Form params.

URLs? How are you going to get the URLs to be automagically appended
with some kind of sessionIDs?

Plus, I think a session model based on the user name (when you do
authentication via HTTP authentication) would also be a good idea.


> I'm forced to invent a way of handling errors.  I suppose I could
> just stick them in the Session and let the template writer deal
> with it.  But then I gotta remove them on each request, and what
> if I want to handle them before they get to the template?

Actually I found a neat little trick for error handling.


You define an error class:

  package My::Error;

  $THROW_CODEREF = sub { die shift() };
  
  # instanciates My::Object and invokes $THROW_CODEREF->($self) 
  sub new ($class);

  # for the error to be easily embeddable
  sub as_xhtml ($self);


Then you define an ErrorCatcher class:

  package My::ErrorCatcher;

  # adds an error to $error
  sub _add_error ($error);

  # returns a list of all errors
  # or an array ref in scalar context
  sub errors();

  sub has_errors();
  

Then in your code you do something like:

  use base qw /My::ErrorCatcher/;
  sub do_something
  {
      my $self = shift;
    
      # the current object is an ErrorCatcher, and at this point
      # we don't want the errors to be fatal.
      local $My::Error::THROW_CODEREF = sub {
          my $error = shift;
          $self->add_error ($error);
      };

      # the rest of the code goes here. If anything bad happened,
      # $self->has_errors() should return TRUE and we just need to
      # re-display the form and simply loop through the error array.
  }


If you use Petal, you then can display all the errors quite simply as
follows:

  <ul petal:condition="self/has_errors">
    <li petal:repeat="error self/errors"
        petal:content="structure error/as_xhtml">
      An Evil Error has occurred!
    </li>
  </ul>


Then you just need to make as many subclasses as you have different
errors, since you can actually define more than one package in a module
it's not too bad.

Cheers,
-- 
Building a better web - http://www.mkdoc.com/
---------------------------------------------
Jean-Michel Hiver
jhiver at mkdoc.com  - +44 (0)114 255 8097
Homepage: http://www.webmatrix.net/