Re: Re: CRSC

[Corion]

I like this idea, but it has the major drawback that a hash dosen't preserve order, and in this case the order of application of those REs is important.

I don't know of any elegant solution to this (I'm using mostly the same method when creating multi-page CGI scripts), so the thing I'm using is a hash of page handlers and an array as the sequence of pages (yes, it's the dreaded wizard-style interface). Pages (== hash keys) that are not found in the sequence array are then either flagged as an error (more stability) or silently appended to the end of the wizard (quick'n'dirty development).

A sample :

my @pageorder = ( "welcome", "address", "recipients", "preview", "done
+" );

# Routines to create the pages
my %pages = (
  "welcome" => \&page_welcome,
  "address" => \&page_address,
  "recipients" => \&page_recipients,
  "preview" => \&page_preview,
  "done" => \&page_done,
);

# Routines to validate user input for every page
my %validators = (
  "welcome" => undef,
  "address" => \&validate_address,
  "recipients" => \&validate_recipients,
  "preview" => undef,
  "done" => undef,
);

And the page handler works like this :

# First, determine where we are, using a default of "welcome" on error
+ :
my $page;
if ($cgi->param("go_prev") and $cgi->param("prevpage")) {
  $page = $cgi->param("prevpage");
} else {
  $page = $cgi->param("nextpage");
};
if (! exists $pages{$page}) {
  $page = "welcome";
};

# Parameter validation ommitted, as it's simply a walk of the validati
+on chain for every page ...

# Execute the special code for this page, so all this searching had so
+me sense :
&{$pages{$page}};

[tye]

You could always use Tie::IxHash for this. You can also cheat and do what I find myself doing sometimes:

my @pages = (
  welcome => \&page_welcome,
  address => \&page_address,
  recipients => \&page_recipients,
  preview => \&page_preview,
  done => \&page_done,
);
my %pages= @pages;
@pages= do { my $key= 0; grep { $key= !$key } @pages };

Since you have two hashes with shared keys, you might go a different route like:

my( @pageorder, %pages, %validators );
for(
    ["welcome", \&page_welcome, undef],
    ["address", \&page_address, \&validate_address],
    ["recipients", \&page_recipients, \&validate_recipients],
    ["preview", \&page_preview, undef],
    ["done", \&page_done, undef],
) {
    push @pageorder, $_->[0];
    $pages{$_->[0]}= $_->[1];
    $validators{$_->[0]}= $_->[2];
}

or perhaps:

use mapcar;
my( @pageorder, %pages, %validators );
BEGIN {
    my( $key, $page, $valid )= mapcar {[@_]}
      ["welcome", \&page_welcome, undef],
      ["address", \&page_address, \&validate_address],
      ["recipients", \&page_recipients, \&validate_recipients],
      ["preview", \&page_preview, undef],
      ["done", \&page_done, undef];
    @pageorder= @$keys;
    @pages{@$keys}= @$page;
    @validators{@$keys}= @$valid;
}

Season to taste.
        - tye (but my friends call me "Tye")