----- Original Message -----
From: "Rob Dixon" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, October 21, 2003 4:31 AM
Subject: Re: Beginning beginner needing references help
> Jonathan Mangin wrote:
> >
> > Jeez, this is a beginner's list?
> >
Thank you for all the responses. I'll try to answer everyone's concerns
here.
This is an inherited project I'm converting from cgi-lib.pl to cgi.pm. I'm
purposely doing everything the hard way in an effort to learn more core
perl.
Session management is next, then converting to C::A. That's the plan.?
> > #!/usr/bin/perl -wT
> > use strict;
> >
> > [CGI and DBI stuff]
> >
> > $countryid="1";
$countryid is being declared globally with use vars. It's processed and
stored where
needed but is meaningless at this time.
> > $statename=$gotcha;
> > @r_states=getStates([EMAIL PROTECTED], \%states1, \%states2);
> > $stateid=$states2{$statename};
> > @r_counties=getCounties([EMAIL PROTECTED], \%counties1);
> >
Best practices or less, I intended (at this time) these arrays/hashii to be
global. More later...
> > if ($CGI->param("Register")) {
> > Register($CGI, \%$counties1);
> > }
Hmm, I truly thought the syntax should be: Register($CGI, \%counties1);
I cut and pasted one of my fanciful iterations.
> > elsif ($CGI->param("Verify")) {
> > Verify($CGI);
> > }
> > else {
> > displayLoginScreen($CGI);
> > }
> > sub displayLoginScreen {
> > [misc stuff]
> >
Let's add to the following for a test:
> > foreach $state(@states) {
> > print "<option>$state";
> > }
foreach $county(@counties) {
print "<option>$county";
}
Now the list of states also includes the counties (fetched previously based
on $stateid).
> >
> > [more stuff]
> > }
> >
> > Through the scope(?) of displayLoginScreen (main?) all of the
> > state/county arrays/hashes are available, though note the
> > @states syntax instead of @$states. (Why is this syntax
> > working?) The states data is more persistent (I'll later
> > figure out why if ever a pattern emerges), but Verify knows
> > the county stuff only until the first validation error.
>
> All of the variables that you've declared ouside any subroutines
> are accessible throughout the rest of the file, both within and
> outside subroutines. You're simply accessing the common
> '@states' variable in 'displayLoginScreen'. '@states' and
> '$states' are totally unrealted: they just happen to have the
> same identifier. The syntax '@$states' is an attempt to
> dereference the value in the '$states' scalar as an array. This
> will fail unless '$states' holds an array reference. I don't
> understand what you mean by "more persistent" or by 'Verify'
> knows the county stuff only until the first validation error."
> You're passing no references to 'Verify' so it can only be
> accessing the common variables like '@states'.
>
Subroutine 'Verify' processes the fields from displayLoginScreen,
validates the input and checks the db for existing records. (We're
actually attempting a new registration here.) i.e.:
sub Verify {
my $cgi=shift;
$uid=$cgi->param(-name=>'uid');
if (length($uid) < 6) {
displayLoginScreen($cgi);
}
elsif (nextErrorCondition) {
displayLoginScreen($cgi);
} else {
[more stuff]
if ([more stuff] =OK) {
displayRegisterScreen($cgi);
}
}
}
Upon the first error condition being true (or true again) and subroutine
displayLoginScreen being [re]called, my list of select options still
includes
@states but not @counties. Are these not global, or is @counties being
undefined somehow?
> > Instead of making subsequent db fetches I want to send(?)
> > any/all of these to any/all subsequent (inner?) subroutines
> > that may need them. Is this possible and what might the
> > referencing/dereferencing look like?
>
> You can either do what you've done above, and simply declare
> common variables at a wider scope so that they're accessible
> everywhere or - more properly - pass references to all of the
> data as as parameters. You'd then have something like
>
> displayLoginScreen($CGI, [EMAIL PROTECTED]);
>
> sub displayLoginScreen {
> my ($CGI, $states) = @_;
> foreach my $state (@$states) {
> :
> }
> }
>
> > Verify calls other subroutines and then another HTML page.
> > That page calls Register. Do I need to send references to
> > Verify before sending them to the other subs?
>
> If you're expecting the call to the other subroutines to pass
> all of the data they need, then clearly the calling code has to
> have access to that data to be able to pass it on. This is where
> parameterising all data can get messy, and it becomes more
> appropriate to use common data accessible everywhere, preferably
> with some naming convention that makes it clear that it is
> global data.
>
If I need to explicitly pass data (references) to subroutines that's OK
cause that's what I'm trying to learn. The @states vs. @counties
inconsistency has me confused.
>
> but you seemed to know what to do in the previous call to
> 'getStates', like this.
>
> getStates([EMAIL PROTECTED], \%states1, \%states2)
>
> I hope that helps.
>
>Rob
Thanks, it helps a great deal. I have more fanciful code to try.
I've snagged an example from CGI Programming with Perl to
model after but I suspect my if-elsing above looks like I'm still
cgi-libbing.
--Jon
>
>
>
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