Understanding and building modules

neilwatson has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to build a module but, I don't have clear understanding of how to go about this. Module (../site-perl/5.8.2/Mapps/Auth.pm):

package Mapps::Auth;
use Digest::SHA1;
use DBI;
use warnings;
use strict;

sub new {
    my $self = {}; 
    bless $self;
    return $self;  
}

sub auth {
    my ($uname, $passwd, $dbsecret, $salt); 
    $uname = shift;
    $passwd = shift;

    my $dbh = DBI->connect('dbi:mysql:mapps', 'mapps', 'somepasswd');
    # get secret from db
    my $statement="SELECT
    auname,
    passwd,
    salt
    FROM
    admin_users,
    secrets
    WHERE
    users.auid=secrets.auid
    AND
    auname='$uname';";

    my $sth = $dbh->prepare($statement) or die "Couldn't prepare state
+ment: $dbh->errstr";
    $sth->execute or die "Couldn't execute statement: $dbh->errstr";

    while (my $ref = $sth->fetchrow_hashref){
        $dbsecret = $ref->{'passwd'};
        $salt = $ref->{'salt'};
    }

    # encrypts password using
    # SHA-1 algorithm
    my $sha1 = Digest::SHA1->new;

    # reset algorithm
    $sha1->hexdigest;

    # encrypt
    my $secret = Digest::SHA1::sha1_hex($passwd . $salt);    

    # does generated secret match database secret?
    if ($secret eq $dbsecret){
        my $auth = 1;
        return $auth;

    # no match
    }else{
        my $auth = 0;
        return $auth;
    }
}
1;
[download]

Calling the module:

use Mapps::Auth;

$auth = new Mapps::Auth->auth($uname, $passwd);

if ($auth == 1){
    my $s = Mapps::Session->new();
    my $id = Apache::Session::Generate::MD5::generate();
    $s->new_session($id);
    my $sid = $s->sid();

    # show session from Jeremy's test script
    printf("SID %s\n", $s->sid());
    printf("UID %s\n", $s->uid());

    $s->param('foo','123 456');
    $s->param(bar =>' baz');
    $s->update_session($s->sid());

    undef($s);

    my $x = Mapps::Session->new();
    $x->load_session($sid);

    my @keys = $x->param();

    foreach my $key (@keys) {
        printf("%s => %s\n", $key, $x->param($key));
    }
# else no auth
}else{
    print h2('No authentication');
}
[download]

I'm getting the error: Can't locate object method "new" via package "Mapps::Auth"

Can some kind monk please explain the nature of creating modules and using them?

Neil Watson
watson-wilson.ca

edited: Sat Apr 3 21:53:56 2004 by jeffa - corrected title misspelling, added readmore

Comment on Understanding and building modules Select or Download Code

Replies are listed 'Best First'.
Re: Understanding and building modules by jeffa (Bishop) on Apr 03, 2004 at 20:22 UTC
Perl OO tutorial for beginners Perl OO tutorial, part 1 Perl OO tutorial, part 2 Perl OO tricks and examples Perl modules: how they work Perl modules: how to write and use Perl modules: how to write modules with style Perl modules: how to install from CPAN Perl modules: preparing a new module for distribution jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply]
Re: Understanding and building modules by BUU (Prior) on Apr 03, 2004 at 22:04 UTC
`$auth = new Mapps::Auth->auth($uname, $passwd);` Just guessing, but this code looks really, really wrong. I'm not sure exactly what it'll do (my best guess is it calls the method "new" on the return of auth->auth, but indirect function calls are funky). Try changing it to two lines and see if it fixes your problems: `$auth = Mapps::Auth->new(); $auth->auth($uname, $passwd);` [download] Or alternatively `Mapps::Auth->new()->auth($uname,$passwd);`	[reply] [d/l] [select]
2Re: Understanding and building modules by jeffa (Bishop) on Apr 03, 2004 at 22:24 UTC
And while we are at it, change: `sub auth { my ($uname, $passwd, $dbsecret, $salt); $uname = shift; $passwd = shift; ... }` [download] to `sub auth { my ($self, $uname, $passwd) = @_; my ($dbsecret, $salt); ... }` [download] or the method call will not work. Here is a little test script i came up with. Looks like the problem isn't in the constructor as i originally suspected, but instead in that wacky method call/instantiation. `ref new Foo or warn "example 1 is not an object\n"; ref new Foo->foo or warn "example 2 is not an object\n"; package Foo; sub new { bless {} } sub foo { "foo" }` [download] jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]
Re: Undertanding and building modules by gmpassos (Priest) on Apr 03, 2004 at 20:29 UTC
To use a module, first you need to load it. Soo, your code should be: `use Mapps::Auth ; $auth = new Mapps::Auth->auth($uname, $passwd); ...` [download] Note that your module need to be in some @INC path. To see what directories your Perl interpreter is lookin for modules, get the output of this code: `foreach my $INC_i ( @INC ) { print "$INC_i\n" ; }` [download] Here the output is: `C:/Perl/lib C:/Perl/site/lib .` [download] Graciliano M. P. "Creativity is the expression of the liberty".	[reply] [d/l] [select]
Re: Re: Undertanding and building modules by neilwatson (Priest) on Apr 03, 2004 at 21:24 UTC
Yes, I do have use Mapps::Auth; and it is loaded in a place where perl can find it. Neil Watson watson-wilson.ca	[reply]
Re: Re: Re: Undertanding and building modules by peanut (Novice) on Apr 03, 2004 at 22:27 UTC
Do you in fact have a directory "Mapps" containing a module "Auth.pm", because as far as i now this is where Perl will look for it (e.g. current directory). To me it really looks like Perl can not find the module at all. You also could include a use diagnostics; in your code or take everything away but the new method and try to load the module and just call new. I also always bless the self hash inside the new method, because otherwise you later may get an error like can't call method "auth" on unblessed reference	[reply]
Re: Understanding and building modules by tachyon (Chancellor) on Apr 04, 2004 at 06:34 UTC
Simple Module Tutorial cheers tachyon	[reply]
Re: Understanding and building modules by matija (Priest) on Apr 03, 2004 at 20:28 UTC
Your example doesn't say: Did you do a `use Mapps::Auth;` [download] in your code? Because that's the kind of message I get when I forget to do that.	[reply] [d/l]
Re: Understanding and building modules by TStanley (Canon) on Apr 04, 2004 at 05:22 UTC
If you want to read a couple of good books on the creation/maintenance of modules, I can suggest Learning Perl Objects, References and Modules which is written by merlyn and Writing Perl Modules for CPAN which is written by samtregar TStanley -------- The only thing necessary for the triumph of evil is for good men to do nothing -- Edmund Burke	[reply]