Re: many2many

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Hi Will--

    I see that the correct form for using the class::dbi::factory variable 
$rebase is not

$rebase->db_name

but is

$rebase->config->get('db_username')

which works fine. What prompted this in the first place was the code:

  my $enzyme_name = 'TstI';
  my $enzyme = $rebase->retrieve('enzyme', name => $enzyme_name);
  my @sites = $enzyme->sites;

which gives the error:

db_username: no such variable
db_password: no such variable
dbi_trace: no such variable
sth_to_objects needs a statement handle

When I am not using the factory, the code

Enzyme->retrieve(name => $enzyme_name);

works fine.

TIA,

Barry

----- Original Message ----- 
From: "Barry Dancis" <bdancis@xxxxxxx.xxx>
To: "William Ross" <will@xxxxxxx.xxx>
Cc: "class dbi list" <cdbi-talk@xxxxxx.xxxxx.xxx>
Sent: Tuesday, April 12, 2005 10:43 AM
Subject: Re: many2many


> Hi Will--
>
>    Thanks, I got the many2many to work and I agree with you about the 
> naming conventions. I was using tables designed by someone else.
>
>    Now that I've got that working, I am back to getting cdbi factory to 
> work, but I can't seem to  get it initialized correctly. The code has:
>
> use base 'Class::DBI::Factory';
> my $rebase = Class::DBI::Factory->new;
>   $rebase->set_db ({db_type => 'mysql',
>                 db_name => 'rebase:localhost',
>                 db_username => 'barry',
>                 db_password => '',
>                });
>   $rebase->use_classes (qw/Enzyme Site EnzymeSite/);
>   print "db_name: " . $rebase->db_name . "\n";
>
> but then I get the output:
>
> Use of uninitialized value in concatenation (.) or string at 
> C:\Development\Perl\try\Tisdall\try_many2many.pl line 26.
> db_name:
>
> Set_db did not initialize the values for db name,  username and  password 
> even thought I used the same values when I used class::bdi->set_db. I also 
> tried
>
> db_type => 'dbi:mysql',
>
> in the factory set_db but that didn't help either.
>
> TIA
>
> Barry
>
> ----- Original Message ----- 
> From: "William Ross" <will@xxxxxxx.xxx>
> To: "Barry Dancis" <bdancis@xxxxxxx.xxx>
> Cc: "class dbi list" <cdbi-talk@xxxxxx.xxxxx.xxx>
> Sent: Monday, April 11, 2005 2:58 PM
> Subject: Re: many2many
>
>
>
> On 11 Apr 2005, at 17:46, Barry Dancis wrote:
>
>> I am trying to implement a many to many relationship with
>>
>> #=============================
>> {package Sites;
>> Sites->has_many (siteenzymes => ['EnzymeSites' => 'enzid']);
>>
>> #=============================
>> {package Enzymes;
>> Enzymes->has_many (enzsites => ['EnzymeSites' => 'siteid']);
>>
>> #=============================
>> {package EnzymeSites;
>> EnzymeSites->columns(Primary => qw/ siteid enzid /);
>> EnzymeSites->has_a (enzid => 'Enzymes');
>> EnzymeSites->has_a (siteid => 'Sites');
>>
>> but when I execute:
>>
>> my $enzyme = Enzymes->retrieve(enzyme => 'TstI');
>> my @sites = $enzyme->enzsites;
>> I get the error:
>>
>> enzymes is not a column of EnzymeSites
>
> The foreign class column name in a has_many relationship defaults to
> the moniker of the calling class, on the reasonable assumption that
> when a cd has many tracks, the cd of the track will be recorded in a
> column called 'cd'. This is in the docs.
>
> If i remember rightly, the moniker of a class defaults to the name of
> its data table if no other moniker is declared. I don't think this is
> in the docs.
>
> Your Enzymes class is declaring a has_many relationship with
> EnzymeSites. The extra [] clause just tells that relationship object to
> return a column of the EnzymeSites object rather than returning the
> whole object.
>
> The data table for your Enzyme class is called 'enzymes'. By default
> the has_many relationship will get that as the moniker and look for a
> column with that name in the EnzymeSites class, but the real name of
> the column is 'enz_id'. To avoid this trouble, you just have to specify
> the column name. To avoid future trouble, I'd specify the class moniker
> too:
>
> Enzymes->moniker('enzyme');
> Enzymes->has_many(enzsites => ['EnzymeSites' => 'siteid'], 'enzid');
> Sites->has_many (siteenzymes => ['EnzymeSites' => 'enzid'], 'siteid');
>
> Personally I also avoid the 'id' suffix on column names: it describes
> the contents of the column well enough, but becomes confusing when the
> column is inflated. In your case, it leads to statements like:
>
> my $site_id = $enzyme->site_id->siteid;
>
> But that's very much a question of taste, and there are plenty here who
> would disagree.
>
> best
>
> Will
>
> ps. Tony, didn't the moniker used to de-pluralise itself? Or did I
> imagine that?
>
>