Re: abstract class with Class::DBI

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As you are using Pg, you could use trhe table inheritance of the rdbms.
I don't know if CDBI works well with inherited tables, but it should be
possible to move all the magic into the rdbms, leading to much simpler code.

Edward Betts wrote:
| I've got a bunch of activities, they are of different types like e-mail,
| SMS, and registration. They are represented by an abstract class, called
| Activity, with subclasses for each type, called ActivityEmail,
ActivitySms,
| and ActivityReg. I'm trying to work out how to store them using
Class::DBI.
|
| I'm using PostgreSQL for the database, fields that are common to all the
| types are stored the activity table.
|
| create table activity (
|     id            serial primary key,
|     title         varchar(50),
|     activitytype  character(10) check (activitytype in ('email',
'sms', 'reg'));
|     activitydate  date,
| );
|
| create table activity_email (
|     activity   integer primary key references activity(id),
|     subject    varchar(80),
|     body       text,
|     whofrom    varchar(80),
|     whoto      varchar(80),
| );
|
| create table activity_sms (
|     activity   integer primary key references activity(id),
|     message    varchar(160)
| )
|
| create table activity_reg (
|     activity    integer primary key references activity(id),
|     purpose     varchar(15) check (purpose in ('General', 'Competition')),
| );
|
| For each activity there is one entry in the activity table, and one in the
| table for that specific type.
|
|
| Column definitions are provided by Class::DBI::Loader, here is the
| Class::DBI code to describe the classes:
|
| package MyApp::Activity;
|
| __PACKAGE__->might_have(activity_email => 'VV::ActivityEmail');
| __PACKAGE__->might_have(activity_sms => 'VV::ActivitySms');
| __PACKAGE__->might_have(activity_reg => 'VV::ActivityReg');
|
| package MyApp::ActivityEmail;
| use base qw(MyApp::Activity);
|
| __PACKAGE__->has_a(activity => 'MyApp::Activity');
|
| package MyApp::ActivitySms;
| use base qw(MyApp::Activity);
|
| __PACKAGE__->has_a(activity => 'MyApp::Activity');
|
| package MyApp::ActivityReg;
| use base qw(MyApp::Activity);
|
| __PACKAGE__->has_a(activity => 'MyApp::Activity');
|
|
| Does all of this look right, or should I be doing it another way?

- --
Grüße,

Andreas Fromm

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