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John Siracusa

NAME

Rose::DB::Object::Std - Standardized object representation of a single row in a database table.

SYNOPSIS

  package Category;

  use base 'Rose::DB::Object::Std';

  __PACKAGE__->meta->setup
  (
    table => 'categories',

    columns =>
    [
      id          => { type => 'int', primary_key => 1 },
      name        => { type => 'varchar', length => 255 },
      description => { type => 'text' },
    ],

    unique_key => 'name',
  );

  ...

  package Product;

  use base 'Rose::DB::Object::Std';

  __PACKAGE__->meta->setup
  (
    table => 'products',

    columns =>
    [
      id          => { type => 'int', primary_key => 1 },
      name        => { type => 'varchar', length => 255 },
      description => { type => 'text' },
      category_id => { type => 'int' },

      status => 
      {
        type      => 'varchar', 
        check_in  => [ 'active', 'inactive' ],
        default   => 'inactive',
      },

      start_date  => { type => 'datetime' },
      end_date    => { type => 'datetime' },

      date_created     => { type => 'timestamp', default => 'now' },  
      last_modified    => { type => 'timestamp', default => 'now' },
    ],

    unique_key => 'name',

    foreign_keys =>
    [
      category =>
      {
        class       => 'Category',
        key_columns => { category_id => 'id' },
      },
    ],
  );

  ...

  $product = Product->new(name        => 'GameCube',
                          status      => 'active',
                          start_date  => '11/5/2001',
                          end_date    => '12/1/2007',
                          category_id => 5);

  $product->save or die $product->error;

  $id = $product->id; # auto-generated on save

  ...

  $product = Product->new(id => $id);
  $product->load or die $product->error;

  print $product->category->name;

  $product->end_date->add(days => 45);

  $product->save or die $product->error;

  ...

DESCRIPTION

Rose::DB::Object::Std is a subclass of Rose::DB::Object that imposes a few more constraints on the tables it fronts. In addition to the constraints described in the Rose::DB::Object documentation, tables fronted by Rose::DB::Object::Std objects must also fulfill the following requirements:

  • The table must have a single primary key column named "id"

  • The value of the "id" column must be auto-generated if absent.

Different databases provide for auto-generated column values in different ways. Some provide a native "auto-increment" or "serial" data type, others use sequences behind the scenes.

Rose::DB::Object::Std (in cooperation with Rose::DB and Rose::DB::Object::Std::Metadata) attempts to hide these details from you. All you have to do is omit the value for the primary key entirely. After the object is save()ed, you can retrieve the auto-selected primary key by calling the id() method.

You do have to correctly define the "id" column in the database, however. Here are examples of primary key column definitions that provide auto-generated values, one for each of the databases supported by Rose::DB.

  • PostgreSQL

        CREATE TABLE mytable
        (
          id   SERIAL NOT NULL PRIMARY KEY,
          ...
        );
  • MySQL

        CREATE TABLE mytable
        (
          id   INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
          ...
        );
  • Informix

        CREATE TABLE mytable
        (
          id   SERIAL NOT NULL PRIMARY KEY,
          ...
        );

Other data definitions are possible, of course, but the three definitions above are used in the Rose::DB::Object::Std test suite and are therefore guaranteed to work. If you have success with alternative approaches, patches and/or new tests are welcome.

To achieve much of this functionality, Rose::DB::Object::Std uses Rose::DB::Object::Std::Metadata objects. The meta() method will create these form you. You should not need to do anything special if you use the idiomatic approach to defining metadata as shown in the synopsis.

METHODS

Only the methods that are overridden are documented here. See the Rose::DB::Object documentation for the rest.

meta

Returns the Rose::DB::Object::Std::Metadata object associated with this class. This object describes the database table whose rows are fronted by this class: the name of the table, its columns, unique keys, foreign keys, etc. See the Rose::DB::Object::Std::Metadata documentation for more information.

This can be used as both a class method and an object method.

AUTHOR

John C. Siracusa (siracusa@gmail.com)

LICENSE

Copyright (c) 2010 by John C. Siracusa. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.




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