Class::AlzaboWrapper - Higher level wrapper around Alzabo Row and Table objects

  package WebTalk::User;
  use base 'Class::AlzaboWrapper';

  __PACKAGE->SetAlzaboTable( $schema->table('User') );
  __PACKAGE->MakeColumnMethods();

This module is intended for use as a base class when you are writing a class that wraps Alzabo's table and row classes.

It also provides a way to generate some methods specific to your subclass.

Our usage examples will assume that there is database containing tables named "User" and "UserComment", and that the subclass we are creating is called WebTalk::User.

This module throws exceptions when invalid parameters are given to methods. The exceptions it throws are objects which inherit from Exception::Class::Base, just as with Alzabo itself.

This method must be called by your subclass or almost none of the methods provided by Class::AlzaboWrapper will work.

Subclasses inherit a number of method from Class::AlzaboWrapper.

* new(...)

The new() method provided allows you to create new objects either from an Alzabo row object, or from the main table's primary keys.

This method first looks to see if the parameters it was given match the table's primary key. If they do, it attempts to create an object using those parameters. If no primary key values are given, then it looks for an parameter called "object", which should be an Alzabo::Runtime::Row object.

Finally, if your subclass defines a _new_row() method, then this will be called, with all the parameters provided to the new() method. This allows you to create new objects based on other parameters.

If your subclass defines an _init() method, then this will be called after the object is created, before it is returned from the new() method to the caller.

If invalid parameters are given then this method will throw a Class::AlzaboWrapper::Exception::Params exception.

* create(...)

This method is used to create a new object and insert it into the database. It simply calls the insert() method on the class's associated table object. Any parameters given to this method are passed given to the insert() method as its "values" parameter.

* potential(...)

This creates a new object based on a potential row, as opposed to one in the database. Similar to the create() method, any parameters passed are given to the table's potential_row() method as the "values" parameter.

* Columns(...)

This is simply a shortcut to the associated table's columns method. This may also be called as an object method.

* Column(...)

This is simply a shortcut to the associated table's column method. This may also be called as an object method.

* Table()

This method returns the Alzabo table object associated with the subclass. This may also be called as an object method.

* AlzaboAttributes()

Returns a list of accessor methods that were created based on the columns in the class's associated table.

* NewCursor ($cursor)

Given an Alzabo::Runtime::Cursor object (either a row or join cursor), this method returns a new Class::AlzaboWrapper::Cursor object.

* row_object()

This method returns the Alzabo::Runtime::Row object associated with the given subclass object. So, for our hypothetical WebTalk::User class, this would return an object representing the underlying row from the User table.

* select() / update() / delete() / is_live()

These methods are simply passthroughs to the underlying Alzabo row methods of the same names. You may want to subclass some of these in order to change their behavior.

If you call this method on your subclass, then for each column in the associated table, a method will be created in your subclass that selects that column's value from the underlying row for an object.

For example, if our User table contained "username" and "email" columns, then our WebTalk::User object would have username() and email() methods generated.

The MakeColumnMethods() method accepts a "skip" parameter which can be either a scalar or array reference. This is a list of columns for which methods should not be generated.

The Class::AlzaboWrapper module has a method it provides:

* TableToClass($table)

Given an Alzabo table object, this method returns its associated subclass.

When using this module, you need to use the Class::AlzaboWrapper::Cursor module to wrap Alzabo's cursor objects, so that objects the cursor returns are of the appropriate subclass, not plain Alzabo::Runtime::Row objects. The Cursor() method provides some syntactic sugar for creating Class::AlzaboWrapper::Cursor objects.

If you want to record the accessor methods your subclass makes so they are available via AlzaboAttributes(), you can call the _RecordAttributeCreation() method, which expects two arguments. The first argument is the class for which the method was created and the second is the name of the method.

The Alzabo docs are conveniently located online at http://www.alzabo.org/docs/.

There is also a mailing list. You can sign up at http://lists.sourceforge.net/lists/listinfo/alzabo-general.

Please don't email me directly. Use the list instead so others can see your questions.

VegGuide.Org is a site I created which actually uses this code as part of the application. Its source is available from the web site.

Copyright (c) 2002-2005 David Rolsky. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

Dave Rolsky, <autarch@urth.org>