SYNOPSIS

# Define a mixin
package MyApp::FavoriteColor;
use base qw/ Jifty::DBI::Record::Plugin /;
# Define which methods you want to put in the host model
our @EXPORT = qw(
favorite_complementary_color
);
use Jifty::DBI::Schema;
use Jifty::DBI::Record schema {
column favorite_color =>
type is 'text',
label is 'Favorite Color',
valid_values are qw/ red green blue yellow /;
};
sub favorite_complementary_color {
my $self = shift; # whatever host object thing we've mixed with
my $color = $self->favorite_color;
return $color eq 'red' ? 'green'
: $color eq 'green' ? 'red'
: $color eq 'blue' ? 'orange'
: $color eq 'yellow' ? 'purple'
: undef;
}
# Use the mixin
package MyApp::Model::User;
use Jifty::DBI::Schema;
use Jifty::DBI::Record schema {
column name =>
type is 'text',
label is 'Name';
};
# Mixins
use MyApp::FavoriteColor;
sub name_and_color {
my $self = shift;
my $name = $self->name;
my $color = $self->favorite_color;
return "The favorite color of $name is $color.";
}
sub name_and_complementary_color {
my $self = shift;
my $name = $self->name;
my $color = $self->favorite_complementary_color;
return "The complement of $name's favorite color is $color.";
}

DESCRIPTION

By using this package you may provide models that are built from one or more mixins. In fact, your whole table could be defined in the mixins without a single column declared within the model class itself.

MODEL MIXINS

To build a mixin, just create a model that inherits from this package, "Jifty::DBI::Record::Plugin". Then, add the schema definitions you want inherited.

  package MyApp::FasterSwallow;
  use base qw/ Jifty::DBI::Record::Plugin /;
  
  use Jifty::DBI::Schema;
  use Jifty::DBI::Record schema {
      column swallow_type =>
          type is 'text',
          valid are qw/ african european /,
          default is 'african';
  };

@EXPORT

A mixin may define an @EXPORT variable, which works exactly as advertised in Exporter. That is, given the name of any methods or variable names in the mixin, the host model will gain those methods.

  our @EXPORT = qw( autocomplete_swallow_type );
  sub autocomplete_swallow_type {
      my $self  = shift;
      my $value = quotemeta(shift);
      # You should probably find a better way than actually doing this...
      my @values;
      push @values, 'african'  if 'african'  =~ /$value/;
      push @values, 'european' if 'european' =~ /$value/;
      return @values;
  }

That way if you have any custom methods you want to throw into the host model, just define them in the mixin and add them to the @EXPORT variable.

register_triggers

Your mixin may also want to register triggers for the records to which it will be added. You can do this by defining a method named "register_triggers":

  sub register_triggers {
      my $self = shift;
      $self->add_trigger( 
          name      => 'before_create', 
          callback  => \&before_create,
          abortable => 1,
      );
  }
  sub before_create {
      # do something...
  }

See Class::Trigger.

register_triggers_for_column

In addition to the general ``register_triggers'' method described above, the mixin may also implement a "register_triggers_for_column" method. This is called for each column in the table. This is primarily helpful for registering the "after_set_*" and "before_set_*" columns.

For example:

  sub register_triggers_for_column {
      my $self   = shift;
      my $column = shift;
      return unless $column ne 'updated_on';
      $self->add_trigger( 
          name      => 'after_set_'.$column, 
          callback  => \&touch_update_time,
          abortable => 1,
      );
  }
  sub touch_update_time {
      my $self = shift;
      $self->set_updated_on(DateTime->now);
  }

This has the additional advantage of being callable when new columns are added to a table while the application is running. This can happen when using database-backed models in Jifty (which, as of this writing, has not been released or made part of the development trunk of Jifty, but is part of the virtual-models branch).

See Class::Trigger.

MODELS USING MIXINS

To use your model plugin, just use the mixins you want to get columns from. You should still include a schema definition, even if it's empty:

  package MyApp::Model::User;
  use Jifty::DBI::Schema;
  use MyApp::Record schema {
  };
  # Mixins
  use MyApp::FavoriteColor;
  use MyApp::FasterSwallow;
  use Jifty::Plugin::User::Mixin::Model::User;
  use Jifty::Plugin::Authentication::Password::Mixin::Model::User;

LICENSE

Jifty::DBI is Copyright 2005-2007 Best Practical Solutions, LLC. Jifty is distributed under the same terms as Perl itself.