use Scalar::Util qw(blessed);
use namespace::autoclean;
+our $VERSION = 0.01;
+
+__PACKAGE__->mk_group_accessors(simple => qw(parent_source additional_parents));
+
# how this works:
#
# On construction, we hook $self->result_class->result_source_instance
#
# deploying the postgres rules through SQLT may be a pain though.
-__PACKAGE__->mk_group_accessors(simple => qw(parent_source additional_parents));
-
method new ($class: @args) {
my $new = $class->next::method(@args);
my $rc = $new->result_class;
return $new;
}
+method add_additional_parents (@classes) {
+ foreach my $class (@classes) {
+ Class::C3::Componentised->ensure_class_loaded($class);
+ $self->add_additional_parent(
+ $class->result_source_instance
+ );
+ }
+}
+
method add_additional_parent ($source) {
my ($our_pk, $their_pk) = map {
join('|',sort $_->primary_columns)
{originally_defined_in => $source->name, %{$rel_info->{attrs}}},
);
}
+ { no strict 'refs';
+ push(@{$self->result_class.'::ISA'}, $source->result_class);
+ }
+}
+
+method _source_by_name ($name) {
+ my $schema = $self->schema;
+ my ($source) =
+ grep { $_->name eq $name }
+ map $schema->source($_), $schema->sources;
+ confess "Couldn't find attached source for parent $name - did you use load_classes? This module is only compatible with load_namespaces"
+ unless $source;
+ return $source;
}
method schema (@args) {
my $ret = $self->next::method(@args);
if (@args) {
if ($self->parent_source) {
- my $schema = $self->schema;
my $parent_name = $self->parent_source->name;
- my ($parent) =
- grep { $_->name eq $parent_name }
- map $schema->source($_), $schema->sources;
- confess "Couldn't find attached source for parent $parent_name - did you use load_classes? This module is only compatible with load_namespaces"
- unless $parent;
- $self->parent_source($parent); # so our parent is the one in this schema
+ $self->parent_source($self->_source_by_name($parent_name));
}
+ $self->additional_parents([
+ map { $self->_source_by_name($_->name) }
+ @{$self->additional_parents||[]}
+ ]);
}
return $ret;
}
# have to use source name lookups rather than result class here
# because we don't actually have a result class on the raw sources
$table->add_relationship('parent', $parent->raw_source_name, \%pk_join);
- $self->depends_on->{$parent->source_name} = 1;
+ $self->deploy_depends_on->{$parent->result_class} = 1;
}
foreach my $add (@{$self->additional_parents||[]}) {
$table->add_relationship(
'parent_'.$add->name, $add->source_name, \%pk_join
);
- $self->depends_on->{$add->source_name} = 1;
+ $self->deploy_depends_on->{$add->result_class} = 1;
}
# add every column that's actually a concrete part of us
*names_of = sub (@cols) { map $_->{name}, @cols };
- *function_body = sub ($name, $args, $body_parts) {
+ *function_body = sub {
+ my ($name,$args,$body_parts) = @_;
my $arglist = join(
', ',
map "_${\$_->{name}} ${\uc($_->{data_type})}",
$function$ LANGUAGE plpgsql;
};
};
+ #*function_body = sub ($name,$args,$body_parts) {
+ #my $arglist = join(
+ #', ',
+ #map "_${\$_->{name}} ${\uc($_->{data_type})}",
+ #@$args
+ #);
+ #my $body = join("\n", '', map " $_;", @$body_parts);
+ #return strip tt q{
+ #CREATE OR REPLACE FUNCTION [% name %]
+ #([% arglist %])
+ #RETURNS VOID AS $function$
+ #BEGIN
+ #[%- body %]
+ #END;
+ #$function$ LANGUAGE plpgsql;
+ #};
+ #};
}
BEGIN {
}
1;
+
+__END__
+
+=head1 NAME
+
+DBIx::Class::ResultSource::MultipleTableInheritance
+Use multiple tables to define your classes
+
+=head1 NOTICE
+
+This only works with PostgreSQL for the moment.
+
+=head1 SYNOPSIS
+
+ {
+ package Cafe::Result::Coffee;
+
+ use strict;
+ use warnings;
+ use parent 'DBIx::Class::Core';
+ use aliased 'DBIx::Class::ResultSource::MultipleTableInheritance'
+ => 'MTI';
+
+ __PACKAGE__->table_class(MTI);
+ __PACKAGE__->table('coffee');
+ __PACKAGE__->add_columns(
+ "id", { data_type => "integer" },
+ "flavor", {
+ data_type => "text",
+ default_value => "good" },
+ );
+
+ __PACKAGE__->set_primary_key("id");
+
+ 1;
+ }
+
+ {
+ package Cafe::Result::Sumatra;
+
+ use parent 'Cafe::Result::Coffee';
+
+ __PACKAGE__->table('sumatra');
+
+ __PACKAGE__->add_columns( "aroma",
+ { data_type => "text" }
+ );
+
+ 1;
+ }
+
+ ...
+
+ my $schema = Cafe->connect($dsn,$user,$pass);
+
+ my $cup = $schema->resultset('Sumatra');
+
+ print STDERR Dwarn $cup->result_source->columns;
+
+ "id"
+ "flavor"
+ "aroma"
+ ..
+
+Inherit from this package and you can make a resultset class from a view, but
+that's more than a little bit misleading: the result is B<transparently
+writable>.
+
+This is accomplished through the use of stored procedures that map changes
+written to the view to changes to the underlying concrete tables.
+
+=head1 WHY?
+
+In many applications, many classes are subclasses of others. Let's say you
+have this schema:
+
+ # Conceptual domain model
+
+ class User {
+ has id,
+ has name,
+ has password
+ }
+
+ class Investor {
+ has id,
+ has name,
+ has password,
+ has dollars
+ }
+
+That's redundant. Hold on a sec...
+
+ class User {
+ has id,
+ has name,
+ has password
+ }
+
+ class Investor extends User {
+ has dollars
+ }
+
+Good idea, but how to put this into code?
+
+One far-too common and absolutely horrendous solution is to have a "checkbox"
+in your database: a nullable "investor" column, which entails a nullable
+"dollars" column, in the user table.
+
+ create table "user" (
+ "id" integer not null primary key autoincrement,
+ "name" text not null,
+ "password" text not null,
+ "investor" tinyint(1),
+ "dollars" integer
+ );
+
+Let's not discuss that further.
+
+A second, better, solution is to break out the two tables into user and
+investor:
+
+ create table "user" (
+ "id" integer not null primary key autoincrement,
+ "name" text not null,
+ "password" text not null
+ );
+
+ create table "investor" (
+ "id" integer not null references user("id"),
+ "dollars" integer
+ );
+
+So that investor's PK is just an FK to the user. We can clearly see the class
+hierarchy here, in which investor is a subclass of user. In DBIx::Class
+applications, this second strategy looks like:
+
+ my $user_rs = $schema->resultset('User');
+ my $new_user = $user_rs->create(
+ name => $args->{name},
+ password => $args->{password},
+ );
+
+ ...
+
+ my $new_investor = $schema->resultset('Investor')->create(
+ id => $new_user->id,
+ dollars => $args->{dollars},
+ );
+
+One can cope well with the second strategy, and it seems to be the most popular
+smart choice.
+
+=head1 HOW?
+
+There is a third strategy implemented here. Make the database do more of the
+work: hide the nasty bits so we don't have to handle them unless we really want
+to. It'll save us some typing and it'll make for more expressive code. What if
+we could do this:
+
+ my $new_investor = $schema->resultset('Investor')->create(
+ name => $args->{name},
+ password => $args->{password},
+ dollars => $args->{dollars},
+ );
+
+And have it Just Work? The user...
+
+ {
+ name => $args->{name},
+ password => $args->{password},
+ }
+
+should be created behind the scenes, and the use of either user or investor
+in your code should require no special handling. Deleting and updating
+$new_investor should also delete or update the user row.
+
+It does. User and investor are both views, their concrete tables abstracted
+away behind a set of rules and triggers. You would expect the above DBIC
+create statement to look like this in SQL:
+
+ INSERT INTO investor ("name","password","dollars") VALUES (...);
+
+But using MTI, it is really this:
+
+ INSERT INTO _user_table ("username","password") VALUES (...);
+ INSERT INTO _investor_table ("id","dollars") VALUES (currval('_user_table_id_seq',...) );
+
+For deletes, the triggers fire in reverse, to preserve referential integrity
+(foreign key constraints). For instance:
+
+ my $investor = $schema->resultset('Investor')->find({id => $args->{id}});
+ $investor->delete;
+
+Becomes:
+
+ DELETE FROM _investor_table WHERE ("id" = ?);
+ DELETE FROM _user_table WHERE ("id" = ?);
+
+
+=head1 METHODS
+
+=over
+
+=item new
+
+
+MTI find the parents, if any, of your resultset class and adds them to the
+list of parent_sources for the table.
+
+
+=item add_additional_parents
+
+
+Continuing with coffee:
+
+ __PACKAGE__->result_source_instance->add_additional_parents(
+ qw/
+ MyApp::Schema::Result::Beverage
+ MyApp::Schema::Result::Liquid
+ /
+ );
+
+This just lets you manually add additional parents beyond the ones MTI finds.
+
+=item add_additional_parent
+
+ __PACKAGE__->result_source_instance->add_additional_parent(
+ MyApp::Schema::Result::Beverage
+ );
+
+You can also add just one.
+
+=item attach_additional_sources
+
+MTI takes the parents' sources and relationships, creates a new
+DBIx::Class::Table object from them, and registers this as a new, raw, source
+in the schema, e.g.,
+
+ use MyApp::Schema;
+
+ print STDERR map { "$_\n" } MyApp::Schema->sources;
+
+ # Coffee
+ # Beverage
+ # Liquid
+ # Sumatra
+ # Raw::Sumatra
+
+Raw::Sumatra will be used to generate the view.
+
+=item view_definition
+
+This takes the raw table and generates the view (and stored procedures) you will use.
+
+=back
+
+=head1 AUTHOR
+
+Matt S. Trout, E<lt>mst@shadowcatsystems.co.ukE<gt>
+
+=head2 CONTRIBUTORS
+
+Amiri Barksdale, E<lt>amiri@metalabel.comE<gt>
+
+=head1 COPYRIGHT
+
+Copyright (c) 2010 the DBIx::Class::ResultSource::MultipleTableInheritance
+L</AUTHOR> and L</CONTRIBUTORS> as listed above.
+
+=head1 LICENSE
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
+
+=head1 SEE ALSO
+
+L<DBIx::Class>
+L<DBIx::Class::ResultSource>
+
+=cut
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