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) {
}
1;
+
+__END__
+=head1 NAME
+
+DBIx::Class::ResultSource::MultipleTableInheritance -- Use multiple tables to define your classes
+
+=head1 SYNOPSIS
+
+ {
+ package MyApp::Schema::Result::Coffee;
+
+ __PACKAGE__->table_class('DBIx::Class::ResultSource::MultipleTableInheritance');
+ __PACKAGE__->table('coffee');
+ __PACKAGE__->add_columns(
+ "id",
+ {
+ data_type => "integer",
+ default_value => "nextval('coffee_seq'::regclass)",
+ is_auto_increment => 1,
+ is_foreign_key => 1,
+ is_nullable => 0,
+ size => 4,
+ },
+ "flavor",
+ {
+ data_type => "text",
+ default_value => "good",
+ },
+ );
+
+ __PACKAGE__->set_primary_key("id");
+
+ 1;
+ }
+
+ {
+ package MyApp::Schema::Result::Sumatra;
+
+ use parent 'Coffee';
+
+ __PACKAGE__->table('sumatra');
+
+ __PACKAGE__->add_columns(
+ "aroma",
+ {
+ data_type => "text",
+ default_value => undef,
+ is_nullable => 0,
+ },
+ );
+
+ 1;
+ }
+
+ ...
+
+ my $schema = MyApp::Schema->connect($dsn);
+
+ my $cup = $schema->resultset('Sumatra')->new;
+
+ print STDERR Dumper $cup->columns;
+
+ $VAR1 = 'id';
+ $VAR2 = 'flavor';
+ $VAR3 = '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}});
+ $investor->delete;
+
+Becomes:
+
+ DELETE FROM _investor_table WHERE ("id" = ?);
+ DELETE FROM _user_table WHERE ("id" = ?);
+
+
+=head1 METHODS
+
+=over
+
+=item new
+
+
+MTI find the parents, if any, of your resultset class and adds them to the list of parent_sources for the table.
+
+
+=item add_additional_parents
+
+
+Continuing with coffee:
+
+ __PACKAGE__->result_source_instance->add_additional_parents(
+ qw/
+ MyApp::Schema::Result::Beverage
+ MyApp::Schema::Result::Liquid
+ /
+ );
+
+This just lets you manually add additional parents beyond the ones MTI finds.
+
+=item add_additional_parent
+
+ __PACKAGE__->result_source_instance->add_additional_parent(
+ MyApp::Schema::Result::Beverage
+ );
+
+You can also add just one.
+
+=item attach_additional_sources
+
+MTI takes the parents' sources and relationships, creates new DBIx::Class:Table object from them, and registers this as a new, raw, source in the schema, e.g.,
+
+ use MyApp::Schema;
+
+ print STDERR map { "$_\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
+
+Docs: Amiri Barksdale, E<lt>amiri@metalabel.comE<gt>
+
+=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
projects / dbsrgits/DBIx-Class-ResultSource-MultipleTableInheritance.git / blobdiff