=head1 NAME
-DBIx::Class::Manual::Cookbook - Misc receipes
+DBIx::Class::Manual::Cookbook - Miscellaneous recipes
-=over 4
+=head1 RECIPES
-=item Input validation.
+=head2 Complex searches
-=item Using joins
+Sometimes you need to formulate a query using specific operators:
-=item Many-to-many relationships
+ my @albums = MyApp::DB::Album->search({
+ artist => { 'like', '%Lamb%' },
+ title => { 'like', '%Fear of Fours%' },
+ });
-This is not as easy as it could be, but it's possible. Here's an example to
-illustrate:
+This results in something like the following C<WHERE> clause:
- # Set up inherited connection information
- package MyApp::DBIC;
- use base qw/DBIx::Class/;
+ WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%'
- __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
- __PACKAGE__->connection(...);
+Other queries might require slightly more complex logic:
- # Set up a class for the 'authors' table
- package MyApp::DBIC::Author;
- use base qw/MyApp::DBIC/;
+ my @albums = MyApp::DB::Album->search({
+ -or => [
+ -and => [
+ artist => { 'like', '%Smashing Pumpkins%' },
+ title => 'Siamese Dream',
+ ],
+ artist => 'Starchildren',
+ ],
+ });
- __PACKAGE__->table('authors');
- __PACKAGE__->add_columns(qw/authID first_name last_name/);
- __PACKAGE__->set_primary_key(qw/authID/);
+This results in the following C<WHERE> clause:
- # Define relationship to the link table
- __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'authID');
+ WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' )
+ OR artist = 'Starchildren'
- # Create the accessor for books from the ::Author class
- sub books {
- my ($self) = @_;
- return MyApp::DBIC::Book->search(
- { 'b2a.authID' => $self->authID }, # WHERE clause
- { join => 'b2a' } # join condition (part of search attrs)
- # 'b2a' refers to the relationship named earlier in the Author class.
- # 'b2a.authID' refers to the authID column of the b2a relationship,
- # which becomes accessible in the search by being joined.
- );
- }
+For more information on generating complex queries, see
+L<SQL::Abstract/WHERE CLAUSES>.
- # define the link table class
- package MyApp::DBIC::Book2Author;
- use base qw/MyApp::DBIC/;
+=head2 Disconnecting cleanly
- __PACKAGE__->table('book2author');
- __PACKAGE__->add_columns(qw/bookID authID/);
- __PACKAGE__->set_primary_key(qw/bookID authID/);
+If you find yourself quitting an app with Control-C a lot during
+development, you might like to put the following signal handler in
+your main database class to make sure it disconnects cleanly:
- __PACKAGE__->belongs_to('authID' => 'MyApp::DBIC::Author');
- __PACKAGE__->belongs_to('bookID' => 'MyApp::DBIC::Book');
+ $SIG{INT} = sub {
+ __PACKAGE__->storage->dbh->disconnect;
+ };
- package MyApp::DBIC::Book;
- use base qw/MyApp::DBIC/;
+=head2 Using joins and prefetch
- __PACKAGE__->table('books');
- __PACKAGE__->add_columns(qw/bookID title edition isbn publisher year/);
- __PACKAGE__->set_primary_key(qw/bookID/);
-
- __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'bookID');
+See L<DBIx::Class::ResultSet/ATTRIBUTES>.
- sub authors {
- my ($self) = @_;
- return MyApp::DBIC::Author->search(
- { 'b2a.bookID' => $self->bookID }, # WHERE clause
- { join => 'b2a' }); # join condition (part of search attrs)
- }
+=head2 Transactions
- # So the above search returns an author record where the bookID field of the
- # book2author table equals the bookID of the books (using the bookID
- # relationship table
+As of version 0.04001, there is improved transaction support in
+L<DBIx::Class::Storage::DBI>. Here is an example of the recommended
+way to use it:
-=item Advanced Exception handling
+ my $genus = Genus->find(12);
+ eval {
+ MyDB->txn_begin;
+ $genus->add_to_species({ name => 'troglodyte' });
+ $genus->wings(2);
+ $genus->update;
+ cromulate($genus); # Can have a nested transation
+ MyDB->txn_commit;
+ };
+ if ($@) {
+ # Rollback might fail, too
+ eval {
+ MyDB->txn_rollback
+ };
+ }
-=item Transactions
+Currently, a nested commit will do nothing and a nested rollback will
+die. The code at each level must be sure to call rollback in the case
+of an error, to ensure that the rollback will propagate to the top
+level and be issued. Support for savepoints and for true nested
+transactions (for databases that support them) will hopefully be added
+in the future.
-=back
+=head2 Many-to-many relationships
+
+This is not as easy as it could be, but it's possible. Here's an
+example to illustrate:
+
+ # Set up inherited connection information
+ package MyApp::DBIC;
+ use base qw/DBIx::Class/;
+
+ __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
+ __PACKAGE__->connection(...);
+
+ # Set up a class for the 'authors' table
+ package MyApp::DBIC::Author;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('authors');
+ __PACKAGE__->add_columns(qw/authID first_name last_name/);
+ __PACKAGE__->set_primary_key(qw/authID/);
+
+ # Define relationship to the link table
+ __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'authID');
+
+ # Create the accessor for books from the Author class
+ sub books {
+ my ($self) = @_;
+ return MyApp::DBIC::Book->search(
+ { 'b2a.authID' => $self->authID }, # WHERE clause
+ { join => 'b2a' } # join condition (part of search attrs)
+ # 'b2a' refers to the relationship named earlier in the Author class.
+ # 'b2a.authID' refers to the authID column of the b2a relationship,
+ # which becomes accessible in the search by being joined.
+ );
+ }
+
+ # Define the link table class
+ package MyApp::DBIC::Book2Author;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('book2author');
+ __PACKAGE__->add_columns(qw/bookID authID/);
+ __PACKAGE__->set_primary_key(qw/bookID authID/);
+
+ __PACKAGE__->belongs_to('authID' => 'MyApp::DBIC::Author');
+ __PACKAGE__->belongs_to('bookID' => 'MyApp::DBIC::Book');
+
+ package MyApp::DBIC::Book;
+ use base qw/MyApp::DBIC/;
+
+ __PACKAGE__->table('books');
+ __PACKAGE__->add_columns(qw/bookID title edition isbn publisher year/);
+ __PACKAGE__->set_primary_key(qw/bookID/);
+
+ __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'bookID');
+
+
+ # Returns an author record where the bookID field of the
+ # book2author table equals the bookID of the books (using the
+ # bookID relationship table)
+ sub authors {
+ my ($self) = @_;
+ return MyApp::DBIC::Author->search(
+ { 'b2a.bookID' => $self->bookID }, # WHERE clause
+ { join => 'b2a' } # JOIN condition
+ );
+ }
+
+=head2 Setting default values
+
+It's as simple as overriding the C<new> method. Note the use of
+C<next::method>.
+
+ sub new {
+ my ( $class, $attrs ) = @_;
+
+ $attrs->{foo} = 'bar' unless defined $attrs->{foo};
+
+ $class->next::method($attrs);
+ }
+
+=head2 Stringification
+
+Employ the standard stringification technique by using the C<overload>
+module. Replace C<foo> with the column/method of your choice.
+
+ use overload '""' => 'foo', fallback => 1;
+
+=cut
projects / dbsrgits/DBIx-Class-Historic.git / blobdiff