lib/DBIx/Class/Manual/Cookbook.pod

   1 =head1 NAME
   2
   3 DBIx::Class::Manual::Cookbook - Misc receipes
   4
   5 =over 4
   6
   7 =item Input validation.
   8
   9 =item Using joins
  10
  11 =item Many-to-many relationships
  12
  13 This is not as easy as it could be, but it's possible. Here's an example to
  14 illustrate:
  15
  16         # Set up inherited connection information
  17         package MyApp::DBIC;
  18
  19         use base qw/DBIx::Class/;
  20
  21         __PACKAGE__->load_components(qw/PK::Auto::SQLite Core DB/);
  22         __PACKAGE__->connection(...);
  23
  24         # Set up a class for the 'authors' table
  25         package MyApp::DBIC::Author;
  26         use base qw/MyApp::DBIC/;
  27
  28         __PACKAGE__->table('authors');
  29         __PACKAGE__->add_columns(qw/authID first_name last_name/);
  30         __PACKAGE__->set_primary_key(qw/authID/);
  31
  32         # Define relationship to the link table
  33         __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'authID');
  34
  35         # Create the accessor for books from the ::Author class
  36         sub books {
  37           my ($self) = @_;
  38           return MyApp::DBIC::Book->search(
  39                 { 'b2a.authID' => $self->authID }, { join => 'b2a' }
  40           );
  41             # 'b2a' refers to the relationship named earlier in the Author class.
  42                 # 'b2a.authID' refers to the authID column of the b2a relationship,
  43                 # which becomes accessible in the search by being joined.
  44         }
  45
  46         # define the link table class
  47         package MyApp::DBIC::Book2Author;
  48
  49         use base qw/MyApp::DBIC/;
  50
  51         __PACKAGE__->table('book2author');
  52         __PACKAGE__->add_columns(qw/bookID authID/);
  53         __PACKAGE__->set_primary_key(qw/bookID authID/);
  54
  55         __PACKAGE__->belongs_to('authID' => 'MyApp::DBIC::Author');
  56         __PACKAGE__->belongs_to('bookID' => 'MyApp::DBIC::Book');
  57
  58         package MyApp::DBIC::Book;
  59
  60         use base qw/MyApp::DBIC/;
  61
  62         __PACKAGE__->table('books');
  63         __PACKAGE__->add_columns(qw/bookID title edition isbn publisher year/);
  64         __PACKAGE__->set_primary_key(qw/bookID/);
  65
  66         __PACKAGE__->has_many('b2a' => 'MyApp::DBIC::Book2Author', 'bookID');
  67
  68         sub authors {
  69          my ($self) = @_;
  70          return MyApp::DBIC::Author->search(
  71            { 'b2a.bookID' => $self->bookID }, # WHERE clause
  72            { join => 'b2a' }); # Join condition
  73         }
  74
  75         # So the above search returns an author record where the bookID field of the
  76         # book2author table equals the bookID of the books (using the bookID
  77         # relationship table
  78
  79 =item Advanced Exception handling
  80
  81 =item Transactions
  82
  83 =back