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64 <h1>DBIx::Class Introduction</h1>
65 <h2>YAPC::NA 2010</h2>
69 <div class="presentation">
72 <h1>DBIX::Class (aka DBIC)</h1>
73 <h3>for (advanced) beginners</h3>
78 <h4>Originally Leo Lapworth @ LPW 2009</h4>
79 <h4>Matthew S. Trout</h4>
80 <h4>Justin D. Hunter</h4>
81 <h4>Arthur Axel "fREW" Schmidt</h4>
86 <p>You know a little about Perl and using objects</p>
87 <p>You know a little bit about databases and using foreign keys</p>
90 <li>How many people have designed a database with Foreign Keys?</li>
91 <li>How many people have used any ORM?<ul>
94 <li> Class::DBI? </li>
100 <li> DataMapper? </li>
101 <li>(N)Hibernate?</li>
108 <h1>DBIx::Class?</h1>
110 <li>ORM (object relational mapper)</li>
111 <li>SQL <-> OO (using objects instead of SQL)</li>
112 <li>Simple, powerful, complex, fab and confusing</li>
113 <li>There are many ORMs, DBIx::Class just happens to be the best in Perl (personal opinion)</li>
118 <h1>point of note</h1>
119 <p><em>"Debugging is twice as hard as writing the code in the first
120 place. Therefore, if you write the code as cleverly as possible,
121 you are, by definition, not smart enough to debug it." - Brian
122 W. Kernighan</em></p>
124 <p>This talk is about making it easy so we are less likely to get
129 <h1>Examples Table Setup</h1>
134 <em>MySQL not recommended</em>
138 <h1>authors table</h1>
139 <pre>CREATE TABLE authors(
140 id int(8) primary key auto_increment,
142 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
147 <p>Name tables as simple plurals (<strong>add an S</strong>) - makes relationships easier to understand</p>
148 <p>Use a character set (<strong>UTF8</strong>) from the start (for international characters)</p>
152 <h1>authors table</h1>
153 <pre>CREATE TABLE author<strong>s</strong>(
154 id int(8) primary key auto_increment,
156 ) engine = <strong>InnoDB</strong> DEFAULT CHARSET=<strong>utf8</strong>;</pre>
161 <pre>CREATE TABLE books(
162 id int(8) primary key auto_increment,
164 author_id int(8),foreign key (author)
165 references authors(id)
166 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
172 <p>Name link fields as singular</p>
173 <p>Ensure foreign key is the same type and size in both tables</p>
178 <pre>CREATE TABLE books(
179 id int(8) primary key auto_increment,
181 author_id <strong>int(8)</strong>,<strong>foreign key (<em>author</em>)</strong>
182 <strong>references <em>authors(id)</em></strong>
183 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
187 <h1>CRUD compared</h1>
189 <li><strong>C</strong> - Create</li>
190 <li><strong>R</strong> - Read</li>
191 <li><strong>U</strong> - Update</li>
192 <li><strong>D</strong> - Delete</li>
197 <h1>Manual (SQL)</h1>
202 <pre>my $sth = $dbh->prepare('
209 'A book title', $author_id
215 <pre>my $sth = $dbh->prepare('
217 authors.name as author_name
219 WHERE books.author = authors.id
225 <pre>while( my $book = $sth->fetchrow_hashref() ) {
229 . $book->{author_name}
236 <pre>my $update = $dbh->prepare('
243 'New title',<strong>$book_id</strong>
249 <pre>my $delete = $dbh->prepare('
254 $delete->execute(<strong>$book_id</strong>);</pre>
262 <h1>DBIC: Create</h1>
263 <pre>my $book = $book_model->create({
264 title => 'A book title',
265 author => $author_id,
267 <p>Look ma, no SQL!</p>
271 <h1>DBIC: Create</h1>
272 <pre>my $pratchett = $author_model->create({
273 name => 'Terry Pratchett',
278 <h1>DBIC: Create</h1>
279 <pre>my $book = $pratchett->create_related(
280 <strong>books</strong> => {
281 title => 'Another Discworld book',
284 <pre>my $book = $pratchett->add_to_<strong>books</strong>({
285 title => 'Another Discworld book',
291 <p>DBIx::Class - Lots of ways to do the same thing...</p>
292 <p><em>"There is more than one way to do it (TIMTOWTDI, usually pronounced "Tim Toady") is a Perl motto"</em></p>
297 <pre>my $book = $book_model->find($book_id);
299 my $book = $book_model->search({
300 title => 'A book title',
301 }, { rows => 1 })->single;
303 my @books = $book_model->search({
304 author => $author_id,
310 <pre>while( my $book = $books_rs->next ) {
314 . $book->author->name
321 <pre>my $books_rs = $book_rs->search({
322 author => $author_id,
324 <p>Search takes SQL::Abstract formatted queries</p>
325 <pre>> perldoc SQL::Abstract</p>
329 <h1>DBIC: Update</h1>
330 <pre>$book->update({
331 title => 'New title',
336 <h1>DBIC: Delete</h1>
337 <pre>$book->delete;</pre>
341 <h1>Creating models</h1>
345 <pre>package Foo::Schema::Result::Author;
346 use strict; use warnings;
347 __PACKAGE__->table('authors');
348 __PACKAGE__->add_columns(
350 data_type => 'int',
354 data_type => 'varchar',
359 __PACKAGE__->set_primary_key('id');
360 __PACKAGE__->has_many( books =>
361 'Foo::Schema::Result::Book', 'author_id'
368 <pre>package Foo::Schema::Result::Book;
369 use strict; use warnings;
370 __PACKAGE__->table('books');
371 __PACKAGE__->add_columns(
373 data_type => 'int',
377 data_type => 'varchar',
382 data_type => 'int',
384 is_nullable => 1, # <-- probably should be 0
387 __PACKAGE__->set_primary_key('id');
388 __PACKAGE__->belongs_to( author =>
389 'Foo::Schema::Result::Author', 'author_id'
396 <h1>Schema::Loader</h1>
397 <p>DB -> Perl vs Perl -> DB</p>
398 <pre>package Foo::Schema;
399 use strict; use warnings;
400 use base 'DBIx::Class::Schema::Loader';
401 __PACKAGE__->loader_options({
403 debug => $ENV{DBIC_TRACE},
409 my $schema = Foo::Schema->connect($dsn, $user, $pass);
414 <h1>Splitting Logic Cleanly</h1>
415 <p>Foo::Schema::Result::Bar = individual row</p>
416 <p>Foo::Schema::ResultSet::Bar = searches / table </p>
420 <h1>Using your Schema</h1>
422 use strict; use warnings;
425 my $schema = Foo::Schema->connect($dns, $user, $pass);
426 my $author_rs = $schema->resultset('Author');
427 my $author = $author_rs->create({
428 name => 'Douglas Adams',
430 my $book = $author->add_to_books({
438 <pre>DBIC_TRACE=1 ./your_script.pl</pre>
442 <h1>SQL - debugging</h1>
443 <pre>INSERT INTO authors (name)
444 VALUES (?): 'Douglas Adams'
446 INSERT INTO books (author, title)
447 VALUES (?, ?): '5', '42'</pre>
452 <pre>Foo::Schema::Result::Book
453 Foo::Schema::ResultSet::Book
454 Foo::Schema::Result::Author
455 Foo::Schema::ResultSet::Book</pre>
460 <pre>package Foo::Schema::Result::Book;
461 use base 'DBIx::Class::Core';
470 # search amazon or something
471 my $api = Amazon::API->book({
472 title => $self->title
475 return $api->isbn;
483 <pre>print $book->isbn;</pre>
487 <h1>Result:: (inflating)</h1>
488 <pre>package Foo::Schema::Result::Book;
489 use base 'DBIx::Class::Core';
495 __PACKAGE__->load_components('InflateColumn');
496 use DateTime::Format::MySQL;
498 __PACKAGE__-><strong>inflate_column</strong>(
499 <strong>date_published</strong> => {
500 inflate => sub { DateTime::Format::MySQL->parse_date(shift) },
501 deflate => sub { shift->ymd},
504 # Automatic see: DBIx::Class::InflateColumn::DateTime</pre>
508 <h1>Result:: (deflating)</h1>
509 <pre>$book->date_published(DateTime->now);
510 $book->update;</pre>
514 <h1>Result:: (inflating)</h1>
515 <pre>my $date_published = $book->date_published;
516 print $date_published->month_abbr;</pre>
518 <strong><em>Nov</em></strong>
522 <h1>ResultSets::</h1>
523 <pre>package Foo::Schema::ResultSet::Books;
524 use base 'DBIx::Class::ResultSet';
525 sub the_ultimate_books {
527 return $self->search({ title => { -like => '%42%' } });
530 my ( $self, $author ) = @_;
531 return $self->search({ author => $author->id })
538 <h1>ResultSets::</h1>
539 <pre>use Foo::Schema;
540 my $schema = Foo::Schema->connect(...);
541 my $book_rs = Foo::Schema->resultset('Book');
542 my $book_search = $book_rs->the_ultimate_books;
543 my @books = $book_search->all;</pre>
547 <h1>ResultSets: Chaining</h1>
549 my $book_rs = $schema->resultset('Book');
550 my $author_rs = $schema->resultset('Author');
551 my $author = $author_model->search({ name => 'Douglas Adams' })->single;
552 my $book_rs = $book_model->the_ultimate_books->by_author($author);
553 my @books = $book_rs->all;</pre>
557 <h1>ResultSets: Chaining</h1>
558 <pre>$book_rs = $schema->resultset('Book')
559 ->the_ultimate_books
560 ->by_author($author);</pre>
563 <pre>my $book_rs = $schema->resultset('Book')
564 ->the_ultimate_books;
565 $book_rs = $book_rs->by_author($author);</pre>
568 # SELECT me.id, me.title, me.date_published, me.author
570 # WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'
571 # WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'</pre>
575 <h1>ResultSets::chaining</h1>
576 <pre>my $rs = $book_model
577 ->category('childrens')
578 ->by_author($author)
579 ->published_after('1812')
580 ->first_page_contains('once upon')
581 ->rating_greater_than(4);
583 my @books = $rs->all;</pre>
587 <h1>overloading before new record</h1>
588 <pre>package Foo::Schema::Result::Author;
589 use base 'DBIx::Class::Core';
592 my ( $class, $attrs ) = @_;
594 my $new = $class->next::method($attrs);
601 <h1>relationships</h1>
605 <h1>multiple authors</h1>
609 <h1>a few relationships</h1>
610 (authors -- author_link_to_book -- books)
614 <h1>a few relationships</h1>
619 <h1>new join table</h1>
620 <pre>CREATE TABLE author_and_books(
621 id int(8) primary key auto_increment,
624 foreign key (book) references books(id),
625 foreign key (author) references authors(id)
626 ) engine = InnoDB DEFAULT CHARSET=utf8;
628 ALTER TABLE `books` DROP `author`</pre>
632 <h1>new join table</h1>
633 <pre>CREATE TABLE author_and_books(
634 id int(8) primary key auto_increment,
637 <strong>foreign key (book) references books(id),
638 foreign key (author) references authors(id)</strong>
639 ) engine = InnoDB DEFAULT CHARSET=utf8;
641 ALTER TABLE `books` DROP `author`</pre>
650 <pre>package Foo::Schema::<strong>Result::Books</strong>;
652 __PACKAGE__->has_many( author_and_books => "Foo::Schema::Result::AuthorAndBooks",
653 { "foreign.book" => "self.id" },
656 <strong># This is auto generated by Schema::Loader</strong></pre>
661 <pre>package Foo::Schema::<strong>Result::Books</strong>;
663 __PACKAGE__->has_many(
664 author_and_books => <strong># name of accessor</strong>
665 "Foo::Schema::Result::AuthorAndBooks", <strong># related class</strong>
666 { "foreign.book" => "self.id" } <strong># Relationship (magic often works if not
667 # specified, but avoid!)</strong>
678 <pre>package Foo::Schema::<strong>Result::AuthorAndBooks</strong>;
680 __PACKAGE__->belongs_to(
681 book => <strong># Accessor name</strong>
682 "Foo::Schema::Result::Books", <strong># Related class</strong>
683 { id => "book" } <strong># relationship</strong>
689 <h1>same for Authors</h1>
693 <h1>with no coding...</h1>
697 <h1>many_to_many</h1>
701 <h1>many_to_many</h1>
702 <pre>package Foo::Schema::<strong>Result::Book</strong>;
703 use base 'DBIx::Class::Core';
705 __PACKAGE__->many_to_many(
706 authors => "author_and_books", 'author'
711 <strong> # This is <em>NOT</em> auto generated by Schema::Loader </strong></pre>
715 <h1>many_to_many</h1>
716 <pre>package Foo::Schema::<strong>Result::Book</strong>;
717 use base 'DBIx::Class::Core';
719 __PACKAGE__->many_to_many(
720 authors <strong># Accessor name</strong>
721 => "author_and_books", <strong># has_many</strong>
722 'author' <strong># foreign relationship name</strong>
729 <h1>many_to_many</h1>
730 <pre>package Foo::Schema::Result::Author;
731 use base 'DBIx::Class::Core';
733 __PACKAGE__->many_to_many(
734 "books" <strong># Accessor Name</strong>
735 => "author_and_books", <strong># has_many accessor_name</strong>
736 'book' <strong># foreign relationship name</strong>
741 <strong># This is <em>NOT</em> auto generated by Schema::Loader</strong></pre>
745 <h1>using many_to_many</h1>
750 my $author_model = Foo::Schema->resultset('Authors');
751 my $author = $author_model->search({
752 name => 'Douglas Adams',
754 $author->add_to_books({
755 title => 'A new book',
760 <h1>using many_to_many</h1>
761 <pre>my $author = $author_model->search({
762 name => 'Douglas Adams',
764 <strong>$author->add_to_books({
765 title => 'A new book',
768 # SELECT me.id, me.name FROM authors me
769 # WHERE ( name = ? ): 'Douglas Adams';
770 # INSERT INTO books (title) VALUES (?): 'A new book';
771 # INSERT INTO author_and_books (author, book)
772 # VALUES (?, ?): '5', '2';</pre>
776 <h1>using many_to_many</h1>
777 <pre>$author->add_to_books($book);
779 $book->add_to_authors($author_1);
780 $book->add_to_authors($author_2);</pre>
784 <h1>in 16 lines of code</h1>
789 <p>Read them closely!</p>
793 <h1>error messages</h1>
794 <pre>DBIx::Class::Schema::Loader::connection(): Failed to load external class definition for 'Foo::Schema::Result::Authors': Can't locate object method "many_to_many" via package "Foo::Schema::Result::Author" at lib/Foo/Schema/Result/Authors.pm line 9.Compilation failed in require at /Library/Perl/5.8.8/DBIx/Class/Schema/Loader/Base.pm line 292.</pre>
798 <h1>error messages</h1>
799 <pre>DBIx::Class::Schema::Loader::connection(): Failed to load external class definition for 'Foo::Schema::Result::Authors': Can't locate object method "many_to_many" via package "Foo::Schema::<strong>Result::Author</strong>" at lib/Foo/Schema/<strong>Result/Authors.pm</strong> line 9.Compilation failed in require at /Library/Perl/5.8.8/DBIx/Class/Schema/Loader/Base.pm line 292.</pre>
805 <li>Turn on debugging</li>
806 <li>Read error messages (sometimes useful!)</li>
807 <li>Check field names</li>
808 <li>Check package names</li>
809 <li>Check which database you are connected to (dev/test/live?) - repeat above</li>
814 <h1>bonus slides!</h1>
818 <h1>Template Toolkit</h1>
820 <li><pre>[% author.books.count %]</pre> not working?</li>
821 <li>TT all methods are called in list context</li>
822 <li><pre>[% author.books<strong>_rs</strong>.count %]</pre> scalar context</li>
823 <li><em>Available for all relationships</em></li>
829 <pre>package Your::App::Model::<strong>Foo</strong>;
830 use base qw(<strong>Catalyst::Model::Schema::Schema</strong>);
835 __PACKAGE__->config(
836 schema_class => '<strong>Foo::Schema</strong>',
840 <p>Keep your Schema in a <em>separate</em> package to your Catalyst application</p>
845 <pre>sub action_name : Local {
848 my $model = $c->model('Schema::Foo');
849 my $author_model = $model->resultset('Authors');