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<title>DBIx::Class (aka DBIC)</title>
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   <div id="header"></div>
   <div id="footer">
      <h1>DBIx::Class Introduction</h1>
      <h2>YAPC::NA 2010</h2>
   </div>
</div>

<div class="presentation">

   <div class="slide">
      <h1>DBIX::Class (aka DBIC)</h1>
      <h3>for (advanced) beginners</h3>
   </div>

   <div class="slide">
      <h1>Authors</h1>
      <h4>Originally Leo Lapworth @ LPW 2009</h4>
      <h4>Matthew S. Trout</h4>
      <h4>Justin D. Hunter</h4>
      <h4>Arthur Axel "fREW" Schmidt</h4>
   </div>

   <div class="slide">
      <h1>assumptions</h1>
      <p>You know a little about Perl and using objects</p>
      <p>You know a little bit about databases and using foreign keys</p>
      <div class="notes">
         <ul>
            <li>How many people have designed a database with Foreign Keys?</li>
            <li>How many people have used any ORM?<ul>
               <li>In Perl?<ul>
                  <li>DBIC?</li>
                  <li> Class::DBI? </li>
                  <li> Rose::DB?  </li>
                  <li> Fey?  </li>
                  <li> Others?  </li>
               </ul></li>
               <li>AR? </li>
               <li> DataMapper?  </li>
               <li>(N)Hibernate?</li>
            </ul></li>
         </ul>
      </div>
   </div>

   <div class="slide">
      <h1>DBIx::Class?</h1>
      <ul>
         <li>ORM (object relational mapper)</li>
         <li>SQL &lt;-&gt; OO (using objects instead of SQL)</li>
         <li>Simple, powerful, complex, fab and confusing</li>
         <li>There are many ORMs, DBIx::Class just happens to be the best in Perl (personal opinion)</li>
      </ul>
   </div>

   <div class="slide">
      <h1>point of note</h1>
      <p><em>"Debugging is twice as hard as writing the code in the first
      place. Therefore, if you write the code as cleverly as possible,
      you are, by definition, not smart enough to debug it." - Brian
      W. Kernighan</em></p>

      <p>This talk is about making it easy so we are less likely to get
      confused</p>
   </div>

   <div class="slide">
      <h1>Examples Table Setup</h1>
      <ul>
         <li>Authors</li>
         <li>Books</li>
      </ul>
      <em>MySQL not recommended</em>
   </div>

   <div class="slide">
      <h1>authors table</h1>
<pre>CREATE TABLE authors(
   id   int(8) primary key auto_increment,
   name varchar(255)
) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
   </div>

   <div class="slide">
      <h1>tips</h1>
      <p>Name tables as simple plurals (<strong>add an S</strong>) - makes relationships easier to understand</p>
      <p>Use a character set (<strong>UTF8</strong>) from the start (for international characters)</p>
   </div>

   <div class="slide">
      <h1>authors table</h1>
<pre>CREATE TABLE author<strong>s</strong>(
   id   int(8) primary key auto_increment,
   name varchar(255)
) engine = <strong>InnoDB</strong> DEFAULT CHARSET=<strong>utf8</strong>;</pre>
   </div>

   <div class="slide">
      <h1>books table</h1>
<pre>CREATE TABLE books(
   id        int(8) primary key auto_increment,
   title     varchar(255),
   author_id int(8),foreign key (author)
      references authors(id)
) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
   </div>


   <div class="slide">
      <h1>tips</h1>
      <p>Name link fields as singular</p>
      <p>Ensure foreign key is the same type and size in both tables</p>
   </div>

   <div class="slide">
      <h1>books table</h1>
<pre>CREATE TABLE books(
   id        int(8) primary key auto_increment,
   title     varchar(255),
   author_id <strong>int(8)</strong>,<strong>foreign key (<em>author</em>)</strong>
      <strong>references <em>authors(id)</em></strong>
) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
   </div>

   <div class="slide">
      <h1>CRUD compared</h1>
      <ul>
         <li><strong>C</strong> - Create</li>
         <li><strong>R</strong> - Read</li>
         <li><strong>U</strong> - Update</li>
         <li><strong>D</strong> - Delete</li>
      </ul>
   </div>

   <div class="slide">
      <h1>Manual (SQL)</h1>
   </div>

   <div class="slide">
      <h1>SQL: Create</h1>
<pre>my $sth = $dbh-&gt;prepare('
   INSERT INTO books
   (title, author)
   values (?,?)
');

$sth-&gt;execute(
  'A book title', $author_id
);</pre>
   </div>

   <div class="slide">
      <h1>SQL: Read</h1>
<pre>my $sth = $dbh-&gt;prepare('
   SELECT title,
   authors.name as author_name
   FROM books, authors
   WHERE books.author = authors.id
');</pre>
   </div>

   <div class="slide">
      <h1>SQL: Read</h1>
<pre>while( my $book = $sth-&gt;fetchrow_hashref() ) {
  print 'Author of '
     . $book-&gt;{title}
     . ' is '
     . $book-&gt;{author_name}
     . "\n";
}</pre>
   </div>

   <div class="slide">
      <h1>SQL: Update</h1>
<pre>my $update = $dbh-&gt;prepare('
   UPDATE books
   SET title = ?
   WHERE id = ?
');

$update-&gt;execute(
  'New title',<strong>$book_id</strong>
);</pre>
   </div>

   <div class="slide">
      <h1>SQL: Delete</h1>
<pre>my $delete = $dbh-&gt;prepare('
   DELETE FROM books
   WHERE id = ?
');

$delete-&gt;execute(<strong>$book_id</strong>);</pre>
   </div>

   <div class="slide">
      <h1>DBIx::Class</h1>
   </div>

   <div class="slide">
      <h1>DBIC: Create</h1>
<pre>my $book = $book_model-&gt;create({
   title  =&gt; 'A book title',
   author =&gt; $author_id,
});</pre>
      <p>Look ma, no SQL!</p>
   </div>

   <div class="slide">
      <h1>DBIC: Create</h1>
<pre>my $pratchett = $author_model-&gt;create({
   name =&gt; 'Terry Pratchett',
});</pre>
   </div>

   <div class="slide">
      <h1>DBIC: Create</h1>
<pre>my $book = $pratchett-&gt;create_related(
  <strong>books</strong> =&gt; {
   title =&gt; 'Another Discworld book',
});</pre>
<strong>or</strong>
<pre>my $book = $pratchett-&gt;add_to_<strong>books</strong>({
   title =&gt; 'Another Discworld book',
});</pre>
   </div>

   <div class="slide">
      <h1>DBIC: Read</h1>
      <p>DBIx::Class - Lots of ways to do the same thing...</p>
      <p><em>"There is more than one way to do it (TIMTOWTDI, usually pronounced "Tim Toady") is a Perl motto"</em></p>
   </div>

   <div class="slide">
      <h1>DBIC: Read</h1>
<pre>my $book = $book_model-&gt;find($book_id);

my $book = $book_model-&gt;search({
   title =&gt; 'A book title',
}, { rows =&gt; 1 })-&gt;single;

my @books = $book_model-&gt;search({
   author =&gt; $author_id,
})-&gt;all;</pre>
   </div>

   <div class="slide">
      <h1>DBIC: Read</h1>
<pre>while( my $book = $books_rs-&gt;next ) {
 print 'Author of '
    . $book-&gt;title
    . ' is '
    . $book-&gt;author-&gt;name
    . "\n";
}</pre>
   </div>

   <div class="slide">
      <h1>DBIC: Read</h1>
<pre>my $books_rs = $book_rs-&gt;search({
   author =&gt; $author_id,
});</pre>
      <p>Search takes SQL::Abstract formatted queries</p>
      <pre>&gt; perldoc SQL::Abstract</p>
   </div>

   <div class="slide">
      <h1>DBIC: Update</h1>
<pre>$book-&gt;update({
  title =&gt; 'New title',
});</pre>
   </div>

   <div class="slide">
      <h1>DBIC: Delete</h1>
<pre>$book-&gt;delete;</pre>
   </div>

   <div class="slide">
      <h1>Creating models</h1>
   </div>

   <div class="slide">
<pre>package Foo::Schema::Result::Author;
use strict; use warnings;
__PACKAGE__-&gt;table('authors');
__PACKAGE__-&gt;add_columns(
  id =&gt; {
    data_type =&gt; 'int',
    size      =&gt; 8,
  },
  title =&gt; {
    data_type   =&gt; 'varchar',
    is_nullable =&gt; 1,
    size        =&gt; 255,
  },
);
__PACKAGE__-&gt;set_primary_key('id');
__PACKAGE__-&gt;has_many( books =&gt;
   'Foo::Schema::Result::Book', 'author_id'
);
1;
</pre>
   </div>

   <div class="slide">
<pre>package Foo::Schema::Result::Book;
use strict; use warnings;
__PACKAGE__-&gt;table('books');
__PACKAGE__-&gt;add_columns(
  id =&gt; {
    data_type =&gt; 'int',
    size      =&gt; 8,
  },
  name =&gt; {
    data_type   =&gt; 'varchar',
    is_nullable =&gt; 1,
    size        =&gt; 255,
  },
  author_id =&gt; {
    data_type   =&gt; 'int',
    size        =&gt; 8,
    is_nullable =&gt; 1, # &lt;-- probably should be 0
  },
);
__PACKAGE__-&gt;set_primary_key('id');
__PACKAGE__-&gt;belongs_to( author =&gt;
   'Foo::Schema::Result::Author', 'author_id'
);
1;
</pre>
   </div>

   <div class="slide">
      <h1>Schema::Loader</h1>
      <p>DB -&gt; Perl vs Perl -&gt; DB</p>
<pre>package Foo::Schema;
use strict; use warnings;
use base 'DBIx::Class::Schema::Loader';
__PACKAGE__-&gt;loader_options({
   naming =&gt; 'v7',
   debug  =&gt; $ENV{DBIC_TRACE},
});
1;

# elsewhere...

my $schema = Foo::Schema-&gt;connect($dsn, $user, $pass);
</pre>
   </div>

   <div class="slide">
      <h1>Splitting Logic Cleanly</h1>
      <p>Foo::Schema::Result::Bar = individual row</p>
      <p>Foo::Schema::ResultSet::Bar = searches / table </p>
   </div>

   <div class="slide">
      <h1>Using your Schema</h1>
<pre>#!perl
use strict; use warnings;
use lib 'lib';
use Foo::Schema;
my $schema = Foo::Schema-&gt;connect($dns, $user, $pass);
my $author_rs = $schema-&gt;resultset('Author');
my $author    = $author_rs-&gt;create({
   name =&gt; 'Douglas Adams',
});
my $book = $author-&gt;add_to_books({
   title =&gt; '42',
});
</pre>
   </div>

   <div class="slide">
      <h1>DEBUGGING</h1>
      <pre>DBIC_TRACE=1 ./your_script.pl</pre>
   </div>

   <div class="slide">
      <h1>SQL - debugging</h1>
<pre>INSERT INTO authors (name)
   VALUES (?): 'Douglas Adams'

INSERT INTO books (author, title)
   VALUES (?, ?): '5', '42'</pre>
   </div>

   <div class="slide">
      <h1>overloading</h1>
<pre>Foo::Schema::Result::Book
Foo::Schema::ResultSet::Book
Foo::Schema::Result::Author
Foo::Schema::ResultSet::Book</pre>
   </div>

   <div class="slide">
      <h1>Result::</h1>
<pre>package Foo::Schema::Result::Book;
use base 'DBIx::Class::Core';
use strict;
use warnings;

# Result code here

sub isbn {
   my $self = shift;

   # search amazon or something
   my $api = Amazon::API-&gt;book({
      title =&gt; $self-&gt;title
   });

   return $api-&gt;isbn;
}

1;</pre>
   </div>

   <div class="slide">
      <h1>Result::</h1>
<pre>print $book-&gt;isbn;</pre>
   </div>

   <div class="slide">
      <h1>Result:: (inflating)</h1>
<pre>package Foo::Schema::Result::Book;
use base 'DBIx::Class::Core';
use strict;
use warnings;

# Result code here

__PACKAGE__-&gt;load_components('InflateColumn');
use DateTime::Format::MySQL;

__PACKAGE__-&gt;<strong>inflate_column</strong>(
   <strong>date_published</strong> =&gt; {
      inflate =&gt; sub { DateTime::Format::MySQL-&gt;parse_date(shift) },
      deflate =&gt; sub { shift-&gt;ymd},
   },
);
# Automatic see: DBIx::Class::InflateColumn::DateTime</pre>
   </div>

   <div class="slide">
      <h1>Result:: (deflating)</h1>
<pre>$book-&gt;date_published(DateTime-&gt;now);
$book-&gt;update;</pre>
   </div>

   <div class="slide">
      <h1>Result:: (inflating)</h1>
<pre>my $date_published = $book-&gt;date_published;
print $date_published-&gt;month_abbr;</pre>

<strong><em>Nov</em></strong>
   </div>

   <div class="slide">
      <h1>ResultSets::</h1>
<pre>package Foo::Schema::ResultSet::Books;
use base 'DBIx::Class::ResultSet';
sub the_ultimate_books {
   my $self = shift;
   return $self-&gt;search({ title =&gt; { -like =&gt; '%42%' } });
}
sub by_author {
   my ( $self, $author ) = @_;
   return $self-&gt;search({ author =&gt; $author-&gt;id })
}

1;</pre>
   </div>

   <div class="slide">
      <h1>ResultSets::</h1>
<pre>use Foo::Schema;
my $schema = Foo::Schema-&gt;connect(...);
my $book_rs     = Foo::Schema-&gt;resultset('Book');
my $book_search = $book_rs-&gt;the_ultimate_books;
my @books       = $book_search-&gt;all;</pre>
   </div>

   <div class="slide">
      <h1>ResultSets: Chaining</h1>
<pre>
my $book_rs      = $schema-&gt;resultset('Book');
my $author_rs    = $schema-&gt;resultset('Author');
my $author       = $author_model-&gt;search({ name =&gt; 'Douglas Adams' })-&gt;single;
my $book_rs      = $book_model-&gt;the_ultimate_books-&gt;by_author($author);
my @books        = $book_rs-&gt;all;</pre>
   </div>

   <div class="slide">
      <h1>ResultSets: Chaining</h1>
<pre>$book_rs = $schema-&gt;resultset('Book')
  -&gt;the_ultimate_books
  -&gt;by_author($author);</pre>
or

<pre>my $book_rs = $schema-&gt;resultset('Book')
  -&gt;the_ultimate_books;
$book_rs = $book_rs-&gt;by_author($author);</pre>
<pre># Debug (SQL):

# SELECT me.id, me.title, me.date_published, me.author
#   FROM books me
#   WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'
#   WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'</pre>
   </div>

   <div class="slide">
      <h1>ResultSets::chaining</h1>
<pre>my $rs = $book_model
  -&gt;category('childrens')
  -&gt;by_author($author)
  -&gt;published_after('1812')
  -&gt;first_page_contains('once upon')
  -&gt;rating_greater_than(4);

my @books = $rs-&gt;all;</pre>
   </div>

   <div class="slide">
      <h1>overloading before new record</h1>
      <pre>package Foo::Schema::Result::Author;
use base 'DBIx::Class::Core';

sub new {
   my ( $class, $attrs ) = @_;
   # Mess with $attrs
   my $new = $class-&gt;next::method($attrs);
   return $new
}

1;</pre>

   <div class="slide">
      <h1>Relationships</h1>
   </div>

   <div class="slide">
      <h1>Multiple Authors</h1>
   </div>

   <div class="slide">
      <h1>a few relationships</h1>
      (really need picture here)
      (authors -- author_link_to_book -- books)
   </div>

   <div class="slide">
      <h1>Join Table</h1>
<pre>CREATE TABLE author_and_books(
  book_id    int(8),
  author_id  int(8),
  foreign key (book_id)     references books(id),
  foreign key (author_id)   references authors(id)
) engine = InnoDB DEFAULT CHARSET=utf8;

ALTER TABLE `books` DROP `author`;</pre>
   </div>

   <div class="slide">
      <h1>has_many</h1>
   </div>

   <div class="slide">
      <h1>has_many</h1>
<pre>package Foo::Schema::<strong>Result::Book</strong>;

__PACKAGE__-&gt;has_many( author_and_books =&gt;
   'Foo::Schema::Result::Author_Book', 'book_id'
);
   </div>

   <div class="slide">
      <h1>belongs_to</h1>
   </div>

   <div class="slide">
      <h1>belongs_to</h1>
<pre>package Foo::Schema::<strong>Result::Author_Book</strong>;

__PACKAGE__-&gt;belongs_to(
   book =&gt;
   'Foo::Schema::Result::Book', 'book_id'
);
</pre>
   </div>

   <div class="slide">
      <h1>same for Authors</h1>
   </div>

   <div class="slide">
      <h1>many_to_many</h1>
   </div>

   <div class="slide">
      <h1>many_to_many</h1>
      <pre>package Foo::Schema::<strong>Result::Book</strong>;
use base 'DBIx::Class::Core';

__PACKAGE__-&gt;many_to_many(
   authors =&gt; 'author_and_books', 'author'
);

1;
</pre>
   </div>

   <div class="slide">
      <h1>many_to_many</h1>
      <pre>package Foo::Schema::<strong>Result::Book</strong>;
use base 'DBIx::Class::Core';

__PACKAGE__-&gt;many_to_many(
   authors <strong># Accessor name</strong>
   =&gt; "author_and_books", <strong># has_many</strong>
   'author' <strong># foreign relationship name</strong>
);

1;</pre>
   </div>

   <div class="slide">
      <h1>many_to_many</h1>
      <pre>package Foo::Schema::Result::Author;
use base 'DBIx::Class::Core';

__PACKAGE__-&gt;many_to_many(
   "books" <strong># Accessor Name</strong>
   =&gt; "author_and_books", <strong># has_many accessor_name</strong>
   'book' <strong># foreign relationship name</strong>
);

1;
</pre>
   </div>

   <div class="slide">
      <h1>using many_to_many</h1>
      <pre>#!/usr/bin/perl

use Foo::Schema;

my $author_model = Foo::Schema-&gt;resultset('Authors');
my $author       = $author_model-&gt;search({
   name =&gt; 'Douglas Adams',
})-&gt;single;
$author-&gt;add_to_books({
   title =&gt; 'A new book',
});</pre>
   </div>

   <div class="slide">
      <h1>using many_to_many</h1>
      <pre>my $author = $author_model-&gt;search({
   name =&gt; 'Douglas Adams',
})-&gt;single;
<strong>$author-&gt;add_to_books({
   title =&gt; 'A new book',
});</strong>

# SELECT me.id, me.name FROM authors me
#     WHERE ( name = ? ): 'Douglas Adams';
# INSERT INTO books (title) VALUES (?): 'A new book';
# INSERT INTO author_and_books (author, book)
#     VALUES (?, ?): '5', '2';</pre>
   </div>

   <div class="slide">
      <h1>using many_to_many</h1>
      <pre>$author-&gt;add_to_books($book);

$book-&gt;add_to_authors($author_1);
$book-&gt;add_to_authors($author_2);</pre>
   </div>

   <div class="slide">
      <h1>in 16 lines of code</h1>
   </div>

   <div class="slide">
      <h1>errors</h1>
      <p>Read them closely!</p>
   </div>

   <div class="slide">
      <h1>error messages</h1>
      <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>
   </div>

   <div class="slide">
      <h1>error messages</h1>
   <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>
   </div>

   <div class="slide">
      <h1>errors</h1>
      <ul>
         <li>Turn on debugging</li>
         <li>Read error messages (sometimes useful!)</li>
         <li>Check field names</li>
         <li>Check package names</li>
         <li>Check which database you are connected to (dev/test/live?) - repeat above</li>
      </ul>
   </div>

   <div class="slide">
      <h1>bonus slides!</h1>
   </div>

   <div class="slide">
      <h1>Template Toolkit</h1>
      <ul>
         <li><pre>[% author.books.count %]</pre> not working?</li>
         <li>TT all methods are called in list context</li>
         <li><pre>[% author.books<strong>_rs</strong>.count %]</pre> scalar context</li>
         <li><em>Available for all relationships</em></li>
      </ul>
   </div>

   <div class="slide">
      <h1>Catalyst</h1>
      <pre>package Your::App::Model::<strong>Foo</strong>;
use base qw(<strong>Catalyst::Model::Schema::Schema</strong>);

use strict;
use warnings;

__PACKAGE__-&gt;config(
  schema_class =&gt; '<strong>Foo::Schema</strong>',
);

1;</pre>
   <p>Keep your Schema in a <em>separate</em> package to your Catalyst application</p>
   </div>

   <div class="slide">
      <h1>Catalyst</h1>
<pre>sub action_name : Local {
  my ($self, $c) = @_;

  my $model = $c-&gt;model('Schema::Foo');
  my $author_model = $model-&gt;resultset('Authors');

}

1;</pre>
   </div>

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