From: Will Hawes <wdhawes@gmail.com>
Date: Sat, 21 Jan 2006 21:06:18 +0000 (+0000)
Subject: add first draft of intro doc for schema-based use
X-Git-Tag: v0.05005~117^2~20
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=8292706e66edd1a95b3af7796aa013285fc842ef;p=dbsrgits%2FDBIx-Class.git
add first draft of intro doc for schema-based use
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diff --git a/lib/DBIx/Class/Manual/SchemaIntro.pod b/lib/DBIx/Class/Manual/SchemaIntro.pod
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+=head1 NAME
+
+DBIx::Class::Manual::SchemaIntro - Introduction to DBIx::Class::Schema
+
+=head1 INTRODUCTION
+
+This document describes how to set up DBIx::Class using the recommended
+schema-based approach.
+
+=head2 Setup
+
+First, you should create your base schema class, which inherits from
+L<DBIx::Class::Schema>:
+
+ package My::Schema;
+ use base qw/DBIx::Class::Schema/;
+
+In this class you load your resultsource ("table", "model") classes, which
+we will define later, using the load_classes() method. You can specify which
+classes to load manually:
+
+ # load My::Schema::Album and My::Schema::Artist
+ __PACKAGE__->load_classes(qw/ Album Artist /);
+
+Or load classes by namespace:
+
+ # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes
+ __PACKAGE__->load_classes(
+ {
+ 'My::Schema' => qw/ Album Artist /,
+ 'My::OtherSchema' => qw/ LinerNotes /
+ }
+ );
+
+Or let your schema class load all classes in its namespace automatically:
+
+ # load My::Schema::*
+ __PACKAGE__->load_classes();
+
+Next, create each of the classes you want to load as specified above:
+
+ package My::Schema::Album;
+ use base qw/DBIx::Class/;
+
+Load any components required by each class with the load_components() method.
+This should consist of "Core" plus any additional components you want to use.
+For example, if you use SQLite and want serial/auto-incrementing primary keys:
+
+ __PACKAGE__->load_components(qw/ PK::Auto::SQLite Core /);
+
+C<PK::Auto> classes exist for many databases; see
+L<DBIx::Class::PK::Auto> for more information.
+
+Set the table for your class:
+
+ __PACKAGE__->table('album');
+
+Add columns to your class:
+
+ __PACKAGE__->add_columns(qw/ albumid artist title /);
+
+Accessors are created for each column automatically, so My::Schema::Album will
+have albumid(), artist() and title() methods.
+
+Define a primary key for your class:
+
+ __PACKAGE__->set_primary_key('albumid');
+
+If you have a multi-column primary key, just pass a list instead:
+
+ __PACKAGE__->set_primary_key( qw/ albumid artistid / );
+
+You can define relationships for any of your classes. L<DBIx::Class> will
+automatically fill in the correct namespace, so if you want to say
+"a My::Schema::Album object belongs to a My::Schema::Artist object" you do not
+need to include the namespace when declaring the relationship:
+
+ __PACKAGE__->belongs_to('artist' => 'Artist');
+
+That's all you need in terms of setup.
+
+=head2 Usage
+
+In your application code, you should first create a connected schema object:
+
+ my $schema = My::Schema->connect( $dsn, $user, $password, $attrs );
+
+You can create as many different schema instances as you need. So if you have
+a second database you want to access:
+
+ my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs );
+
+Note that L<DBIx::Class::Schema> does not cache connnections for you. If you
+use multiple connections, you need to do this manually.
+
+The simplest way to get a record is by primary key:
+
+ my $schema = My::Schema->connect( ... );
+ my $album = $schema->resultset('Album')->find(14);
+
+This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause,
+and return an instance of C<My::Schema::Album> that represents this
+row. Once you have that row, you can access and update columns:
+
+ $album->name('Physical Graffiti');
+ my $title = $album->title; # holds 'Physical Graffiti'
+
+If you prefer, you can use the C<set_column> and C<get_column>
+accessors instead:
+
+ $album->set_column('title', 'Presence');
+ $title = $album->get_column('title');
+
+You use C<update> to commit your changes to the database:
+
+ $album->update();
+
+If needed, you can throw away your local changes like this:
+
+ $album->discard_changes() if $album->is_changed();
+
+As you can see, C<is_changed> allows you to check if there are local
+changes to your object.
+
+=head2 Adding and removing rows
+
+To create a new record in the database, you can use the C<create>
+method. It returns an instance of C<My::Schema::Album> that can be
+used to access the data in the new record:
+
+ my $new_album = $schema->resultset('Album')->create({
+ title => 'Wish You Were Here',
+ artist => 'Pink Floyd'
+ });
+
+Now you can add data to the new record:
+
+ $new_album->label('Capitol');
+ $new_album->year('1975');
+ $new_album->update;
+
+Likewise, you can remove it from the database like this:
+
+ $new_album->delete;
+
+You can also remove records without or retrieving first. This
+operation takes the same kind of arguments as a search.
+
+ # Delete all of Falco's albums
+ $schema->resultset('Album')->delete({ artist => 'Falco' });
+
+=head2 Finding your objects
+
+L<DBIx::Class> provides a few different ways to retrieve data from
+your database. Here's one example:
+
+ # Find all of Santana's albums
+ my $rs = $schema->resultset('Album')->search({ artist => 'Santana' });
+
+In scalar context, as above, C<search> returns a
+L<DBIx::Class::ResultSet> object. It can be used to peek at the first
+album returned by the database:
+
+ my $album = $rs->first;
+ print $album->title;
+
+Or, you can loop over the albums and update each one:
+
+ while (my $album = $rs->next) {
+ print $album->artist . ' - ' . $album->title;
+ $album->year(2001);
+ $album->update;
+ }
+
+For more information on what you can do with a
+L<DBIx::Class::ResultSet>, see L<DBIx::Class::ResultSet/METHODS>.
+
+In list context, the C<search> method returns all of the matching
+rows:
+
+ # Fetch immediately all of Carlos Santana's albums
+ my @albums = @{ $schema->resultset('Album')->search(
+ { artist => 'Carlos Santana' }
+ ) };
+ foreach my $album (@albums) {
+ print $album->artist . ' - ' . $album->title;
+ }
+
+We also provide a handy shortcut for doing a C<LIKE> search:
+
+ # Find albums whose artist starts with 'Jimi'
+ my $rs = MyApp::DB::Album->search_like({ artist => 'Jimi%' });
+
+Or you can provide your own handmade C<WHERE> clause, like:
+
+ # Find Peter Frampton albums from the year 1986
+ my $where = 'artist = ? AND year = ?';
+ my @bind = ( 'Peter Frampton', 1986 );
+ my $rs = $schema->resultset('Album')->search_literal( $where, @bind );
+
+The preferred way to generate complex queries is to provide a
+L<SQL::Abstract> construct to C<search>:
+
+ my $rs = $schema->resultset('Album')->search({
+ artist => { '!=', 'Janis Joplin' },
+ year => { '<' => 1980 },
+ albumid => [ 1, 14, 15, 65, 43 ]
+ });
+
+This results in something like the following C<WHERE> clause:
+
+ WHERE artist != 'Janis Joplin'
+ AND year < 1980
+ AND albumid IN (1, 14, 15, 65, 43)
+
+For more examples of complex queries, see
+L<DBIx::Class::Manual::Cookbook>.
+
+The search can also be modified by passing another hash with
+attributes:
+
+ my @albums = $schema->resultset('Album')->search(
+ { artist => 'Bob Marley' },
+ { rows => 2, order_by => 'year DESC' }
+ );
+
+C<@albums> then holds the two most recent Bob Marley albums.
+
+For a complete overview of the available attributes, see
+L<DBIx::Class::ResultSet/ATTRIBUTES>.
+
+=head1 SEE ALSO
+
+=over 4
+
+=item * L<DBIx::Class::Manual::Cookbook>
+
+=item * L<DBIx::Class::Manual::FAQ>
+
+=back
+
+=cut