NAME
    DBIx::MoCo - Light & Fast Model Component

SYNOPSIS
      # First, set up your db.
      package Blog::DataBase;
      use base qw(DBIx::MoCo::DataBase);

      __PACKAGE__->dsn('dbi:mysql:dbname=blog');
      __PACKAGE__->username('test');
      __PACKAGE__->password('test');

      1;

      # Second, create a base class for all models.
      package Blog::MoCo;
      use base qw 'DBIx::MoCo'; # Inherit DBIx::MoCo
      use Blog::DataBase;

      __PACKAGE__->db_object('Blog::DataBase');

      # If you want to use caching feature, you must explicitly set a
      # cache object via cache_object() method.

      use Cache::Memcached;
      my $cache = Cache::Memcached->new;
      $cache->set_servers([ ... ])
      __PACKAGE__->cache_object($cache); # Enables caching by memcached

      1;

      # Third, create your models.
      package Blog::User;
      use base qw 'Blog::MoCo';

      __PACKAGE__->table('user');
      __PACKAGE__->has_many(
          entries => 'Blog::Entry',
          { key => 'user_id' }
      );
      __PACKAGE__->has_many(
          bookmarks => 'Blog::Bookmark',
          { key => 'user_id' }
      );

      1;

      package Blog::Entry;
      use base qw 'Blog::MoCo';

      __PACKAGE__->table('entry');
      __PACKAGE__->has_a(
          user => 'Blog::User',
          { key => 'user_id' }
      );
      __PACKAGE__->has_many(
          bookmarks => 'Blog::Bookmark',
          { key => 'entry_id' }
      );

      1;

      package Blog::Bookmark;
      use base qw 'Blog::MoCo';

      __PACKAGE__->table('bookmark');
      __PACKAGE__->has_a(
          user => 'Blog::User',
          { key => 'user_id' }
      );
      __PACKAGE__->has_a(
          entry => 'Blog::Entry',
          { key => 'entry_id' }
      );

      1;

      # Now, You can use some methods same as Class::DBI.
      # And, all objects are stored in cache automatically.
      my $user = Blog::User->retrieve(user_id => 123);
      print $user->name;
      $user->name('jkontan'); # update db immediately
      print $user->name; # jkontan

      my $user2 = Blog::User->retrieve(user_id => 123);
      # $user is same as $user2

      # You can easily get has_many objects array.
      my $entries = $user->entries;
      my $entries2 = $user->entries;
      # $entries is same reference as $entries2
      my $entry = $entries->first; # isa Blog::Entry
      print $entry->title; # you can use methods in Entry class.

      Blog::Entry->create(
        user_id => 123,
        title => 'new entry!',
      );
      # $user->entries will be flushed automatically.
      my $entries3 = $user->entries;
      # $entries3 isnt $entries

      print ($entries->last eq $entries2->last); # 1
      print ($entries->last eq $entries3->last); # 1
      # same instance

      # You can delay update/create query to database using session.
      DBIx::MoCo->start_session;
      $user->name('jkondo'); # not saved now. changed in cache.
      print $user->name; # 'jkondo'
      $user->save; # update db
      print Blog::User->retrieve(123)->name; # 'jkondo'

      # Or, update queries will be thrown automatically after ending session.
      $user->name('jkontan');
      DBIx::MoCo->end_session;
      print Blog::User->retrieve(123)->name; # 'jkontan'

DESCRIPTION
    Light & Fast Model Component

CLASS DEFINITION METHODS
    Here are common methods related with class definitions.

    add_trigger
        Adds triggers. Here are the types which called from DBIx::MoCo.

          before_create
          after_create
          before_update
          after_update
          before_delete

        You can add your trigger like this.

          package Blog::User;
          __PACKAGE__->add_trigger(before_create => sub
            my ($class, $args) = @_;
            $args->{name} .= '-san';
          });

          # in your scripts
          my $u = Blog::User->create(name => 'ishizaki');
          is ($u->name, 'ishizaki-san'); # ok.

        "before_create" passes a hash reference of new object data as the
        second argument, and all other triggers pass the instance $self.

    has_a
        Defines has_a relationship between 2 models.

    has_many
        Defines has_many relationship between 2 models. You can define
        additional conditions as below.

          Blog::User->has_many(
            root_messages => 'Blog::Message', {
              key => {name => 'to_name'},
              condition => 'reference_id is null',
              order => 'modified desc',
            },
          );

        "condition" is additional sql statement will be used in where
        statement. "order" is used for specifying order statement.

        In above case, SQL statement will be

          SELECT message_id FROM message
          WHERE to_name = 'myname' AND reference_id is null
          ORDER BY modified desc

        And, all each results will be inflated as Blog::Message by
        retrieving all records again (with using cache).

    retrieve_keys
        Defines keys for retrieving by retrieve_all etc.

        If there aren't any unique keys in your table, please specify these
        keys.

          package Blog::Bookmark;

          __PACKAGE__->retrieve_keys(['user_id', 'entry_id']);
          # When user can add multiple bookmarks onto same entry.

    primary_keys
        Returns primary keys. Usually it returns them automatically by
        retrieving schema data from database.

        But you can also redefine this parameter by overriding this method.
        It's useful when MoCo cannot get schema data from your dsn.

          sub primary_keys {['user_id']}

    unique_keys
        Returns unique keys including primary keys. You can override this as
        same as "primary_keys".

          sub unique_keys {['user_id','name']}

    schema
        Returns DBIx::MoCo::Schema object reference related with your model
        class. You can set/get any parameters using Schema's "param" method.
        See DBIx::MoCo::Schema for details.

    columns
        Returns array reference of column names.

    has_column(col_name)
        Returns which the table has the column or not.

    utf8_columns
        Receives array reference and defines utf8 columns.

        When you call utf8 column method, you'll get string with utf8 flag
        on. But you can get raw string when you call param('colname')
        method.

          __PACKAGE__->utf8_columns([qw(title body)]);

          my $e = Blog::Entry->retrieve(1);
          print Encode::is_utf8($e->title); # true
          print Encode::is_utf8($e->param('title')); # false
          print Encode::is_utf8($e->uri); # false

    list_class
        By default, retrieve_all(), search(), etc. return results as a
        DBIx::MoCo::List object when in scalar context. If you want to add
        some features into the list class, you can make a subclass of
        DBIx::MoCo::List and tell your model class to use your own class
        instead by specifying the class via list_class() method.

          # In Blog::Entry
          __PACKAGE__->list_class('Blog::Entry::List');

          # In Blog::Entry::List
          package Blog::Entry::List;
          use base qw/DBIx::MoCo::List/;

          sub to_rss {
              processing rss from entries ...
          }

          1;

          # The return value now has to_rss() method.
          my $entries = Blog::Entry->search( ... ); # is a Blog::Entry::List
          $entries->to_rss;

CACHING FEATURE
  Setup
    If you want to use caching feature provided by DBIx::MoCo, you must
    explicitly set the object via cache_object() method explained below,
    which sets an object to be used when caching data from database. The
    object can be, for example, a Cache::* modules such as Cache::Memory,
    Cache::Memecached, etc.

      # In your Moco.pm
      package Blog::MoCo;
      use base qw 'DBIx::MoCo';

      ...

      use Cache::Memcached;
      my $cache = Cache::Memcached->new;
      $cache->set_servers([ ... ])

      __PACKAGE__->cache_object($cache); # Enables caching by memcached

  Cache Algorithm
    MoCo caches objects effectively.

    There are 3 functions to control MoCo's cache. Their functions are
    called appropriately when some operations are called to a particular
    object.

    Here are the 3 functions.

    store_self_cache
        Stores self instance for all own possible object ids.

    flush_self_cache
        Flushes all caches for all own possible object ids.

    flush_belongs_to
        Flushes all caches whose have has_many arrays including the object.

    And, here are the triggers which call their functions.

    _after_create
        Calls "store_self_cache" and "flush_belongs_to".

    _before_update
        Calls "flush_self_cache".

    _after_update
        Calls "store_self_cache".

    _before_delete
        Calls "flush_self_cache" and "flush_belongs_to".

SESSION & CACHE METHODS
    Here are common methods related with session.

    start_session
        Starts session.

    end_session
        Ends session.

    is_in_session
        Returns DBIx::MoCo is in session or not.

    cache_object
        Sets an object to be used when caching data from database. For
        example, the object can be a Cache::* modules such as Cache::Memory,
        Cache::Memecached, etc.

    cache_status
        Returns cache status of the current session as a hash reference.
        cache_status provides retrieve_count, retrieve_cache_count,
        retrieved_oids retrieve_all_count, has_many_count,
        has_many_cache_count,

    flush
        Delete attribute from given attr. name.

    save
        Saves changed columns in the current session.

    icache_expiration
        Specifies instance cache expiration time in seconds. MoCo store
        has_a, has_many instances in instance variable if this value is set.

          __PACKAGE__->icache_expiration(30);

        It's not necessary to setup icache if you are runnnig MoCo with
        DBIx::MoCo::Cache object because it is more powerful and as fast as
        icache.

        You'd better to consider this option when you are running MoCo with
        centralized cache mechanism such as memcached.

    cache_null_object
        Specifies which MoCo will store null object when retrieve will fail.

    object_id_prefix
        This prefix is used for generating object ids and the ids are used
        as cache keys. Default value of this prefix is the name of class.

        This option is effective when you use some classes which have parent
        -child relationships and they represent same table.

          package Blog::Entry;

          sub object_id_prefix { 'Blog::Entry' }

          1;

          package Blog::Entry::Video;
          use base qw(Blog::Entry);

          1;

        MUID value is used for object_id when the class has muid field even
        if this prefix is specified.

DATA OPERATIONAL METHODS
    Here are common methods related with operating data.

    retrieve
        Retrieves an object and returns that using cache (if possible).

          my $u1 = Blog::User->retrieve(123); # retrieve by primary_key
          my $u2 = Blog::User->retrieve(user_id => 123); # same as above
          my $u3 = Blog::User->retrieve(name => 'jkondo'); # retrieve by name

    restore_from_db
        Restores self attributes from db.

    retrieve_by_db
        Retrieves an object from db.

    retrieve_multi
        Returns results of given array of conditions.

          my $users = Blog::User->retrieve_multi(
            {user_id => 123},
            {user_id => 234},
          );

    retrieve_all
        Returns results of given conditions as "DBIx::MoCo::List" instance.

          my $users = Blog::User->retrieve_all(birthday => '2001-07-15');

    retrieve_or_create
        Retrieves a object or creates new record with given data and returns
        that.

          my $user = Blog::User->retrieve_or_create(name => 'jkondo');

    create
        Creates new object and returns that.

          my $user = Blog::User->create(
            name => 'jkondo',
            birthday => '2001-07-15',
          );

    delete
        Deletes a object. You can call "delete" as both of class and
        instance method.

          $user->delete;
          Blog::User->delete($user);

    delete_all
        Deletes all records with given conditions. You should specify the
        conditions as a hash reference.

          Blog::User->delete_all(where => {birthday => '2001-07-15'});

    search
        Returns results of given conditions as "DBIx::MoCo::List" instance.
        You can specify search conditions in 3 diferrent ways. "Hash
        reference style", "Array reference style" and "Scalar style".

        Hash reference style is same as SQL::Abstract style and like this.

          Blog::User->search(where => {name => 'jkondo'});

        Array style is the most flexible. You can use placeholder.

          Blog::User->search(
            where => ['name = ?', 'jkondo'],
          );
          Blog::User->search(
            where => ['name in (?,?)', 'jkondo', 'cinnamon'],
          );
          Blog::Entry->search(
            where => ['name = :name and date like :date'],
                     name => 'jkondo', date => '2007-04%'],
          );

        Scalar style is the simplest one, and most flexible in other word.

          Blog::Entry->search(
            where => "name = 'jkondo' and DATE_ADD(date, INTERVAL 1 DAY) > NOW()',
          );

        You can also specify "field", "order", "offset", "limit", "group",
        "with" too. Full spec search statement will be like the following.

          Blog::Entry->search(
            field => 'entry_id',
            where => ['name = ?', 'jkondo'],
            order => 'created desc',
            offset => 0,
            limit => 1,
            group => 'title',
            with  => [qw(user)], # for prefetching users related to each entry
          );

        Search results will not be cached because MoCo expects that the
        conditions for "search" will be complicated and should not be
        cached. You should use "retrieve" or "retrieve_all" method instead
        of "search" if you'll use simple conditions.

        See Prefetching section below for details of "with" option in
        "search()" method.

    count
        Returns the count of results matched with given conditions. You can
        specify the conditions in same way as "search"'s where spec.

          Blog::User->count({name => 'jkondo'}); # Hash reference style
          Blog::User->count(['name => ?', 'jkondo']); # Array reference style
          Blog::User->count("name => 'jkondo'"); # Scalar style

    find
        Similar to search, but returns only the first item as a reference
        (not as an array).

    retrieve_by_column(_and_column2)
        Auto generated method which returns an object by using key defined
        is method and given value.

          my $user = Blog::User->retrieve_by_name('jkondo');

    retrieve_by_column(_and_column2)_or_create
        Similar to retrieve_or_create.

          my $user = Blog::User->retrieve_by_name_or_create('jkondo');

    retrieve_by_column_or_column2
        Returns an object matched with given column names.

          my $user = Blog::User->retrieve_by_user_id_or_name('jkondo');

    param
        Set or get attribute from given attr. name.

    set Set attribute which is not related with DB schema or set temporary.

    column_as_something
        Inflate column value by using DBIx::MoCo::Column::* plugins. If you
        set up your plugin like this,

          package DBIx::MoCo::Column::URI;

          sub URI {
            my $self = shift;
            return URI->new($$self);
          }

          sub URI_as_string {
            my $class = shift;
            my $uri = shift or return;
            return $uri->as_string;
          }

          1;

        Then, you can use column_as_URI method as following,

          my $e = MyEntry->retrieve(..);
          print $e->uri; # 'http://test.com/test'
          print $e->uri_as_URI->host; # 'test.com';

          my $uri = URI->new('http://www.test.com/test');
          $e->uri_as_URI($uri); # set uri by using URI instance

        The name of infrate method which will be imported must be same as
        the package name.

        If you don't define "as string" method (such as "URI_as_string"),
        scalar evaluated value of given argument will be used for new value
        instead.

    has_a, has_many auto generated methods
        If you define has_a, has_many relationships,

          package Blog::Entry;
          use base qw 'Blog::MoCo';

          __PACKAGE__->table('entry');
          __PACKAGE__->has_a(
              user => 'Blog::User',
              { key => 'user_id' }
          );
          __PACKAGE__->has_many(
              bookmarks => 'Blog::Bookmark',
              { key => 'entry_id' }
          );

        You can use those keys as methods.

          my $e = Blog::Entry->retrieve(..);
          print $e->user; # isa Blog::User
          print $e->bookmarks; # isa ARRAY of Blog::Bookmark

    quote
        Quotes given string using DBI's quote method.

HINTS FOR PERFORMANCE
  Prefetching
    By default, DBIx::MoCo can issue too many queries in such case as below:

      my $user = Blog::User->retrieve(name => $name);
      for my $entry ( $user->entries ) {
          ## Entry has a user
          $entry->user->name;
      }

    The code above executes more than twice as many queries as the count
    "$user-"entries->size> method returns, which can cause problems on
    performance when the count is large. DBIx::MoCo provides prefetching
    feature to solve the problem.

    You can specify the target to be prefetched by *with* option in model
    class definitions as below:

      package Blog::User;
      use base qw 'Blog::MoCo';

      __PACKAGE__->table('user');
      __PACKAGE__->has_many(
          entries => 'Blog::Entry',
          {
              key  => 'user_id',
              with => [qw(user)],  # Added
          }
      );
      1;

      package Blog::Entry;
      use base qw 'Blog::MoCo';

      __PACKAGE__->table('entry');
      __PACKAGE__->has_a(
          user => 'Blog::User',
          { key => 'user_id' }
      );
      1;

    As a result, "$user-"entry> prefetches users of all entries, and you'll
    see the performance is drastically improved.

      my $user = Blog::User->retrieve(name => $name);
      for my $entry ( $user->entries ) {              # Does prefetching
          ## Entry has a user
          $entry->user->name;
      }

    In case that you temporally don't want the method to prefetch, you can
    inhibit prefetching as below:

      $user->entries({ without => 'user' });

    "with" option described above can appear not only in has_many() method,
    but also in search() method.

      my $entries = Blog::Entry->search(
          ...
          with => [qw(user)],
      );

      for my $entry ( @$entries ) {
          $entry->user->name;       # $entry->user is already prefetched
      }

FORM VALIDATION
    You can validate user parameters using moco's schema. For example you
    can define your validation profile using param like this,

      package Blog::User;

      __PACKAGE__->schema->param([
        name => ['NOT_BLANK', 'ASCII', ['DBIC_UNIQUE', 'Blog::User', 'name']],
        mail => ['NOT_BLANK', 'EMAIL_LOOSE'],
      ]);

    And then,

      # In your scripts
      sub validate {
        my $self = shift;
        my $q = $self->query;
        my $prof = Blog::User->schema->param('validation');
        my $result = FormValidator::Simple->check($q => $prof);
        # handle errors ...
      }

SEE ALSO
    DBIx::MoCo::DataBase, SQL::Abstract, Class::DBI, Cache,

AUTHOR
    Junya Kondo, <jkondo@hatena.com>, Naoya Ito, <platform@hatena.ne.jp>,
    Kentaro Kuribayashi, <kentarok@gmail.com>

COPYRIGHT AND LICENSE
    Copyright (C) Hatena Inc. All Rights Reserved.

    This library is free software; you may redistribute it and/or modify it
    under the same terms as Perl itself.