X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FManual%2FCookbook.pod;h=a0bce5e04a0e4b539427187e916e8a65f6449d2d;hb=9e64dfbf92b14c3dac77cf4ed8a8842114cdbfe5;hp=2552b92f855c5752c3b677c89081986e9209af7d;hpb=c5f36986ee748a32b2c82af4ddec92d6baaae126;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Manual/Cookbook.pod b/lib/DBIx/Class/Manual/Cookbook.pod
index 2552b92..a0bce5e 100644
--- a/lib/DBIx/Class/Manual/Cookbook.pod
+++ b/lib/DBIx/Class/Manual/Cookbook.pod
@@ -12,7 +12,7 @@ When you expect a large number of results, you can ask L<DBIx::Class> for a
 paged resultset, which will fetch only a small number of records at a time:
 
   my $rs = $schema->resultset('Artist')->search(
-    {},
+    undef,
     {
       page => 1,  # page to return (defaults to 1)
       rows => 10, # number of results per page
@@ -24,7 +24,7 @@ paged resultset, which will fetch only a small number of records at a time:
 The C<page> attribute does not have to be specified in your search:
 
   my $rs = $schema->resultset('Artist')->search(
-    {},
+    undef,
     {
       rows => 10,
     }
@@ -76,9 +76,9 @@ When you only want selected columns from a table, you can use C<cols> to
 specify which ones you need:
 
   my $rs = $schema->resultset('Artist')->search(
-    {},
+    undef,
     {
-      cols => [qw/ name /]
+      columns => [qw/ name /]
     }
   );
 
@@ -94,7 +94,7 @@ stored procedure name). You then use C<as> to set the column name you will use
 to access the returned value:
 
   my $rs = $schema->resultset('Artist')->search(
-    {},
+    undef,
     {
       select => [ 'name', { LENGTH => 'name' } ],
       as     => [qw/ name name_length /],
@@ -129,7 +129,7 @@ any of your aliases using either of these:
 =head3 SELECT DISTINCT with multiple columns
 
   my $rs = $schema->resultset('Foo')->search(
-    {},
+    undef,
     {
       select => [
         { distinct => [ $source->columns ] }
@@ -138,10 +138,12 @@ any of your aliases using either of these:
     }
   );
 
+  my $count = $rs->next->get_column('count');
+
 =head3 SELECT COUNT(DISTINCT colname)
 
   my $rs = $schema->resultset('Foo')->search(
-    {},
+    undef,
     {
       select => [
         { count => { distinct => 'colname' } }
@@ -155,7 +157,7 @@ any of your aliases using either of these:
 L<DBIx::Class> supports C<GROUP BY> as follows:
 
   my $rs = $schema->resultset('Artist')->search(
-    {},
+    undef,
     {
       join     => [qw/ cds /],
       select   => [ 'name', { count => 'cds.cdid' } ],
@@ -169,6 +171,57 @@ L<DBIx::Class> supports C<GROUP BY> as follows:
   # LEFT JOIN cd cds ON ( cds.artist = me.artistid )
   # GROUP BY name
 
+=head3 Predefined searches
+
+You can write your own DBIx::Class::ResultSet class by inheriting from it
+and define often used searches as methods:
+
+  package My::DBIC::ResultSet::CD;
+  use strict;
+  use warnings;
+  use base 'DBIx::Class::ResultSet';
+
+  sub search_cds_ordered {
+      my ($self) = @_;
+
+      return $self->search(
+          {},
+          { order_by => 'name DESC' },
+      );
+  }
+
+  1;
+
+To use your resultset, first tell DBIx::Class to create an instance of it
+for you, in your My::DBIC::Schema::CD class:
+
+  __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD');
+
+Then call your new method in your code:
+
+   my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
+
+=head3 Predefined searches without writing a ResultSet class
+
+Alternatively you can automatically generate a DBIx::Class::ResultSet
+class by using the ResultSetManager component and tagging your method
+as ResultSet:
+
+  __PACKAGE__->load_components(qw/ ResultSetManager Core /);
+
+  sub search_cds_ordered : ResultSet {
+      my ($self) = @_;
+      return $self->search(
+          {},
+          { order_by => 'name DESC' },
+      );
+  } 
+
+Then call your method in the same way from your code:
+
+   my $ordered_cds = $schema->resultset('CD')->search_cds_ordered();
+
 =head2 Using joins and prefetch
 
 You can use the C<join> attribute to allow searching on, or sorting your
@@ -260,9 +313,8 @@ L<DBIx::Class> has now prefetched all matching data from the C<artist> table,
 so no additional SQL statements are executed. You now have a much more
 efficient query.
 
-Note that as of L<DBIx::Class> 0.04, C<prefetch> cannot be used with
-C<has_many> relationships. You will get an error along the lines of "No
-accessor for prefetched ..." if you try.
+Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with
+C<has_many> relationships.
 
 Also note that C<prefetch> should only be used when you know you will
 definitely use data from a related table. Pre-fetching related tables when you
@@ -330,7 +382,7 @@ From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship
 deep using the same syntax as a multi-step join:
 
   my $rs = $schema->resultset('Tag')->search(
-    {},
+    undef,
     {
       prefetch => {
         cd => 'artist'
@@ -349,6 +401,35 @@ SQL statements:
   my $tag = $rs->first;
   print $tag->cd->artist->name;
 
+=head2 Using relationships
+
+=head3 Create a new row in a related table
+
+  my $book->create_related('author', { name => 'Fred'});
+
+=head3 Search in a related table
+
+Only searches for books named 'Titanic' by the author in $author.
+
+  my $author->search_related('books', { name => 'Titanic' });
+
+=head3 Delete data in a related table
+
+Deletes only the book named Titanic by the author in $author.
+
+  my $author->delete_related('books', { name => 'Titanic' });
+
+=head3 Ordering a relationship result set
+
+If you always want a relation to be ordered, you can specify this when you 
+create the relationship.
+
+To order C<< $book->pages >> by descending page_number.
+
+  Book->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} );
+
+
+
 =head2 Transactions
 
 As of version 0.04001, there is improved transaction support in
@@ -357,24 +438,22 @@ example of the recommended way to use it:
 
   my $genus = $schema->resultset('Genus')->find(12);
 
+  my $coderef2 = sub {
+    $genus->extinct(1);
+    $genus->update;
+  };
+
   my $coderef1 = sub {
-    my ($schema, $genus, $code) = @_;
     $genus->add_to_species({ name => 'troglodyte' });
     $genus->wings(2);
     $genus->update;
-    $schema->txn_do($code, $genus); # Can have a nested transation
+    $schema->txn_do($coderef2); # Can have a nested transaction
     return $genus->species;
   };
 
-  my $coderef2 = sub {
-    my ($genus) = @_;
-    $genus->extinct(1);
-    $genus->update;
-  };
-
   my $rs;
   eval {
-    $rs = $schema->txn_do($coderef1, $schema, $genus, $coderef2);
+    $rs = $schema->txn_do($coderef1);
   };
 
   if ($@) {                             # Transaction failed
@@ -438,6 +517,13 @@ C<next::method>.
     $class->next::method($attrs);
   }
 
+For more information about C<next::method>, look in the L<Class::C3> 
+documentation. See also L<DBIx::Class::Manual::Component> for more
+ways to write your own base classes to do this.
+
+People looking for ways to do "triggers" with DBIx::Class are probably
+just looking for this.
+
 =head2 Stringification
 
 Employ the standard stringification technique by using the C<overload>
@@ -502,8 +588,8 @@ instead:
                          },
   );
   
-  $translator->parser('DBIx::Class');
-  $translator->producer('DBIx::Class::File');
+  $translator->parser('SQL::Translator::Parser::DBIx::Class');
+  $translator->producer('SQL::Translator::Producer::DBIx::Class::File');
   
   my $output = $translator->translate(@args) or die
           "Error: " . $translator->error;
@@ -511,7 +597,7 @@ instead:
   print $output;
 
 You could use L<Module::Find> to search for all subclasses in the MyDB::*
-namespace, which is currently left as an excercise for the reader.
+namespace, which is currently left as an exercise for the reader.
 
 =head2 Schema versioning
 
@@ -626,8 +712,294 @@ The first sets the quotesymbols. If the quote i "symmetric" as " or '
   
   __PACKAGE__->storage->sql_maker->quote_char('"');
 
-is enough. If the left qoute differs form the right quote, the first 
+is enough. If the left quote differs form the right quote, the first 
 notation should be used. name_sep needs to be set to allow the 
 SQL generator to put the quotes the correct place. 
 
+=head2 Overloading methods
+
+L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of 
+method calls.  You have to use calls to C<next::method> to overload methods.  
+More information on using L<Class::C3> with L<DBIx::Class> can be found in 
+L<DBIx::Class::Manual::Component>.
+
+=head3 Changing one field whenever another changes
+
+For example, say that you have three columns, C<id>, C<number>, and 
+C<squared>.  You would like to make changes to C<number> and have
+C<squared> be automagically set to the value of C<number> squared.
+You can accomplish this by overriding C<store_column>:
+
+  sub store_column {
+    my ( $self, $name, $value ) = @_;
+    if ($name eq 'number') {
+      $self->squared($value * $value);
+    }
+    $self->next::method($name, $value);
+  }
+
+Note that the hard work is done by the call to C<next::method>, which
+redispatches your call to store_column to the superclass(es).
+
+=head3 Automatically creating related objects
+
+You might have a class C<Artist> which has many C<CD>s.  Further, you
+want to create a C<CD> object every time you insert an C<Artist> object.
+You can accomplish this by overriding C<insert> on your objects:
+
+  sub insert {
+    my ( $self, @args ) = @_;
+    $self->next::method(@args);
+    $self->cds->new({})->fill_from_artist($self)->insert;
+    return $self;
+  }
+
+where C<fill_from_artist> is a method you specify in C<CD> which sets
+values in C<CD> based on the data in the C<Artist> object you pass in.
+
+=head2 Debugging DBIx::Class objects with Data::Dumper
+
+L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can
+be hard to find the pertinent data in all the data it can generate.
+Specifically, if one naively tries to use it like so,
+
+  use Data::Dumper;
+
+  my $cd = $schema->resultset('CD')->find(1);
+  print Dumper($cd);
+
+several pages worth of data from the CD object's schema and result source will
+be dumped to the screen. Since usually one is only interested in a few column
+values of the object, this is not very helpful.
+
+Luckily, it is possible to modify the data before L<Data::Dumper> outputs
+it. Simply define a hook that L<Data::Dumper> will call on the object before
+dumping it. For example,
+
+  package My::DB::CD;
+
+  sub _dumper_hook {
+    $_[0] = bless {
+      %{ $_[0] },
+      result_source => undef,
+    }, ref($_[0]);
+  }
+
+  [...]
+
+  use Data::Dumper;
+
+  local $Data::Dumper::Freezer = '_dumper_hook';
+
+  my $cd = $schema->resultset('CD')->find(1);
+  print Dumper($cd);
+         # dumps $cd without its ResultSource
+
+If the structure of your schema is such that there is a common base class for
+all your table classes, simply put a method similar to C<_dumper_hook> in the
+base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper>
+will automagically clean up your data before printing it. See
+L<Data::Dumper/EXAMPLES> for more information.
+
+=head2 Retrieving a row object's Schema
+
+It is possible to get a Schema object from a row object like so,
+
+  my $schema = $cd->result_source->schema;
+  my $artist_rs = $schema->resultset('Artist');
+           # for example
+
+This can be useful when you don't want to pass around a Schema object to every
+method.
+
+=head2 Profiling
+
+When you enable L<DBIx::Class::Storage::DBI>'s debugging it prints the SQL
+executed as well as notifications of query completion and transaction
+begin/commit.  If you'd like to profile the SQL you can subclass the
+L<DBIx::Class::Storage::Statistics> class and write your own profiling
+mechanism:
+
+  package My::Profiler;
+  use strict;
+
+  use base 'DBIx::Class::Storage::Statistics';
+
+  use Time::HiRes qw(time);
+
+  my $start;
+
+  sub query_start {
+    my $self = shift();
+    my $sql = shift();
+    my $params = @_;
+
+    print "Executing $sql: ".join(', ', @params)."\n";
+    $start = time();
+  }
+
+  sub query_end {
+    my $self = shift();
+    my $sql = shift();
+    my @params = @_;
+
+    printf("Execution took %0.4f seconds.\n", time() - $start);
+    $start = undef;
+  }
+
+  1;
+
+You can then install that class as the debugging object:
+
+  __PACKAGE__->storage()->debugobj(new My::Profiler());
+  __PACKAGE__->storage()->debug(1);
+
+A more complicated example might involve storing each execution of SQL in an
+array:
+
+  sub query_end {
+    my $self = shift();
+    my $sql = shift();
+    my @params = @_;
+
+    my $elapsed = time() - $start;
+    push(@{ $calls{$sql} }, {
+        params => \@params,
+        elapsed => $elapsed
+    });
+  }
+
+You could then create average, high and low execution times for an SQL
+statement and dig down to see if certain parameters cause aberrant behavior.
+
+=head2 Getting the value of the primary key for the last database insert
+
+AKA getting last_insert_id
+
+If you are using PK::Auto, this is straightforward:
+
+  my $foo = $rs->create(\%blah);
+  # do more stuff
+  my $id = $foo->id; # foo->my_primary_key_field will also work.
+
+If you are not using autoincrementing primary keys, this will probably
+not work, but then you already know the value of the last primary key anyway.
+
+=head2 Dynamic Sub-classing DBIx::Class proxy classes 
+(AKA multi-class object inflation from one table) 
+ 
+L<DBIx::Class> classes are proxy classes, therefore some different techniques 
+need to be employed for more than basic subclassing.  In this example we have  
+a single user table that carries a boolean bit for admin.  We would like  
+like to give the admin users objects(L<DBIx::Class::Row>) the same methods as  
+a regular user but also special admin only methods.  It doesn't make sense to  
+create two seperate proxy-class files for this.  We would be copying all the  
+user methods into the Admin class.  There is a cleaner way to accomplish this. 
+
+Overriding the C<inflate_results()> method within the User proxy-class gives 
+us the effect we want.  This method is called by L<DBIx::Class::ResultSet> when  
+inflating a result from storage.  So we grab the object being returned, inspect 
+the values we are looking for, bless it if it's an admin object, and then  
+return it.  Running the test file below will confirm this works. 
+ 
+B<Schema Definition> 
+ 
+    package DB::Schema; 
+     
+    use base qw/DBIx::Class::Schema/; 
+ 
+    __PACKAGE__->load_classes(qw/User/); 
+ 
+ 
+B<Proxy-Class definitions> 
+ 
+    package DB::Schema::User; 
+     
+    use strict; 
+    use warnings; 
+    use base qw/DBIx::Class/; 
+     
+    ### Defined what our admin class is for ensure_class_loaded 
+    my $admin_class = __PACKAGE__ . '::Admin'; 
+     
+    __PACKAGE__->load_components(qw/PK::Auto Core/); 
+     
+    __PACKAGE__->table('users'); 
+     
+    __PACKAGE__->add_columns(qw/user_id   email    password  
+                                firstname lastname active 
+                                admin/); 
+     
+    __PACKAGE__->set_primary_key('user_id'); 
+     
+    sub inflate_result { 
+        my $self = shift;  
+        my $ret = $self->next::method(@_); 
+        if( $ret->admin ) {### If this is an admin rebless for extra functions  
+            $self->ensure_class_loaded( $admin_class ); 
+            bless $ret, $admin_class; 
+        } 
+        return $ret; 
+    } 
+     
+    sub hello { 
+        print "I am a regular user.\n"; 
+        return ; 
+    } 
+     
+     
+    package DB::Schema::User::Admin; 
+     
+    use strict; 
+    use warnings; 
+    use base qw/DB::Schema::User/; 
+     
+    sub hello 
+    { 
+        print "I am an admin.\n"; 
+        return; 
+    } 
+     
+    sub do_admin_stuff 
+    { 
+        print "I am doing admin stuff\n"; 
+        return ; 
+    } 
+ 
+B<Test File> test.pl 
+ 
+    use warnings; 
+    use strict; 
+    use DB::Schema; 
+     
+    my $user_data = { email    => 'someguy@place.com',  
+                      password => 'pass1',  
+                      admin    => 0 }; 
+                           
+    my $admin_data = { email    => 'someadmin@adminplace.com',  
+                       password => 'pass2',  
+                       admin    => 1 }; 
+                           
+    my $schema = DB::Schema->connection('dbi:Pg:dbname=test'); 
+     
+    $schema->resultset('User')->create( $user_data ); 
+    $schema->resultset('User')->create( $admin_data ); 
+     
+    ### Now we search for them 
+    my $user = $schema->resultset('User')->single( $user_data ); 
+    my $admin = $schema->resultset('User')->single( $admin_data ); 
+     
+    print ref $user, "\n"; 
+    print ref $admin, "\n"; 
+     
+    print $user->password , "\n"; # pass1 
+    print $admin->password , "\n";# pass2; inherited from User 
+    print $user->hello , "\n";# I am a regular user. 
+    print $admin->hello, "\n";# I am an admin. 
+ 
+    ### The statement below will NOT print 
+    print "I can do admin stuff\n" if $user->can('do_admin_stuff'); 
+    ### The statement below will print 
+    print "I can do admin stuff\n" if $admin->can('do_admin_stuff'); 
+
 =cut