rename $related_result -> $related_resultset

[chaz/p5-DBIx-Class-ResultSet-RecursiveUpdate] / lib / DBIx / Class / ResultSet / RecursiveUpdate.pm

diff --git a/lib/DBIx/Class/ResultSet/RecursiveUpdate.pm b/lib/DBIx/Class/ResultSet/RecursiveUpdate.pm
index de9ee41ab3b0cee487032b3f2c4bf4ada6010360..04685e7a63fbad39516c80ed236291dd3bc58c21 100644 (file)
--- a/lib/DBIx/Class/ResultSet/RecursiveUpdate.pm
+++ b/lib/DBIx/Class/ResultSet/RecursiveUpdate.pm
@@ -1,174 +1,411 @@
+use strict;
+use warnings;
+

 package DBIx::Class::ResultSet::RecursiveUpdate;
 
 package DBIx::Class::ResultSet::RecursiveUpdate;
 

-use version; $VERSION = qv('0.0.1');
+our $VERSION = '0.013';

 
 

-use warnings;
-use strict;
+use base qw(DBIx::Class::ResultSet);
+
+sub recursive_update {
+    my ( $self, $updates, $fixed_fields ) = @_;
+    return
+        DBIx::Class::ResultSet::RecursiveUpdate::Functions::recursive_update(
+        resultset    => $self,
+        updates      => $updates,
+        fixed_fields => $fixed_fields
+        );
+}
+
+package DBIx::Class::ResultSet::RecursiveUpdate::Functions;

 use Carp;
 use Carp;

+use Scalar::Util qw( blessed );
+
+sub recursive_update {
+    my %params = @_;
+    my ( $self, $updates, $fixed_fields, $object, $resolved,
+        $if_not_submitted )
+        = @params{
+        qw/resultset updates fixed_fields object resolved if_not_submitted/};
+    $resolved ||= {};
+
+    # warn 'entering: ' . $self->result_source->from();
+    carp 'fixed fields needs to be an array ref'
+        if $fixed_fields && ref($fixed_fields) ne 'ARRAY';
+    my %fixed_fields;
+    %fixed_fields = map { $_ => 1 } @$fixed_fields if $fixed_fields;
+    if ( blessed($updates) && $updates->isa('DBIx::Class::Row') ) {
+        return $updates;
+    }
+    if ( $updates->{id} ) {
+        $object = $self->find( $updates->{id}, { key => 'primary' } );
+    }
+    my @missing =
+        grep { !exists $updates->{$_} && !exists $fixed_fields{$_} }
+        $self->result_source->primary_columns;
+    if ( !$object && !scalar @missing ) {

 
 

-use base qw(DBIx::Class::ResultSet);
+        # warn 'finding by: ' . Dumper( $updates ); use Data::Dumper;
+        $object = $self->find( $updates, { key => 'primary' } );
+    }
+    $updates = { %$updates, %$resolved };
+    @missing =
+        grep { !exists $resolved->{$_} } @missing;
+    if ( !$object && !scalar @missing ) {

 
 

-sub recursive_update { 
-    my( $self, $updates ) = @_;
-    my $object;
-    $object = $self->find( $updates, { key => 'primary' } ) || $self->new( {} );
-
-    for my $name ( keys %$updates ){ 
-        if($object->can($name)){
-            my $value = $updates->{$name};
-
-            # updating relations that that should be done before the row is inserted into the database
-            # like belongs_to
-            if( $object->result_source->has_relationship($name) 
-                    and 
-                ref $value
-            ){
-                my $info = $object->result_source->relationship_info( $name );
-                if( $info and not $info->{attrs}{accessor} eq 'multi'
-                        and 
-                    _master_relation_cond( $object, $info->{cond}, _get_pk_for_related( $object, $name ) )
-                ){
-                    my $related_result = $object->related_resultset( $name );
-                    my $sub_object = $related_result->recursive_update( $value );
-                    $object->set_from_related( $name, $sub_object );
-                }
-            }
-            # columns and other accessors
-            elsif( $object->result_source->has_column($name) 
-                    or 
-                !$object->can( 'set_' . $name ) 
-            ) {
-                $object->$name($value);
-            }
+       # warn 'finding by +resolved: ' . Dumper( $updates ); use Data::Dumper;
+        $object = $self->find( $updates, { key => 'primary' } );
+    }
+    $object ||= $self->new( {} );
+
+    # warn Dumper( $updates ); use Data::Dumper;
+    # direct column accessors
+    my %columns;
+
+    # relations that that should be done before the row is inserted into the
+    # database like belongs_to
+    my %pre_updates;
+
+    # relations that that should be done after the row is inserted into the
+    # database like has_many, might_have and has_one
+    my %post_updates;
+    my %other_methods;
+    my %columns_by_accessor = _get_columns_by_accessor($self);
+
+    #    warn 'resolved: ' . Dumper( $resolved );
+    #    warn 'updates: ' . Dumper( $updates ); use Data::Dumper;
+    #    warn 'columns: ' . Dumper( \%columns_by_accessor );
+    for my $name ( keys %$updates ) {
+        my $source = $self->result_source;
+        if ( $columns_by_accessor{$name}
+            && !( $source->has_relationship($name)
+                && ref( $updates->{$name} ) ) )
+        {
+            $columns{$name} = $updates->{$name};
+            next;
+        }
+        if ( !( $source->has_relationship($name) ) ) {
+            $other_methods{$name} = $updates->{$name};
+            next;
+        }
+        my $info = $source->relationship_info($name);
+        if (_master_relation_cond(
+                $source, $info->{cond},
+                _get_pk_for_related( $self, $name )
+            )
+            )
+        {
+            $pre_updates{$name} = $updates->{$name};
+        }
+        else {
+            $post_updates{$name} = $updates->{$name};

         }
         }

-        #warn Dumper($object->{_column_data}); use Data::Dumper;

     }
     }

-    _delete_empty_auto_increment($object);
-    $object->update_or_insert;

 
 

-    # updating relations that can be done only after the row is inserted into the database
-    # like has_many and many_to_many
-    for my $name ( keys %$updates ){
+    # warn 'other: ' . Dumper( \%other_methods ); use Data::Dumper;
+
+    # first update columns and other accessors
+    # so that later related records can be found
+    for my $name ( keys %columns ) {
+        $object->$name( $columns{$name} );
+    }
+    for my $name ( keys %other_methods ) {
+        $object->$name( $updates->{$name} ) if $object->can($name);
+    }
+    for my $name ( keys %pre_updates ) {
+        my $info = $object->result_source->relationship_info($name);
+        _update_relation( $self, $name, $updates->{$name}, $object, $info,
+            $if_not_submitted );
+    }
+
+    # $self->_delete_empty_auto_increment($object);
+    # don't allow insert to recurse to related objects
+    # do the recursion ourselves
+    # $object->{_rel_in_storage} = 1;
+    $object->update_or_insert if $object->is_changed;
+
+    # updating many_to_many
+    for my $name ( keys %$updates ) {
+        next if exists $columns{$name};

         my $value = $updates->{$name};
         my $value = $updates->{$name};

-        # many to many case
-        if($object->can($name) and 
-            !$object->result_source->has_relationship($name) and 
-            $object->can( 'set_' . $name )
-        ) {
-                my ( $pk ) = _get_pk_for_related( $object, $name );
-                my @values = @{$updates->{$name}};
-                my @rows;
-                my $result_source = $object->$name->result_source;
-                @rows = $result_source->resultset->search({ $pk => [ @values ] } ) if @values; 
-                my $set_meth = 'set_' . $name;
-                $object->$set_meth( \@rows );
-        }
-        elsif( $object->result_source->has_relationship($name) ){
-            my $info = $object->result_source->relationship_info( $name );
-            # has many case
-            if( ref $updates->{$name} eq 'ARRAY' ){
-                for my $sub_updates ( @{$updates->{$name}} ) {
-                    my $sub_object = $object->search_related( $name )->recursive_update( $sub_updates );
-                }
+
+        if ( is_m2m( $self, $name ) ) {
+            my ($pk) = _get_pk_for_related( $self, $name );
+            my @rows;
+            my $result_source = $object->$name->result_source;
+            my @updates;
+            if ( !defined $value ) {
+                next;
+            }
+            elsif ( ref $value ) {
+                @updates = @{$value};

             }
             }

-            # might_have and has_one case
-            elsif ( ! _master_relation_cond( $object, $info->{cond}, _get_pk_for_related( $object, $name ) ) ){
-                my $sub_object = $object->search_related( $name )->recursive_update( $value );
-                #$object->set_from_related( $name, $sub_object );
+            else {
+                @updates = ($value);

             }
             }

+            for my $elem (@updates) {
+                if ( ref $elem ) {
+                    push @rows,
+                        recursive_update(
+                        resultset => $result_source->resultset,
+                        updates   => $elem
+                        );
+                }
+                else {
+                    push @rows,
+                        $result_source->resultset->find( { $pk => $elem } );
+                }
+            }
+            my $set_meth = 'set_' . $name;
+            $object->$set_meth( \@rows );

         }
     }
         }
     }

+    for my $name ( keys %post_updates ) {
+        my $info = $object->result_source->relationship_info($name);
+        _update_relation( $self, $name, $updates->{$name}, $object, $info,
+            $if_not_submitted );
+    }

     return $object;
 }
 
     return $object;
 }
 

-sub _delete_empty_auto_increment {
-    my ( $object ) = @_;
-    for my $col ( keys %{$object->{_column_data}}){
-        if( $object->result_source->column_info( $col )->{is_auto_increment} 
-                and 
-            ( ! defined $object->{_column_data}{$col} or $object->{_column_data}{$col} eq '' )
-        ){
-            delete $object->{_column_data}{$col}
+# returns DBIx::Class::ResultSource::column_info as a hash indexed by column accessor || name
+sub _get_columns_by_accessor {
+    my $self   = shift;
+    my $source = $self->result_source;
+    my %columns;
+    for my $name ( $source->columns ) {
+        my $info = $source->column_info($name);
+        $info->{name} = $name;
+        $columns{ $info->{accessor} || $name } = $info;
+    }
+    return %columns;
+}
+
+# Arguments: $name, $updates, $object, $info, $if_not_submitted
+
+sub _update_relation {
+    my ( $self, $name, $updates, $object, $info, $if_not_submitted ) = @_;
+    # get a related resultset without a condition
+    my $related_resultset =
+        $self->related_resultset($name)->result_source->resultset;
+    my $resolved;
+    if ( $self->result_source->can('_resolve_condition') ) {
+        $resolved =
+            $self->result_source->_resolve_condition( $info->{cond}, $name,
+            $object );
+    }
+    else {
+        $resolved =
+            $self->result_source->resolve_condition( $info->{cond}, $name,
+            $object );
+    }
+
+    # warn "$name resolved: " . Dumper( $resolved ); use Data::Dumper;
+    $resolved = {}
+        if defined $DBIx::Class::ResultSource::UNRESOLVABLE_CONDITION
+            && $DBIx::Class::ResultSource::UNRESOLVABLE_CONDITION
+            == $resolved;
+
+    # an arrayref is only valid for has_many rels
+    if ( ref $updates eq 'ARRAY' ) {
+        my @updated_ids;
+        for my $sub_updates ( @{$updates} ) {
+            my $sub_object = recursive_update(
+                resultset => $related_resultset,
+                updates   => $sub_updates,
+                resolved  => $resolved
+            );
+            push @updated_ids, $sub_object->id;
+        }
+        my @related_pks = $related_resultset->result_source->primary_columns;
+        if ( defined $if_not_submitted && $if_not_submitted eq 'delete' ) {
+
+            # only handles related result classes with single primary keys
+            if ( 1 == scalar @related_pks ) {
+                $object->$name->search(
+                    { $related_pks[0] => { -not_in => \@updated_ids } } )
+                    ->delete;
+            }
+        }
+        elsif ( defined $if_not_submitted
+            && $if_not_submitted eq 'set_to_null' )
+        {
+
+            # only handles related result classes with single primary keys
+            if ( 1 == scalar @related_pks ) {
+                my @fk = keys %$resolved;
+                $object->$name->search(
+                    { $related_pks[0] => { -not_in => \@updated_ids } } )
+                    ->update( { $fk[0] => undef } );
+            }

         }
     }
         }
     }

+    else {
+        my $sub_object;
+        if ( ref $updates ) {
+
+            # for might_have relationship
+            if ( $info->{attrs}{accessor} eq 'single'
+                && defined $object->$name )
+            {
+                $sub_object = recursive_update(
+                    resultset => $related_resultset,
+                    updates   => $updates,
+                    object    => $object->$name
+                );
+            }
+            else {
+                $sub_object = recursive_update(
+                    resultset => $related_resultset,
+                    updates   => $updates,
+                    resolved  => $resolved
+                );
+            }
+        }
+        elsif ( !ref $updates ) {
+            $sub_object = $related_resultset->find($updates)
+                unless (
+                !$updates
+                && ( exists $info->{attrs}{join_type}
+                    && $info->{attrs}{join_type} eq 'LEFT' )
+                );
+        }
+        $object->set_from_related( $name, $sub_object )
+            unless (
+               !$sub_object
+            && !$updates
+            && ( exists $info->{attrs}{join_type}
+                && $info->{attrs}{join_type} eq 'LEFT' )
+            );
+    }

 }
 
 }
 

-sub _get_pk_for_related {
-    my ( $object, $relation ) = @_;
+sub is_m2m {
+    my ( $self, $relation ) = @_;
+    my $rclass = $self->result_class;

 
 

-    my $rs = $object->result_source->resultset;
-    my $result_source = _get_related_source( $rs, $relation );
-    return $result_source->primary_columns;
+    # DBIx::Class::IntrospectableM2M
+    if ( $rclass->can('_m2m_metadata') ) {
+        return $rclass->_m2m_metadata->{$relation};
+    }
+    my $object = $self->new( {} );
+    if (    $object->can($relation)
+        and !$self->result_source->has_relationship($relation)
+        and $object->can( 'set_' . $relation ) )
+    {
+        return 1;
+    }
+    return;

 }
 
 }
 

-sub _get_related_source {
-    my ( $rs, $name ) = @_;
-    if( $rs->result_source->has_relationship( $name ) ){
-        return $rs->result_source->related_source( $name );
+sub get_m2m_source {
+    my ( $self, $relation ) = @_;
+    my $rclass = $self->result_class;
+
+    # DBIx::Class::IntrospectableM2M
+    if ( $rclass->can('_m2m_metadata') ) {
+        return $self->result_source->related_source(
+            $rclass->_m2m_metadata->{$relation}{relation} )
+            ->related_source(
+            $rclass->_m2m_metadata->{$relation}{foreign_relation} );

     }
     }

+    my $object = $self->new( {} );
+    my $r = $object->$relation;
+    return $r->result_source;
+}
+
+sub _delete_empty_auto_increment {
+    my ( $self, $object ) = @_;
+    for my $col ( keys %{ $object->{_column_data} } ) {
+        if ($object->result_source->column_info($col)->{is_auto_increment}
+            and ( !defined $object->{_column_data}{$col}
+                or $object->{_column_data}{$col} eq '' )
+            )
+        {
+            delete $object->{_column_data}{$col};
+        }
+    }
+}
+
+sub _get_pk_for_related {
+    my ( $self, $relation ) = @_;
+    my $result_source;
+    if ( $self->result_source->has_relationship($relation) ) {
+        $result_source = $self->result_source->related_source($relation);
+    }
+

     # many to many case
     # many to many case

-    my $row = $rs->new({});
-    if ( $row->can( $name ) and $row->can( 'add_to_' . $name ) and $row->can( 'set_' . $name ) ){
-        my $r = $row->$name;
-        return $r->result_source;
+    if ( is_m2m( $self, $relation ) ) {
+        $result_source = get_m2m_source( $self, $relation );

     }
     }

-    return;
+    return $result_source->primary_columns;

 }
 
 }
 

+# This function determines wheter a relationship should be done before or
+# after the row is inserted into the database
+# relationships before: belongs_to
+# relationships after: has_many, might_have and has_one

 sub _master_relation_cond {
 sub _master_relation_cond {

-    my ( $object, $cond, @foreign_ids ) = @_;
+    my ( $source, $cond, @foreign_ids ) = @_;

     my $foreign_ids_re = join '|', @foreign_ids;
     my $foreign_ids_re = join '|', @foreign_ids;

-    if ( ref $cond eq 'HASH' ){
+    if ( ref $cond eq 'HASH' ) {

         for my $f_key ( keys %{$cond} ) {
         for my $f_key ( keys %{$cond} ) {

+

             # might_have is not master
             my $col = $cond->{$f_key};
             $col =~ s/self\.//;
             # might_have is not master
             my $col = $cond->{$f_key};
             $col =~ s/self\.//;

-            if( $object->column_info( $col )->{is_auto_increment} ){
+            if ( $source->column_info($col)->{is_auto_increment} ) {

                 return 0;
             }
                 return 0;
             }

-            if( $f_key =~ /^foreign\.$foreign_ids_re/ ){
+            if ( $f_key =~ /^foreign\.$foreign_ids_re/ ) {

                 return 1;
             }
         }
                 return 1;
             }
         }

-    }elsif ( ref $cond eq 'ARRAY' ){
-        for my $new_cond ( @$cond ) {
-            return 1 if _master_relation_cond( $object, $new_cond, @foreign_ids );
+    }
+    elsif ( ref $cond eq 'ARRAY' ) {
+        for my $new_cond (@$cond) {
+            return _master_relation_cond( $source, $new_cond, @foreign_ids );

         }
     }
     return;
 }
 
         }
     }
     return;
 }
 

-# Module implementation here
-
-
-1; # Magic true value required at end of module
+1;    # Magic true value required at end of module

 __END__
 
 =head1 NAME
 
 __END__
 
 =head1 NAME
 

-DBIx::Class::ResultSet::RecursiveUpdate - like update_or_create - but recursive 
-
+DBIx::Class::ResultSet::RecursiveUpdate - like update_or_create - but recursive

 
 

-=head1 VERSION
+=head1 SYNOPSIS

 
 

-This document describes DBIx::Class::ResultSet::RecursiveUpdate version 0.0.1
+The functional interface:
+
+    my $new_item = DBIx::Class::ResultSet::RecursiveUpdate::Functions::recursive_update({ 
+        resultset => $schema->resultset( 'Dvd' ),
+        updates => {
+            id => 1, 
+            owned_dvds => [ 
+                { 
+                  title => 'One Flew Over the Cuckoo's Nest' 
+                } 
+            ] 
+        }
+    });

 
 
 
 

-=head1 SYNOPSIS
+As ResultSet subclass:

 
 

-   __PACKAGE__->load_namespaces( default_resultset_class => '+DBIx::Class::ResultSet::RecursiveUpdate' );
+    __PACKAGE__->load_namespaces( default_resultset_class => '+DBIx::Class::ResultSet::RecursiveUpdate' );

 
 in the Schema file (see t/lib/DBSchema.pm).  Or appriopriate 'use base' in the ResultSet classes. 
 
 Then:
 
 
 in the Schema file (see t/lib/DBSchema.pm).  Or appriopriate 'use base' in the ResultSet classes. 
 
 Then:
 

-=for author to fill in:
-

     my $user = $user_rs->recursive_update( { 
         id => 1, 
         owned_dvds => [ 
         { 
     my $user = $user_rs->recursive_update( { 
         id => 1, 
         owned_dvds => [ 
         { 

-          id => undef, 

           title => 'One Flew Over the Cuckoo's Nest' 
         } 
         ] 
           title => 'One Flew Over the Cuckoo's Nest' 
         } 
         ] 


@@ -178,72 +415,222 @@ Then:
   
 =head1 DESCRIPTION
 
   
 =head1 DESCRIPTION
 

-=for author to fill in:
-    You can feed the ->create method with a recursive datastructure and have the related records
-    created.  Unfortunately you cannot do a similar thing with update_or_create - this module
-    tries to fill that void. 
-    It is a base class for ResultSets providing just one method: recursive_update
-    which works just like update_or_create but can recursively update or create
-    data objects composed of multiple rows. All rows need to be identified by primary keys
-    - so you need to provide them in the update structure (unless they can be deduced from 
-    the parent row - for example when you have a belongs_to relationship).  
-    When creating new rows in a table with auto_increment primary keys you need to 
-    put 'undef' for the key value - this is then removed
-    and a correct INSERT statement is generated.  
+This is still experimental. I've added a functional interface so that it can be used 
+in Form Processors and not require modification of the model.

 
 

-    For a many_to_many (pseudo) relation you can supply a list of primary keys
-    from the other table - and it will link the record at hand to those and
-    only those records identified by them.  This is convenient for handling web
-    forms with check boxes (or a SELECT box with multiple choice) that let you
-    update such (pseudo) relations.
+You can feed the ->create method with a recursive datastructure and have the related records
+created.  Unfortunately you cannot do a similar thing with update_or_create - this module
+tries to fill that void. 

 
 

-    For a description how to set up base classes for ResultSets see load_namespaces
-    in DBIx::Class::Schema.
+It is a base class for ResultSets providing just one method: recursive_update
+which works just like update_or_create but can recursively update or create
+data objects composed of multiple rows. All rows need to be identified by primary keys
+- so you need to provide them in the update structure (unless they can be deduced from 
+the parent row - for example when you have a belongs_to relationship).  
+If not all colums comprising the primary key are specified - then a new row will be created,
+with the expectation that the missing columns will be filled by it (as in the case of auto_increment 
+primary keys).  

 
 

-    The support for many to many pseudo relationships should be treated as prototype -
-    the DBIC author disagrees with the way I did it.

 
 

+If the resultset itself stores an assignement for the primary key, 
+like in the case of:
+    
+    my $restricted_rs = $user_rs->search( { id => 1 } );

 
 

-=head1 INTERFACE 
+then you need to inform recursive_update about additional predicate with a second argument:
+
+    my $user = $restricted_rs->recursive_update( { 
+        owned_dvds => [ 
+        { 
+          title => 'One Flew Over the Cuckoo's Nest' 
+        } 
+        ] 
+      },
+      [ 'id' ]
+    );
+
+This will work with a new DBIC release.
+
+For a many_to_many (pseudo) relation you can supply a list of primary keys
+from the other table - and it will link the record at hand to those and
+only those records identified by them.  This is convenient for handling web
+forms with check boxes (or a SELECT box with multiple choice) that let you
+update such (pseudo) relations.  
+
+For a description how to set up base classes for ResultSets see load_namespaces
+in DBIx::Class::Schema.
+
+=head1 DESIGN CHOICES
+
+Columns and relationships which are excluded from the updates hashref aren't
+touched at all.
+
+=head2 Treatment of belongs_to relations
+
+In case the relationship is included but undefined in the updates hashref,
+all columns forming the relationship will be set to null.
+If not all of them are nullable, DBIx::Class will throw an error.
+
+Updating the relationship:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id    => 1,
+        owner => $user->id,
+    });
+
+Clearing the relationship (only works if cols are nullable!):
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id    => 1,
+        owner => undef,
+    });
+
+=head2 Treatment of might_have relationships
+
+In case the relationship is included but undefined in the updates hashref,
+all columns forming the relationship will be set to null.
+
+Updating the relationship:
+
+    my $user = $user_rs->recursive_update( {
+        id => 1,
+        address => {
+            street => "101 Main Street",
+            city   => "Podunk",
+            state  => "New York",
+        }
+    });
+
+Clearing the relationship:
+
+    my $user = $user_rs->recursive_update( {
+        id => 1,
+        address => undef,
+    });
+
+=head2 Treatment of has_many relations
+
+If a relationship key is included in the data structure with a value of undef
+or an empty array, all existing related rows will be deleted, or their foreign
+key columns will be set to null.
+
+The exact behaviour depends on the nullability of the foreign key columns and
+the value of the "if_not_submitted" parameter. The parameter defaults to
+undefined which neither nullifies nor deletes.

 
 

-=for uthor to fill in:
+When the array contains elements they are updated if they exist, created when
+not and deleted if not included.
+
+=head3 All foreign table columns are nullable
+
+In this case recursive_update defaults to nullifying the foreign columns.
+
+=head3 Not all foreign table columns are nullable
+
+In this case recursive_update deletes the foreign rows.
+
+Updating the relationship:
+
+    Passing ids:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id   => 1,
+        tags => [1, 2],
+    });
+
+    Passing hashrefs:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id   => 1,
+        tags => [
+            {
+                id   => 1,
+                file => 'file0'
+            },
+            {
+                id   => 2,
+                file => 'file1',
+            },
+        ],
+    });
+
+    Passing objects:
+
+    TODO
+
+    You can even mix them:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id   => 1,
+        tags => [ '2', { id => '3' } ],
+    });
+
+Clearing the relationship:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id   => 1,
+        tags => undef,
+    });
+
+    This is the same as passing an empty array:
+
+    my $dvd = $dvd_rs->recursive_update( {
+        id   => 1,
+        tags => [],
+    });
+
+=head2 Treatment of many-to-many pseudo relations
+
+The function gets the information about m2m relations from DBIx::Class::IntrospectableM2M.
+If it isn't loaded in the ResultSource classes the code relies on the fact that:
+
+    if($object->can($name) and
+             !$object->result_source->has_relationship($name) and
+             $object->can( 'set_' . $name )
+         )
+
+Then $name must be a many to many pseudo relation.
+And that in a similarly ugly was I find out what is the ResultSource of
+objects from that many to many pseudo relation.
+
+
+=head1 INTERFACE 

 
 =head1 METHODS
 
 =head2 recursive_update
 
 
 =head1 METHODS
 
 =head2 recursive_update
 

-The only method here.
+The method that does the work here.
+
+=head2 is_m2m
+
+$self->is_m2m( 'name ' ) - answers the question if 'name' is a many to many
+(pseudo) relation on $self.
+
+=head2 get_m2m_source
+
+$self->get_m2m_source( 'name' ) - returns the ResultSource linked to by the many
+to many (pseudo) relation 'name' from $self.
+

 
 =head1 DIAGNOSTICS
 
 
 =head1 CONFIGURATION AND ENVIRONMENT
 
 
 =head1 DIAGNOSTICS
 
 
 =head1 CONFIGURATION AND ENVIRONMENT
 

-=for author to fill in:
- 

 DBIx::Class::RecursiveUpdate requires no configuration files or environment variables.
 
 DBIx::Class::RecursiveUpdate requires no configuration files or environment variables.
 

-

 =head1 DEPENDENCIES
 
 =head1 DEPENDENCIES
 

-=for author to fill in:
-

     DBIx::Class
 
     DBIx::Class
 

-None.
-
-

 =head1 INCOMPATIBILITIES
 
 =head1 INCOMPATIBILITIES
 

-=for author to fill in:
-

 None reported.
 
 
 =head1 BUGS AND LIMITATIONS
 
 None reported.
 
 
 =head1 BUGS AND LIMITATIONS
 

-=for author to fill in:
-

 No bugs have been reported.
 
 Please report any bugs or feature requests to
 No bugs have been reported.
 
 Please report any bugs or feature requests to