name TEXT NOT NULL,
position INTEGER NOT NULL
);
- # Optional: group_id INTEGER NOT NULL
+
+Optionally, add one or more columns to specify groupings, allowing you
+to maintain independent ordered lists within one table:
+
+ CREATE TABLE items (
+ item_id INTEGER PRIMARY KEY AUTOINCREMENT,
+ name TEXT NOT NULL,
+ position INTEGER NOT NULL,
+ group_id INTEGER NOT NULL
+ );
+
+Or even
+
+ CREATE TABLE items (
+ item_id INTEGER PRIMARY KEY AUTOINCREMENT,
+ name TEXT NOT NULL,
+ position INTEGER NOT NULL,
+ group_id INTEGER NOT NULL,
+ other_group_id INTEGER NOT NULL
+ );
In your Schema or DB class add Ordered to the top
of the component list.
package My::Item;
__PACKAGE__->position_column('position');
- __PACKAGE__->grouping_column('group_id'); # optional
+
+If you are using one grouping column, specify it as follows:
+
+ __PACKAGE__->grouping_column('group_id');
+
+Or if you have multiple grouping columns:
+
+ __PACKAGE__->grouping_column(['group_id', 'other_group_id']);
Thats it, now you can change the position of your objects.
$item->move_first();
$item->move_last();
$item->move_to( $position );
+ $item->move_to_group( 'groupname' );
+ $item->move_to_group( 'groupname', $position );
+ $item->move_to_group( {group_id=>'groupname', 'other_group_id=>'othergroupname'} );
+ $item->move_to_group( {group_id=>'groupname', 'other_group_id=>'othergroupname'}, $position );
=head1 DESCRIPTION
sub first_sibling {
my( $self ) = @_;
return 0 if ($self->get_column($self->position_column())==1);
+
return ($self->result_source->resultset->search(
{
$self->position_column => 1,
my $from_position = $self->get_column( $position_column );
return 0 if ( $to_position < 1 );
return 0 if ( $from_position==$to_position );
+ my @between = (
+ ( $from_position < $to_position )
+ ? ( $from_position+1, $to_position )
+ : ( $to_position, $from_position-1 )
+ );
my $rs = $self->result_source->resultset->search({
- -and => [
- $position_column => { ($from_position>$to_position?'<':'>') => $from_position },
- $position_column => { ($from_position>$to_position?'>=':'<=') => $to_position },
- ],
+ $position_column => { -between => [ @between ] },
$self->_grouping_clause(),
});
my $op = ($from_position>$to_position) ? '+' : '-';
- $rs->update({
- $position_column => \"$position_column $op 1",
- });
- $self->set_column( $position_column => $to_position );
- $self->update();
+ $rs->update({ $position_column => \"$position_column $op 1" }); #" Sorry, GEdit bug
+ $self->{_ORDERED_INTERNAL_UPDATE} = 1;
+ $self->update({ $position_column => $to_position });
+ return 1;
+}
+
+
+
+=head2 move_to_group
+
+ $item->move_to_group( $group, $position );
+
+Moves the object to the specified position of the specified
+group, or to the end of the group if $position is undef.
+1 is returned on success, and 0 is returned if the object is
+already at the specified position of the specified group.
+
+$group may be specified as a single scalar if only one
+grouping column is in use, or as a hashref of column => value pairs
+if multiple grouping columns are in use.
+
+=cut
+
+sub move_to_group {
+ my( $self, $to_group, $to_position ) = @_;
+
+ # if we're given a string, turn it into a hashref
+ unless (ref $to_group eq 'HASH') {
+ $to_group = {($self->_grouping_columns)[0] => $to_group};
+ }
+
+ my $position_column = $self->position_column;
+ #my @grouping_columns = $self->_grouping_columns;
+
+ return 0 if ( ! defined($to_group) );
+ return 0 if ( defined($to_position) and $to_position < 1 );
+ return 0 if ( $self->_is_in_group($to_group)
+ and ((not defined($to_position))
+ or (defined($to_position) and $self->$position_column==$to_position)
+ )
+ );
+
+ # Move to end of current group and adjust siblings
+ $self->move_last;
+
+ $self->set_columns($to_group);
+ my $new_group_count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
+ if (!defined($to_position) or $to_position > $new_group_count) {
+ $self->{_ORDERED_INTERNAL_UPDATE} = 1;
+ $self->update({ $position_column => $new_group_count + 1 });
+ }
+ else {
+ my @between = ($to_position, $new_group_count);
+
+ my $rs = $self->result_source->resultset->search({
+ $position_column => { -between => [ @between ] },
+ $self->_grouping_clause(),
+ });
+ $rs->update({ $position_column => \"$position_column + 1" }); #"
+ $self->{_ORDERED_INTERNAL_UPDATE} = 1;
+ $self->update({ $position_column => $to_position });
+ }
+
return 1;
}
return $self->next::method( @_ );
}
+=head2 update
+
+Overrides the DBIC update() method by checking for a change
+to the position and/or group columns. Movement within a
+group or to another group is handled by repositioning
+the appropriate siblings. Position defaults to the end
+of a new group if it has been changed to undef.
+
+=cut
+
+sub update {
+ my $self = shift;
+
+ if ($self->{_ORDERED_INTERNAL_UPDATE}) {
+ delete $self->{_ORDERED_INTERNAL_UPDATE};
+ return $self->next::method( @_ );
+ }
+
+ $self->set_columns($_[0]) if @_ > 0;
+ my %changes = $self->get_dirty_columns;
+ $self->discard_changes;
+
+ my $pos_col = $self->position_column;
+
+ # if any of our grouping columns have been changed
+ if (grep {$_} map {exists $changes{$_}} $self->_grouping_columns ) {
+
+ # create new_group by taking the current group and inserting changes
+ my $new_group = {$self->_grouping_clause};
+ foreach my $col (keys %$new_group) {
+ if (exists $changes{$col}) {
+ $new_group->{$col} = $changes{$col};
+ delete $changes{$col}; # don't want to pass this on to next::method
+ }
+ }
+
+ $self->move_to_group(
+ $new_group,
+ exists($changes{$pos_col}) ? delete($changes{$pos_col}) : $self->$pos_col
+ );
+ }
+ elsif (exists $changes{$pos_col}) {
+ $self->move_to(delete $changes{$pos_col});
+ }
+ return $self->next::method( \%changes );
+}
+
=head2 delete
Overrides the DBIC delete() method by first moving the object
=head2 _grouping_clause
-This method returns a name=>value pare for limiting a search
-by the collection column. If the collection column is not
+This method returns one or more name=>value pairs for limiting a search
+by the grouping column(s). If the grouping column is not
defined then this will return an empty list.
=cut
-
sub _grouping_clause {
my( $self ) = @_;
+ return map { $_ => $self->get_column($_) } $self->_grouping_columns();
+}
+
+
+
+=head2 _get_grouping_columns
+
+Returns a list of the column names used for grouping, regardless of whether
+they were specified as an arrayref or a single string, and returns ()
+if there is no grouping.
+
+=cut
+sub _grouping_columns {
+ my( $self ) = @_;
my $col = $self->grouping_column();
- if ($col) {
- return ( $col => $self->get_column($col) );
+ if (ref $col eq 'ARRAY') {
+ return @$col;
+ } elsif ($col) {
+ return ( $col );
+ } else {
+ return ();
+ }
+}
+
+
+
+=head2 _is_in_group($other)
+
+ $item->_is_in_group( {user => 'fred', list => 'work'} )
+
+Returns true if the object is in the group represented by hashref $other
+=cut
+sub _is_in_group {
+ my ($self, $other) = @_;
+ my $current = {$self->_grouping_clause};
+ return 0 unless (ref $other eq 'HASH') and (keys %$current == keys %$other);
+ for my $key (keys %$current) {
+ return 0 unless exists $other->{$key};
+ return 0 if $current->{$key} ne $other->{$key};
}
- return ();
+ return 1;
}
+
1;
__END__
=head1 BUGS
+=head2 Unique Constraints
+
+Unique indexes and constraints on the position column are not
+supported at this time. It would be make sense to support them,
+but there are some unexpected database issues that make this
+hard to do. The main problem from the author's view is that
+SQLite (the DB engine that we use for testing) does not support
+ORDER BY on updates.
+
=head2 Race Condition on Insert
If a position is not specified for an insert than a position
the position of the other object will not reflect their new value
until you reload them from the database.
-The are times when you will want to move objects as groups, such
+There are times when you will want to move objects as groups, such
as changeing the parent of several objects at once - this directly
conflicts with this problem. One solution is for us to write a
ResultSet class that supports a parent() method, for example. Another