Turning a row id into an accessor

From ClassDBI

Say you want to store configuration data in a database, such as:

Table: preferences

 +----+------------------+----------------------------+
 | id | name             | value                      |
 +----+------------------+----------------------------+
 |  0 | filename         | /path/to/file.txt          |
 |  1 | item_enabled     | 1                          |
 |  2 | task_name        | something                  |
 +----+------------------+----------------------------+

but instead of doing:

 my $row=DB::Prefs->search({ name => "filename" })->first;
 print $row->value,$/;
 $row->value("/new/path/to/file");

you want to set up accessors to point to the row in the database rather than the column:

 print DB::Prefs->filename,$/;
 DB::Prefs->filename("/new/path/to/file");

which is much easier to use and looks cleaner.

All you have to do is create your Prefs class with an AUTOLOAD function, as below:

 package App::Prefs;
 use base 'App';
 use strict;
 __PACKAGE__->table("preferences");
 __PACKAGE__->columns( ALL => qw/ id name value/ );
 
 sub AUTOLOAD {
   my $self = shift;
   my $newval = shift;
   my $attr = our $AUTOLOAD;
   $attr =~ s/.*:://;
   return if($attr eq "DESTROY");
   my $row = $self->search({ name => "$attr" })->first();
   if(defined($newval)) {
     if(!$row) {
       $row=$self->insert({ name => "$attr" });
     }
     $row->value($newval);
     $row->update();
   }
   return defined($row) ? $row->value : undef;
 }

So calling an accessor with no matching "name" in the preferences table will return "undef", calling an accessor with a parameter will insert that name/value pair into the table, and thereafter calling the accessor will return the correct value for the name matching the accessor.