Class::DBI keys as accessors

[duncs]

Category:

Database Programming

Description:

When using Class::DBI with a table such as:

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

you want to use:

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

instead of:

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

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