Overriding method in multiple DBIx::Class child classes

MattLG has asked for the wisdom of the Perl Monks concerning the following question:

I have a series of DBIx::Class classes that have been auto-generated by the Schema Loader.

I also want to maintain an audit trail of changes to any database table entries, so I've started overriding the update() method on each. But after the first couple, I've realised that the overrides will actually be completely identical.

I'd obviously rather not duplicate 35 lines of identical code in all 20 classes if I can get away with it. What is the best way to achieve this?

               ---------------------
               | DBIx::Class::Core |
               | update()          |
               ---------------------
           /      |            |      \
          /       |            |       \
------------ ------------ ------------ ------------ 
| Table A  | | Table B  | | Table C  | | Table D  | .......
| update() | | update() | | update() | | update() |
------------ ------------ ------------ ------------
[download]

The first option that I considered was multiple inheritance, but the overriding method needs to call its parent method in the DBIx::Class::Core:

sub update {
  my __PACKAGE__ $self = shift;

  # Pre-processing
  :
  :
  :

  # Call the parent method
  $self->next::method(\%new_values);

  # If successful, record audit trail
  :
  :
  :

}
[download]

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Re: Overriding method in multiple DBIx::Class child classes by Your Mother (Archbishop) on Sep 16, 2016 at 16:33 UTC
This should be what you want. A couple of stubs and fake names shown to give you ideas for how to fill in the blanks. :P The new helper component– `package MyDB::Audit; use parent qw( DBIx::Class ); use strict; use warnings; sub update { my $self = shift; return $self->next::method(@_) if some_reason_not_to_log_this_one($self->table); my %data = $self->get_dirty_columns; _log_changed_data(\%data); $self->next::method(@_); } 1;` [download] One of your current result source classes– `package MyDB::Result::Dingus; use strict; use warnings; use parent "DBIx::Class::Core"; __PACKAGE__->load_components("+MyDB::Audit"); __PACKAGE__->table("Dingus"); __PACKAGE__->add_columns( ...et cetera... );` [download] Have fun. :P	[reply] [d/l] [select]
Re^2: Overriding method in multiple DBIx::Class child classes by MattLG (Beadle) on Sep 19, 2016 at 09:45 UTC
Hey, that worked! Thanks! Is that because the update() in MyDB::Audit isn't overriding a parent method in DBIx::Class, so it finds the next appropriate "parent" method?	[reply]
Re^3: Overriding method in multiple DBIx::Class child classes by Your Mother (Archbishop) on Sep 19, 2016 at 12:59 UTC
Yes. Relevant documentation is in MRO::Compat Class::C3, Class::C3::Componentised, and mro. Note that the perl version running the code dictates how this stuff works.	[reply]
Re: Overriding method in multiple DBIx::Class child classes by talexb (Chancellor) on Sep 16, 2016 at 14:16 UTC
Without thinking about this too much, can you just put the logging code in one place, then call it from each of the four methods? Alex / talexb / Toronto Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.	[reply]
Re^2: Overriding method in multiple DBIx::Class child classes by MattLG (Beadle) on Sep 19, 2016 at 09:46 UTC
Yes, that would work. I'd rather do it in a cleaner OO way if possible though.	[reply]
Re: Overriding method in multiple DBIx::Class child classes by trwww (Priest) on Sep 21, 2016 at 19:52 UTC
You're using dbicdump? You can use the additional_base_classes option and put your `update` method in the base class definition. Use `-o additional_base_classes='["MyAppDB::ResultBase"]'` [download] as an argument to dbicdump.	[reply] [d/l] [select]