The document discusses how the author evolved the Perlanet software by refactoring it to use Moose and a trait-based architecture. Some key points: - Perlanet started as a monolithic module but was hard to customize or add new features to. - The author used Moose to "slash and burn" the code into a more object-oriented and overridable structure using traits instead of large subclasses. - Traits were used to extract specific behaviors like HTML scrubbing, YAML configuration, etc. into reusable modules. - This allowed Perlanet to become a "hollow shell" that loads functionality via traits, making it easier to customize and extend. - The

1. Evolving Software with Moose

2. Dave Cross [email_address] @davorg

3. Perlanet

4. Perl + Planet

5. Web Feed Aggregation

6. Input: Lots of web feeds

7. Output: Web page + web feed

11. Scratching an itch

12. Wrote it for me

13. CPAN

14. github

15. A few bug fixes

16. A few enhancements

17. Perl Ironman

18. Using Plagger

19. Wanted to use Perlanet

20. Didn't scale well

21. YAML config

22. NWE.pm Hackday

23. Enter the Moose

24. Slash and burn

25. More easily subclassable

26. Monolithic vs Overridable

27. HTML::Scrubber

28. # deep in the 'run' subroutine my %scrub_rules = ( # stuff ); my %scrub_def = ( # more stuff ) my $scrub = HTML::Scrubber->new; $scrub->rules(%scrub_rules); $scrub->default(1, \%scrub_def);

29. Overriding this is hard

30. has 'scrubber' => ( is => 'rw', lazy_build => 1 ); sub _build_scrubber { my $self = shift; # all that previous stuff return $scrub; }

31. Overriding this is easy

32. Repeat half a dozen times

33. YAML config

34. YAML config

35. DB config

36. Better scaling

37. Phase 1 complete

38. Almost

39. Need better tests

40. Release early Release often

41. Phase 2

42. Traits

43. Moose has traits and roles

44. Difference is subtle

45. Implementation looks similar

46. I didn't know the difference

47. Role is like an interface

48. Defines methods that class MUST implement

49. package ARole; use Moose::Role; requires 'do_stuff'; 1;

50. package AClass; use Moose; with 'ARole'; has name => ( is => 'rw', isa => 'Str', ); 1;

51. #!/usr/bin/perl use strict; use warnings; use AClass; my $obj = Aclass->new({ name => 'davorg', });

52. $ ./role_demo 'ARole' requires the method 'do_stuff' to be implemented by 'AClass' ... other scary stuff ...

53. Need to implement method

54. package AClass; use Moose; with 'ARole'; has name => ( is => 'rw', isa => 'Str', ); sub do_stuff { my $self = shift; print $self->name, “ does stuff\n”; } 1;

55. Roles impose an interface

56. (We don't use those in Perlanet)

57. Traits add functionality

58. Like a mixin

59. Remember HTML::Scrubber?

60. package Perlanet::Trait::Scrubber; use Moose::Role; # yes really – hold that thought use HTML::Scrubber; has scrubber => ( is => 'rw', lazy_build => 1, ); sub _build_scrubber { # all that stuff from before return $scrub; }

61. package Perlanet::Trait::Scrubber; use Moose::Role; # yes really – hold that thought use HTML::Scrubber; has scrubber => ( is => 'rw', lazy_build => 1, ); sub _build_scrubber { # all that stuff from before return $scrub; }

62. around 'clean_html' => sub { my $orig = shift; my ($self, $html) = @_; $html = $self->orig($html); $self->scrubber->scrub($html); return $html; } 1;

63. Perlanet.pm has clean_html method

64. But it does nothing until traits are added

65. Perlanet is now a hollow shell of a module

66. All the fun stuff is in traits

67. Perlanet::Simple

68. package Perlanet::Simple; use Moose; extends 'Perlanet'; with qw( Perlanet::Trait::Cache Perlanet::Trait::OPML Perlanet::Trait::Scrubber Perlanet::Trait::Tidy Perlanet::Trait::YAMLConfig Perlanet::Trait::TemplateToolkit Perlanet::Trait::FeedFile );

69. Moose::Role

70. Used in both roles and traits

71. This is Perl

72. Difference is not clear-cut

73. Roles and traits are the same thing

74. Depends where the code is

75. All based on Moose::Role

76. Perlanet now trait-based

77. Easy to add functionality

78. Perlanet trait ecosystem

79. And I learned about Moose roles and traits

80. (And now, so have you)

81. ht tp://search.cpan.org/dist/Perlanet http://theplanetarium.org/ ht tp://perlanet.mag-sol.com/ http://moose.perl.org/