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Interfaces in Perl5 at The Perl Conference 2019...

Interfaces in Perl5 at The Perl Conference 2019 in Pittsburgh

Kenta Kobayashi

June 17, 2019
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  1. DBI

  2. Goal • To maintain large apps. • Interface is good

    for large apps 1. Easy to fix implementation 2. Stable Dependencies
  3. package TodoRepository; … 
 sub select { my ($self, $user_id)

    = @_; $self->selectall_arrayref( ‘SELECT * FROM todos WHERE user_id = ?’, $user_id ); }
  4. package TodoApp; use TodoRepository; my $repo = TodoRepository->new(…); sub my_todo_list

    {
 my $self = shift; my $todos = $repo->select($self->user_id); return $self->render($todos); }
  5. my $mock = mock TodoRepository => ( select => sub

    { … } ); my $app = TodoApp->new; test $app->my_todo_list;
  6. my $mock = mock TodoRepository => ( select => sub

    { … } ); my $app = TodoApp->new; test $app->my_todo_list; messy to test
  7. package TodoRepository; … sub select { my ($self, $user_id) =

    @_; $self->dbh->selectall_arrayref( ‘SELECT * FROM todos WHERE user_id = ?’, $user_id ); }
  8. package TodoApp; use Moo; has todo_repo => ( is =>

    ‘ro’, does => ‘TodoRepositoryInterface’ );
  9. package TodoApp; … sub my_todo_list {
 my $self = shift;

    my $repo = $self->todo_repo; my $todos = $repo->select($self->user_id); return $self->render($todos); }
  10. package TodoApp; use Moo; has todo_repo => ( is =>

    ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); }
  11. package TodoApp; use Moo; has todo_repo => ( is =>

    ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); }
  12. package TodoApp; use Moo; has todo_repo => ( is =>

    ‘ro’, does => ‘TodoRepositoryInterface’ );
 sub evil_method { $todo_repo->do(“ANY QUERY!!!!”); } Necessary and sufficient features
  13. select($id) # => arrayref of Todo ? # => iterator

    of Todo ? Ambiguous interface input / output
  14. package TodoRepository; use TodoTypes; use Function::Interface::Impl qw( TodoRepositoryInterface ); has

    dbh => ( … ); method select(UserID $user_id) :Return(ArrayRef[Todo]) { … }
  15. package TodoApp; use Moo; use TodoTypes; has todo_repo => (

    isa => ImplOf["TodoRepositoryInterface"], ); sub my_todo_list { … }
  16. sub multi :Return(Num, Str) { 3.14, ‘message' } my ($pi,

    $msg) = multi(); my $count = multi(); # ERROR!
  17. F::P + F::R + F::I F::P + F::R no_check +

    F::I F::P + F::R no_check F::P Case1 Case4 Case2 Case3
  18. F::P + F::R + F::I F::P + F::R no_check +

    F::I F::P + F::R no_check F::P 360653.77/s 1499189.22/s 1499189.22/s 1499189.22/s Case1 Case4 Case2 Case3
  19. Goal • To maintain large apps. • Interface is good

    for large apps 1. Easy to fix implementation 2. Stable Dependencies
  20. Internal • function implementation • Function::Parameters + Function:\:Return • function

    interface • Keyword::Simple + PPR • compare meta infos at compile time
  21. Performance • The same speed as using only F::Parameters •

    Function::Interface::Impl runs at CHECK phase • Function::Return has `no_check` option