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Interfaces in Perl5
kobaken a.k.a @kfly8
The Perl Conference 2019 #TPCiP
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me
• kobaken a.k.a @kfly8
• leader Gotanda.pm
• orgnize YAPC::Tokyo 2019
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I ❤
Perl
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Interfaces in Perl5
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DBI
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my $dbh = DBI->connect(...);
my $items = $dbh->selectrow_arrayref(…);
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Unified Interface
independent of datastore
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Unified Interface
provides values
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Limitation makes value
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Agenda
1.DEMO & Features
2.Goal
3.Example: TODO app
4.Internal
5.Performance
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Function::Interface is
Java-like interface
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DEMO
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Features of Function::Interface
1.Typed interface definition
2.Check at compile time
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What is Goal ?
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To maintain large Perl apps
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Interface is good
for large apps
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1. Be easier to fix
implementation
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2. Stable dependencies
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Goal
• To maintain large apps.
• Interface is good for large apps
1. Easy to fix implementation
2. Stable Dependencies
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Example: TODO app
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Case:
“Inheritance”
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package TodoRepository;
use parent qw(DBI);
sub new {
my $class = shift;
$class->connect(…);
}
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package TodoRepository;
…
sub select {
my ($self, $user_id) = @_;
$self->selectall_arrayref(
‘SELECT * FROM todos WHERE user_id = ?’,
$user_id
);
}
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package TodoApp;
use TodoRepository;
my $repo = TodoRepository->new;
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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);
}
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TodoApp
TodoRepository
DBI
TODO table
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TodoApp
TodoRepository
DBI
TODO table
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TodoApp
TodoRepository
DBI
TODO table
Unstable Dependencies
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package TodoApp;
use TodoRepository;
my $repo = TodoRepository->new;
sub evil_method {
$repo->do(“ANY QUERY!!!!”);
}
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package TodoApp;
use TodoRepository;
my $repo = TodoRepository->new;
sub evil_method {
$repo->do(“ANY QUERY!!!!”);
}
Too many features
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easy to test?
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my $mock = mock TodoRepository => (
select => sub { … }
);
my $app = TodoApp->new;
test $app->my_todo_list;
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my $mock = mock TodoRepository => (
select => sub { … }
);
my $app = TodoApp->new;
test $app->my_todo_list;
messy to test
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Problems of “Inheritance” case
1.Unstable dependencies
2.Too many features
3.messy to test
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“Role” case
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package TodoRepositoryInterface;
use Moo::Role;
requires qw(select);
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package TodoRepository;
use Moo;
with qw(
TodoRepositoryInterface
);
has dbh => ( isa => ‘DBI::db’ );
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package TodoRepository;
use Moo;
with qw(
TodoRepositoryInterface
);
has dbh => ( isa => ‘DBI::db’ );
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package TodoRepository;
…
sub select {
my ($self, $user_id) = @_;
$self->dbh->selectall_arrayref(
‘SELECT * FROM todos WHERE user_id = ?’,
$user_id
);
}
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package TodoApp;
use Moo;
has todo_repo => (
is => ‘ro’,
does => ‘TodoRepositoryInterface’
);
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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);
}
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TodoApp
TodoRepository
DBI
TODO table
TodoRepositoryInterface
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TodoApp
TodoRepository
DBI
TODO table
TodoRepositoryInterface
NOT!
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TodoApp
TodoRepository
DBI
TODO table
TodoRepositoryInterface
more stable
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Problems of “Inheritance” case
1.Unstable dependencies
2.Too many features
3.messy to test
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package TodoApp;
use Moo;
has todo_repo => (
is => ‘ro’,
does => ‘TodoRepositoryInterface’
);
sub evil_method {
$todo_repo->do(“ANY QUERY!!!!”);
}
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package TodoApp;
use Moo;
has todo_repo => (
is => ‘ro’,
does => ‘TodoRepositoryInterface’
);
sub evil_method {
$todo_repo->do(“ANY QUERY!!!!”);
}
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package TodoApp;
use Moo;
has todo_repo => (
is => ‘ro’,
does => ‘TodoRepositoryInterface’
);
sub evil_method {
$todo_repo->do(“ANY QUERY!!!!”);
}
Necessary and sufficient features
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Problems of “Inheritance” case
1.Unstable dependencies
2.Too many features
3.messy to test
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easy to test?
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package TestTodoRepository;
use Moo;
with qw(
TodoRepositoryInterface
);
sub select { … }
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package TestTodoRepository;
use Moo;
with qw(
TodoRepositoryInterface
);
sub select { … }
Be easier to test
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Problems of “Inheritance” case
1.Unstable dependencies
2.Too many features
3.messy to test
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no problem at all?
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package TodoRepositoryInterface;
use Moo::Role;
requires qw(select);
sub surprised_method {
.. do anything
}
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package TodoRepositoryInterface;
use Moo::Role;
requires qw(select);
sub surprised_method {
.. do anything
}
Implementation reusable
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package TodoRepositoryInterface;
use Moo::Role;
requires qw(select);
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select($id) ?
select(id => $id) ?
select({ id => $id }) ?
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select($id)
# => arrayref of Todo ?
# => iterator of Todo ?
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select($id)
# => arrayref of Todo ?
# => iterator of Todo ?
Ambiguous interface input / output
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Problems of “Role” case
1.Implementation reusable
2.Ambiguous interface input / output
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“Function::Interface” case
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package TodoRepositoryInterface;
use Function::Interface;
use TodoTypes;
method select(UserID $user_id)
:Return(ArrayRef[Todo]);
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Problems of “Role” case
1.Implementation reusable
2.Ambiguous interface input / output
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package TodoRepositoryInterface;
use Function::Interface;
use TodoTypes;
method select(UserID $user_id)
:Return(ArrayRef[Todo]);
sub surprising_method {
… do anything
}
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package TodoRepositoryInterface;
use Function::Interface;
use TodoTypes;
method select(UserID $user_id)
:Return(ArrayRef[Todo]);
sub surprising_method {
… do anything
}
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Problems of “Role” case
1.Implementation reusable
2.Ambiguous interface input / output
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package TodoRepository;
use TodoTypes;
use Function::Interface::Impl qw(
TodoRepositoryInterface
);
has dbh => ( … );
method select(UserID $user_id)
:Return(ArrayRef[Todo]) {
…
}
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package TodoApp;
use Moo;
use TodoTypes;
has todo_repo => (
isa => ImplOf["TodoRepositoryInterface"],
);
sub my_todo_list { … }
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Looks Good!
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Internal
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requirements
1.function implementation
2.function interface
3.check if interface is implmented
4.interface type
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1. function implementation
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Function::Parameters
• subroutine signatures
• developed by MAUKE
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use Function::Parameters;
use Types::Standard -types;
fun add(Int $a, Int $b) {
return $a + $b
}
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my $info = Function::Parameters::info(\&add);
$info->positional_required;
# => Int $a,
Int $b
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Function::Return
• specify function return types
• created by myself
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sub add :Return(Int) { 3.14 }
add(); # ERROR! Invalid type
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my $info = Function::Return::info(\&add);
$info->types;
# => Int
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Appendix about
Function::Return
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sub multi :Return(Num, Str) {
3.14, ‘message'
}
my ($pi, $msg) = multi();
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sub multi :Return(Num, Str) {
3.14, ‘message'
}
my ($pi, $msg) = multi();
my $count = multi(); # ERROR!
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requirements
1.function implementation
2.function interface
3.check if interface is implemented
4.interface type
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2. function interface
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Function::Interface
• Keyword::Simple
• PPR
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Deparse
fun hello() :Return(Str);
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sub BEGIN {
Function::Interface::_register_info({
package => ‘HelloInterface',
keyword => ‘fun',
subname => ‘message',
params => [],
return => [&Str()]}
);
}
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my $info =
Function::Interface::info(“HelloInterface”);
$info->functions;
# => hello(Str $msg) :Return(Str)
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requirements
1.function implementation
2.function interface
3.check if interface is implemented
4.interface type
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3.check if interface is
implemented
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use Function::Interface::Impl qw(
FooInterface
BarInterface
BazInterface
);
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F::Parameters#info
F::Return#info
F::Interface#info
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F::Parameters#info
F::Return#info
F::Interface#info
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requirements
1.function implementation
2.function interface
3.check if interface is implemented
4.interface type
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use Function::Interface::Types;
my $type = ImplOF[‘FooInterface’];
# Foo is implements of FooInterface
my $foo = Foo->new;
$type->check($foo);
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requirements
1.function implementation
2.function interface
3.check if interface is implemented
4.interface type
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Performance
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F::I::Impl runs
at compile time
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F::Return has
`no_check` option
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Let’s benchmark
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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
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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
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$BTF $BTF $BTF $BTF
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Conclusion
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Features of F::Interface
1.Typed interface definition
2.Check at compile time
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Goal
• To maintain large apps.
• Interface is good for large apps
1. Easy to fix implementation
2. Stable Dependencies
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Internal
• function implementation
• Function::Parameters + Function:\:Return
• function interface
• Keyword::Simple + PPR
• compare meta infos at compile time
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Performance
• The same speed as using only F::Parameters
• Function::Interface::Impl runs at CHECK phase
• Function::Return has `no_check` option
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Questions?
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Thank you!