Caleb Cushing's Blog

Moose Interface Pattern with parameter enforcement

Moose interfaces are problematic, for 2 reasons.

  1. They are compile time, but runtime features such as attribute delegation could provide the interface (role ordering is the real problem here)
  2. They don’t ensure anything other than the method name.

I think this problem can be solved better by using around instead of requires

package Interface::Create;
use Moose::Role;
use Type::Params    qw( compile       );
use Types::Standard qw( slurpy HashRef);

around create => sub {
        my $orig = shift;
	my $self = shift;

	state $check = compile( slurpy HashRef );
	my ( $obj_args ) = $check->( @_ );

	return $self->$orig( $obj_args );

Ordering of course still matters here as you can have multiple around modifiers on a method. This will throw an exception if method is missing or if the types passed in are not correct.


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