Data::Object::Signatures

Data-Object Method Signatures

use Data::Object::Signatures;

fun hello (Str $name) {
  return "Hello $name, how are you?";
}

before created() {
  # do something ...
  return $self;
}

after created() {
  # do something ...
  return $self;
}

around updated() {
  # do something ...
  $self->$orig;
  # do something ...
  return $self;
}

This package provides method and function signatures supporting all the type constraints provided by Data::Object::Library.

+=head1 FOREWARNING

Please note that function and method signatures do support parameterized types but with certain caveats. For example, consider the following:

package App::Store;

use Do 'Class', 'App';

method checkout(InstanceOf[Cart] $cart) {
  # perform store checkout
}

1;

This method signature is valid so long as the Cart type is registered in the user-defined App type library. However, in the case where that type is not in the type library, you might be tempted to use the fully-qualified class name, for example:

package App::Store;

use Do 'Class', 'App';

method checkout(InstanceOf[App::Cart] $cart) {
  # perform store checkout
}

1;

Because the type portion of the method signature is evaluated as a Perl string that type declaration is not valid and will result in a syntax error due to the signature parser not expecting the bareword. You might then be tempted to simply quote the fully-qualified class name, for example:

package App::Store;

use Do 'Class', 'App';

method checkout(InstanceOf["App::Cart"] $cart) {
  # perform store checkout
}

1;

TLDR; The signature parser doesn't like that either. To resolve this issue you have two potential solutions, the first being to declare the Cart type in the user-defined library, for example:

package App;

use Do 'Library';

our $Cart = declare 'Cart',
  as InstanceOf["App::Cart"];

package App::Store;

use Do 'Class', 'App';

method checkout(Cart $cart) {
  # perform store checkout
}

1;

Or, alternatively, you could express the type declaration as a string which the parser will except and evaluate properly, for example:

package App::Store;

use Do 'Class';

method checkout(('InstanceOf["App::Cart"]') $cart) {
  # perform store checkout
}

1;