new tasks

Task/Delegates/Perl/delegates-2.pl

@@ -0,0 +1,54 @@
+use 5.010_000;
+
+package Delegate::Protocol
+use Moose::Role;
+# All methods in the Protocol is optional
+#optional  'thing';
+# If we wanted to have a required method, we would state:
+# requires 'required_method';
+#
+
+package Delegate::NoThing;
+use Moose;
+with 'Delegate::Protocol';
+
+package Delegate;
+use Moose;
+
+#  The we confirm to Delegate::Protocol
+with 'Delegate::Protocol';
+sub thing { 'delegate implementation' };
+
+package Delegator;
+use Moose;
+
+has delegate => (
+     is      => 'rw',
+    does => 'Delegate::Protocol', # Moose insures that the delegate confirms to the protocol.
+   predicate => 'hasDelegate'
+);
+
+sub operation {
+
+    my ($self) = @_;
+    if( $self->hasDelegate  && $self->delegate->can('thing') ){
+        return $self->delegate->thing() . $postfix; # we are know that delegate has thing.
+    } else {
+        return 'default implementation';
+   }
+};
+
+package main;
+use strict;
+
+# No delegate
+my $delegator = Delegator->new();
+$delegator->operation eq 'default implementation' or die;
+
+# With a delegate that does not implement "thing"
+$delegator->delegate(  Delegate::NoThing->new );
+$delegator->operation eq 'default implementation' or die;
+
+# With delegate that implements "thing"
+$delegator->delegate(  Delegate->new );
+$delegator->operation eq 'delegate implementation' or die;