From: Dave Rolsky <autarch@urth.org>
Date: Sat, 6 Feb 2010 03:23:22 +0000 (-0600)
Subject: Fix up trigger instructions and example implementation.
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=ed84c5c65e43867d252f46d13d91df162e6abf6d;p=gitmo%2Fmoose-presentations.git

Fix up trigger instructions and example implementation.

Also ask that people use a native delegation for recording history.
---

diff --git a/moose-class/exercises/answers/06-advanced-attributes/BankAccount.pm b/moose-class/exercises/answers/06-advanced-attributes/BankAccount.pm
index 90c78e2..039fb52 100644
--- a/moose-class/exercises/answers/06-advanced-attributes/BankAccount.pm
+++ b/moose-class/exercises/answers/06-advanced-attributes/BankAccount.pm
@@ -17,9 +17,11 @@ has owner => (
 );
 
 has history => (
+    traits  => ['Array'],
     is      => 'ro',
     isa     => 'ArrayRef[Int]',
     default => sub { [] },
+    handles => { add_history => 'push' },
 );
 
 sub deposit {
@@ -42,9 +44,12 @@ sub withdraw {
 sub _record_balance {
     my $self = shift;
     shift;
+
+    return unless @_;
+
     my $old_value = shift;
 
-    push @{ $self->history }, $old_value;
+    $self->add_history($old_value);
 }
 
 no Moose;
diff --git a/moose-class/exercises/t/06-advanced-attributes.t b/moose-class/exercises/t/06-advanced-attributes.t
index 23ec690..65f11c9 100644
--- a/moose-class/exercises/t/06-advanced-attributes.t
+++ b/moose-class/exercises/t/06-advanced-attributes.t
@@ -10,14 +10,14 @@
 #
 # Copy the deposit and withdraw methods from the HasAccount role.
 #
-# Finally, add a read-only history attribute. This will be an ArrayRef
-# of Int's. This should default to an empty array reference.
+# Finally, add a read-only history attribute. This will be an ArrayRef of
+# Int's. This should default to an empty array reference. Use Native
+# delegation to create a method to push values onto this attribute.
 #
 # Use a trigger to record the _old value_ of the balance each time it
-# changes.
-#
-# Use a BUILD method in BankAccount to record the original balance in
-# the history.
+# changes. This means your trigger should not do anything if it is not passed
+# an old value (this case happens when the attribute is set for the first
+# time).
 #
 # We will now delete the HasAccount role entirely. Instead, add an
 # "account" attribute to Person directly.
diff --git a/moose-class/exercises/t/lib/MooseClass/Tests.pm b/moose-class/exercises/t/lib/MooseClass/Tests.pm
index 4169bd8..0015192 100644
--- a/moose-class/exercises/t/lib/MooseClass/Tests.pm
+++ b/moose-class/exercises/t/lib/MooseClass/Tests.pm
@@ -232,6 +232,14 @@ sub tests06 {
     ok( $ba_meta->has_attribute('balance'),
         'BankAccount class has a balance attribute' );
 
+    my $history_attr = $ba_meta->get_attribute('history');
+
+    ok(
+        $history_attr->meta()
+            ->does_role('Moose::Meta::Attribute::Native::Trait::Array'),
+        'BankAccount history attribute uses native delegation to an array ref'
+    );
+
     ok( $ba_meta->get_attribute('balance')->has_trigger,
         'BankAccount balance attribute has a trigger' );