the canonical repository is now https://github.com/moose/MooseX-UndefTolerant

[gitmo/MooseX-UndefTolerant.git] / lib / MooseX / UndefTolerant / Attribute.pm

diff --git a/lib/MooseX/UndefTolerant/Attribute.pm b/lib/MooseX/UndefTolerant/Attribute.pm
index e1aee78..644611e 100644 (file)
--- a/lib/MooseX/UndefTolerant/Attribute.pm
+++ b/lib/MooseX/UndefTolerant/Attribute.pm
@@ -1,15 +1,60 @@
 package MooseX::UndefTolerant::Attribute;
 use Moose::Role;
 
-around('initialize_instance_slot', sub{
+around('initialize_instance_slot', sub {
     my $orig = shift;
     my $self = shift;
+    my ($meta_instance, $instance, $params) = @_;
 
-    # If the parameter passed in was undef, quietly do nothing but return
-    return unless defined($_->[2]);
+    my $key_name = $self->init_arg;
 
-    # If it was defined, call the real init slot method
+    # If our parameter passed in was undef, remove it from the parameter list...
+    # but leave the value unscathed if the attribute's type constraint can
+    # handle undef (or doesn't have one, which implicitly means it can)
+    if (defined $key_name and not defined($params->{$key_name}))
+    {
+        my $type_constraint = $self->type_constraint;
+        if ($type_constraint and not $type_constraint->check(undef))
+        {
+            delete $params->{$key_name};
+        }
+    }
+
+    # Invoke the real init, as the above line cleared the undef param value
     $self->$orig(@_)
 });
 
-1;
\ No newline at end of file
+1;
+
+# ABSTRACT: Make your attribute(s) tolerant to undef intitialization
+
+__END__
+
+=head1 SYNOPSIS
+
+  package My:Class;
+  use Moose;
+
+  use MooseX::UndefTolerant::Attribute;
+
+  has 'bar' => (
+      traits => [ qw(MooseX::UndefTolerant::Attribute)],
+      is => 'ro',
+      isa => 'Num',
+      predicate => 'has_bar'
+  );
+
+  # Meanwhile, under the city...
+
+  # Doesn't explode
+  my $class = My::Class->new(bar => undef);
+  $class->has_bar # False!
+
+=head1 DESCRIPTION
+
+Applying this trait to your attribute makes it's initialization tolerant of
+of undef.  If you specify the value of undef to any of the attributes they
+will not be initialized (or will be set to the default, if applicable).
+Effectively behaving as if you had not provided a value at all.
+
+=cut