BEGIN {
eval "use SUPER 1.10";
plan skip_all => "SUPER 1.10 required for this test" if $@;
- plan tests => 4;
}
=pod
-This test demonstrates how simple it is to create Scala Style
-Class Mixin Composition. Below is an example taken from the
+This test demonstrates how simple it is to create Scala Style
+Class Mixin Composition. Below is an example taken from the
Scala web site's example section, and trancoded to Class::MOP.
NOTE:
We require SUPER for this test to handle the issue with SUPER::
-being determined at compile time.
+being determined at compile time.
L<http://scala.epfl.ch/intro/mixin.html>
-A class can only be used as a mixin in the definition of another
-class, if this other class extends a subclass of the superclass
-of the mixin. Since ColoredPoint3D extends Point3D and Point3D
-extends Point2D which is the superclass of ColoredPoint2D, the
+A class can only be used as a mixin in the definition of another
+class, if this other class extends a subclass of the superclass
+of the mixin. Since ColoredPoint3D extends Point3D and Point3D
+extends Point2D which is the superclass of ColoredPoint2D, the
code above is well-formed.
class Point2D(xc: Int, yc: Int) {
val y = yc;
override def toString() = "x = " + x + ", y = " + y;
}
-
+
class ColoredPoint2D(u: Int, v: Int, c: String) extends Point2D(u, v) {
val color = c;
def setColor(newCol: String): Unit = color = newCol;
override def toString() = super.toString() + ", col = " + color;
}
-
+
class Point3D(xc: Int, yc: Int, zc: Int) extends Point2D(xc, yc) {
val z = zc;
override def toString() = super.toString() + ", z = " + z;
}
-
+
class ColoredPoint3D(xc: Int, yc: Int, zc: Int, col: String)
extends Point3D(xc, yc, zc)
with ColoredPoint2D(xc, yc, col);
-
-
+
+
Console.println(new ColoredPoint3D(1, 2, 3, "blue").toString())
-
+
"x = 1, y = 2, z = 3, col = blue"
-
+
=cut
use Scalar::Util 'blessed';
use Carp 'confess';
sub ::with ($) {
- # fetch the metaclass for the
+ # fetch the metaclass for the
# caller and the mixin arg
my $metaclass = (caller)->meta;
my $mixin = (shift)->meta;
-
- # according to Scala, the
+
+ # according to Scala, the
# the superclass of our class
- # must be a subclass of the
+ # must be a subclass of the
# superclass of the mixin (see above)
my ($super_meta) = $metaclass->superclasses();
- my ($super_mixin) = $mixin->superclasses();
+ my ($super_mixin) = $mixin->superclasses();
($super_meta->isa($super_mixin))
|| confess "The superclass must extend a subclass of the superclass of the mixin";
-
+
# collect all the attributes
- # and clone them so they can
+ # and clone them so they can
# associate with the new class
- my @attributes = map {
- $mixin->get_attribute($_)->clone()
- } $mixin->get_attribute_list;
-
- my %methods = map {
+ my @attributes = map {
+ $mixin->get_attribute($_)->clone()
+ } $mixin->get_attribute_list;
+
+ my %methods = map {
my $method = $mixin->get_method($_);
# we want to ignore accessors since
# they will be created with the attrs
(blessed($method) && $method->isa('Class::MOP::Method::Accessor'))
? () : ($_ => $method)
- } $mixin->get_method_list;
+ } $mixin->get_method_list;
# NOTE:
- # I assume that locally defined methods
+ # I assume that locally defined methods
# and attributes get precedence over those
# from the mixin.
# add all the attributes in ....
foreach my $attr (@attributes) {
- $metaclass->add_attribute($attr)
+ $metaclass->add_attribute($attr)
unless $metaclass->has_attribute($attr->name);
}
- # add all the methods in ....
+ # add all the methods in ....
foreach my $method_name (keys %methods) {
- $metaclass->add_method($method_name => $methods{$method_name})
+ $metaclass->add_method($method_name => $methods{$method_name})
unless $metaclass->has_method($method_name);
- }
+ }
}
{
package Point2D;
use metaclass;
-
+
Point2D->meta->add_attribute('$x' => (
accessor => 'x',
init_arg => 'x',
));
-
+
Point2D->meta->add_attribute('$y' => (
accessor => 'y',
init_arg => 'y',
- ));
-
+ ));
+
sub new {
my $class = shift;
$class->meta->new_object(@_);
- }
-
+ }
+
sub toString {
my $self = shift;
"x = " . $self->x . ", y = " . $self->y;
}
-
+
package ColoredPoint2D;
our @ISA = ('Point2D');
-
+
ColoredPoint2D->meta->add_attribute('$color' => (
accessor => 'color',
init_arg => 'color',
- ));
-
+ ));
+
sub toString {
my $self = shift;
$self->SUPER() . ', col = ' . $self->color;
}
-
+
package Point3D;
our @ISA = ('Point2D');
-
+
Point3D->meta->add_attribute('$z' => (
accessor => 'z',
init_arg => 'z',
- ));
+ ));
sub toString {
my $self = shift;
$self->SUPER() . ', z = ' . $self->z;
}
-
+
package ColoredPoint3D;
- our @ISA = ('Point3D');
-
+ our @ISA = ('Point3D');
+
::with('ColoredPoint2D');
-
+
}
my $colored_point_3d = ColoredPoint3D->new(x => 1, y => 2, z => 3, color => 'blue');
'x = 1, y = 2, z = 3, col = blue',
'... got the right toString method');
-
+done_testing;
projects / gitmo/Class-MOP.git / blobdiff