bless do { my %self = (%{Colour->new($colour)}, %{Age->new($age)}); \%
+self }, $class;
So, you break encapsulation, and will depend on how things are implemented. If you're willing to break encapsulation, why even bother with OO?
The other solution is to go the inside-out object route. If your class doesn't care about the contents of the reference, then all is fine and dandy.
Inside-out objects aren't a silver bullet, and won't save the naive programmer.
package Colour {
use Scalar::Util 'refaddr';
my %colour;
sub new {
my $o = bless \do{my $var}, $_[0];
$colour{refaddr $o} = $_[1];
$o;
}
sub colour {$colour{refaddr $_[0]}}
};
package Age {
use Scalar::Util 'refaddr';
my %age;
sub new {
my $o = bless \do{my $var}, $_[0];
$age{refaddr $o} = $_[1];
$o;
}
sub age {$age{refaddr $_[0]}}
};
package Colour_and_Age {
our @ISA = qw[Age Colour];
use Scalar::Util 'refaddr';
sub new {
my ($class, $colour, $age) = @_;
... Now what? ...
}
}
Packages
Colour and
Age are written as inside-out objects, but because the same method constructs and initializes the object, the author of
Colour_and_Age is screwed. He doesn't even have the luxury of breaking encapsulation.
Now, if one separates object construction and object initialization, for instance:
use Scalar::Util 'refaddr';
package Colour {
use Scalar::Util 'refaddr';
my %colour;
sub new {bless \do{my $var}, $_[0]}
sub init {$colour{refaddr $_[0]} = $_[1]; $_[0]}
sub colour {$colour{refaddr $_[0]}}
};
package Age {
use Scalar::Util 'refaddr';
my %age;
sub new {bless \do{my $var}, $_[0]}
sub init {$age{refaddr $_[0]} = $_[1]; $_[0]}
sub age {$age{refaddr $_[0]}}
};
then one can use multiple inheritance without any problem:
package Colour_and_Age {
use Scalar::Util 'refaddr';
our @ISA = qw[Age Colour];
sub new {bless \do{my $var}, $_[0]}
sub init (
my ($self, $colour, $age) = @_;
$self->Colour::init($colour);
$self->Age::init($age);
$self;
}
};
my $o = Colour_and_Age::->new->init(red => 42);
It only takes a few more keystrokes to create your classes that way, and you aren't robbing any users from using your classes with multiple inheritance. Also note you don't need inside-out objects to separate constructions and initialization.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.