If you find yourself doing lots of "classical" Perl OO (with blessed hashes or arrays), you may want to take a look at Class::Struct. It provides a simple, but somewhat limited, way of producing your attribute methods. The nice things about Class::Struct are: it is a core module, and it is easy to understand.
If you really want to do OO with all the goodies, all the cool kids are using Moose. I haven't tried it in a project myself, but many people who I respect are using it with good success.
You can easily check to see if an argument is supplied to your setter methods:
use Carp qw(croak);
sub set_colour {
my $this = shift
croak 'set_colour requires an argument'
unless @_;
$this->{colour} = shift;
}
# if you like combined setter/getters
use Scalar::Util qw(reftype);
sub colour {
my $this = shift;
if ( @_ ) {
my $arg = shift;
croak 'Illegal value for method colour'
unless reftype $arg eq 'ARRAY';
$this->{colour} = $arg;
}
return @{ $this->{colour}||[] };
}
Some people prefer 'duck-typing' to checking reftype of a value. The basic idea is that if it quacks, it's a duck. So, to test if something is an array, we try treating it like one. If it works, then it's an array (even if it's really a tied hash behind the scenes).
sub colour {
my $this = shift;
if ( @_ ) {
my $arg = shift;
local $@;
croak 'Illegal value for method colour'
unless eval { @$arg; 1 };
$this->{colour} = $arg;
}
return @{ $this->{colour}||[] };
}
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