}
Or if you expect people to call not just C<< CLASS->new() >> but also
-C<< $obj->new() >>, then use something like this. The initialize()
-method used will be of whatever $class we blessed the
-object into:
+C<< $obj->new() >>, then use something like the following. (Note that using
+this to call new() on an instance does not automatically perform any
+copying. If you want a shallow or deep copy of an object, you'll have to
+specifically allow for that.) The initialize() method used will be of
+whatever $class we blessed the object into:
sub new {
my $this = shift;
C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS>
-You can also call C<UNIVERSAL::isa> as a subroutine with two arguments.
-The first does not need to be an object or even a reference. This
-allows you to check what a reference points to, or whether
-something is a reference of a given type. Example
+You can also call C<UNIVERSAL::isa> as a subroutine with two arguments. Of
+course, this will do the wrong thing if someone has overridden C<isa> in a
+class, so don't do it.
- if(UNIVERSAL::isa($ref, 'ARRAY')) {
- #...
- }
+If you need to determine whether you've received a valid invocant, use the
+C<blessed> function from L<Scalar::Util>:
-To determine if a reference is a blessed object, you can write
+ if (blessed($ref) && $ref->isa( 'Some::Class')) {
+ # ...
+ }
- print "It's an object\n" if UNIVERSAL::isa($val, 'UNIVERSAL');
+C<blessed> returns the name of the package the argument has been
+blessed into, or C<undef>.
=item can(METHOD)
if it does then a reference to the sub is returned, if it does not then
I<undef> is returned.
-C<UNIVERSAL::can> can also be called as a subroutine with two arguments.
-It'll always return I<undef> if its first argument isn't an object or a
-class name. So here's another way to check if a reference is a
-blessed object
-
- print "It's still an object\n" if UNIVERSAL::can($val, 'can');
-
-You can also use the C<blessed> function of Scalar::Util:
-
- use Scalar::Util 'blessed';
-
- my $blessing = blessed $suspected_object;
-
-C<blessed> returns the name of the package the argument has been
-blessed into, or C<undef>.
+C<UNIVERSAL::can> can also be called as a subroutine with two arguments. It'll
+always return I<undef> if its first argument isn't an object or a class name.
+The same caveats for calling C<UNIVERSAL::isa> directly apply here, too.
=item VERSION( [NEED] )
node such as one might use in a sophisticated tree structure:
sub new_node {
- my $self = shift;
- my $class = ref($self) || $self;
- my $node = {};
+ my $class = shift;
+ my $node = {};
$node->{LEFT} = $node->{RIGHT} = $node;
$node->{DATA} = [ @_ ];
return bless $node => $class;