package Some_Class; 

 use strict; 

 CData1 = 

  

  

 no strict 

 It's true that you could work out a solution employing an DESTROY . Such complexity is uncalled for in most cases, and certainly in this one. 

  

  

 in the package into which those methods were compiled. When 

 you invoke the 

 $Some_Class::CData1--or in the method cloning 

 version, 

  

  

 Think of these class methods as executing in the context of 

 their base class, not in that of their derived class. 

  

 __The Eponymous Meta-Object__ 

  

  

 previous example is neither the most imaginative nor the 

 most intuitive of names. Is there something else that might 

 make more sense, be more useful, or both? 

  

 # it holds all class attributes, and also all instance attributes 

 # so the latter can be used for both initialization 

 # and translucency. 

  our %Vermin = ( # our() is new to perl5.6 

  # constructor method 

 # invoked as class method or object method 

 sub spawn { 

 my $obclass = shift; 

 to do so. 

  

  

  package Some_Class; 

 CData1 = 

 To make this more scalable as other class attributes are added, we can again register closures into the package symbol table to create accessor methods for them. 

  

  

  package Some_Class; 

 CData1 = 

 Requiring even your own class to use accessor methods like anybody else is probably a good thing. But demanding and expecting that everyone else, be they subclass or superclass, friend or foe, will all come to your object through mediation is more than just a good idea. It's absolutely critical to the model. Let there be in your mind no such thing as ``public'' data, nor even ``protected'' data, which is a seductive but ultimately destructive notion. Both will come back to bite at you. That's because as soon as you take that first step out of the solid position in which all state is considered completely private, save from the perspective of its own accessor methods, you have violated the envelope. And, having pierced that encapsulating envelope, you shall doubtless someday pay the price when future changes in the implementation break unrelated code. Considering that avoiding this infelicitous outcome was precisely why you consented to suffer the slings and arrows of obsequious abstraction by turning to object orientation in the first place, such breakage seems unfortunate in the extreme. 

  

  

 attributes. Since the actual method called is the one in the 

 object's derived class if this exists, you automatically get 

 per-class state this way. Any urge to provide an 

 unadvertised method to sneak out a reference to the 

 resisted. 

  

  

 As with any other overridden method, the implementation in 

  

  

  package Another_Class; 

 @ISA = qw(Some_Class); 

 CData1 = 

  sub CData1 { 

 my($self, $newvalue) = @_; 

 if (@_ 

 Key__ 

  

  

 As currently implemented, any code within the same scope as 

 hash directly. Is that ok? Is it acceptable or even 

 desirable to allow other parts of the implementation of this 

 class to access class attributes directly? 

  

  

  

  package Some_Class; 

  { # scope for ultra-private meta-object for class attributes 

 CData1 = 

 no strict 

  } 

 The closure above can be modified to take inheritance into account using the SUPER as shown previously. 

  

  # Here's the class meta-object, eponymously named. 

 # It holds all class data, and also all instance data 

 # so the latter can be used for both initialization 

 # and translucency. it's a template. 

  # constructor method 

 # invoked as class method or object method 

 sub spawn { 

 my $obclass = shift; 

 my $class = ref($obclass) $obclass; 

 my $self = {}; 

 bless($self, $class); 

 # init fields from invoking object, or omit if 

 # invoking object is the class to provide translucency 

 %$self = %$obclass if ref $obclass; 

 return $self; 

 } 

  # translucent accessor for 

  # handle class invocation 

 unless (ref $self) { 

 } 

  # handle object invocation 

 $self- 

  # class attribute accessor for 

  # instance destructor; invoked only as object method 

 sub DESTROY { 

 } 

  # detect whether an object attribute is translucent 

 # (typically?) invoked only as object method 

 sub is_translucent { 

 my($self, $attr) = @_; 

 return !defined $self- 

  # test for presence of attribute in class 

 # invoked as class method or object method 

 sub has_attribute { 

 my($self, $attr) = @_; 

 } 

 !!NOTES 

  

  

 (5.6) of perl--we hope. 

  

  

 You can't use file-scoped lexicals in conjunction with the 

 scope in which the module's methods wind up getting 

 compiled. 

  

  

  

 perltoot, perlobj, perlmod, and perlbot. 

  

  

 from CPAN are worth checking 

 out. 

 !!AUTHOR AND COPYRIGHT