NAME

       oo::abstract - a class that does not allow direct instances of itself

SYNOPSIS

       package require tcl::oo

       oo::abstract method ?arg ...?

CLASS HIERARCHY

       oo::object
          → oo::class
              → oo::abstract
________________________________________________________________________________________________________________

DESCRIPTION

       Abstract  classes  are  classes  that can contain definitions, but which cannot be directly manufactured;
       they are intended to only ever be inherited from and instantiated indirectly. The characteristic  methods
       of oo::class (create and new) are not exported by an instance of oo::abstract.

       Note that oo::abstract is not itself an instance of oo::abstract.

   CONSTRUCTOR
       The  oo::abstract  class  does  not define an explicit constructor; this means that it is effectively the
       same as the constructor of the oo::class class.

   DESTRUCTOR
       The oo::abstract class does not define an explicit destructor; destroying an instance of it is just  like
       destroying an ordinary class (and will destroy all its subclasses).

   EXPORTED METHODS
       The oo::abstract class defines no new exported methods.

   NON-EXPORTED METHODS
       The oo::abstract class explicitly states that create, createWithNamespace, and new are unexported.

EXAMPLES

       This  example defines a simple class hierarchy and creates a new instance of it. It then invokes a method
       of the object before destroying the hierarchy and showing that the destruction is transitive.

              oo::abstract create fruit {
                  method eat {} {
                      puts "yummy!"
                  }
              }
              oo::class create banana {
                  superclass fruit
                  method peel {} {
                      puts "skin now off"
                  }
              }
              set b [banana new]
              $b peel              → prints 'skin now off'
              $b eat               → prints 'yummy!'
              set f [fruit new]    → error 'unknown method "new"...'

SEE ALSO

       oo::define(3tcl), oo::object(3tcl)

KEYWORDS

       abstract class, class, metaclass, object

TclOO                                                  0.3                                        abstract(3tcl)