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abstract(3tcl) TclOO Commands abstract(3tcl) 





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







  

    0.3
    TclOO