abstract(n)

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

SYNOPSIS
package require TclOO
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(n), oo::object(n)

KEYWORDS
abstract class, class, metaclass, object