class(n) TclOO Commands class(n) ______________________________________________________________________________
NAME
oo::class - class of all classes
SYNOPSIS
package require TclOO
oo::class method ?arg ...?
CLASS HIERARCHY
oo::object
-> oo::class
______________________________________________________________________________
DESCRIPTION
Classes are objects that can manufacture other objects according to a
pattern stored in the factory object (the class). An instance of the
class is created by calling one of the class's factory methods, typi-
cally either create if an explicit name is being given, or new if an
arbitrary unique name is to be automatically selected.
The oo::class class is the class of all classes; every class is an
instance of this class, which is consequently an instance of itself.
This class is a subclass of oo::object, so every class is also an
object. Additional metaclasses (i.e., classes of classes) can be
defined if necessary by subclassing oo::class. Note that the oo::class
object hides the new method on itself, so new classes should always be
made using the create method.
CONSTRUCTOR
The constructor of the oo::class class takes an optional argument
which, if present, is sent to the oo::define command (along with the
name of the newly-created class) to allow the class to be conveniently
configured at creation time.
DESTRUCTOR
The oo::class class does not define an explicit destructor. However,
when a class is destroyed, all its subclasses and instances are also
destroyed, along with all objects that it has been mixed into.
EXPORTED METHODS
cls create name ?arg ...?
This creates a new instance of the class cls called name (which
is resolved within the calling context's namespace if not fully
qualified), passing the arguments, arg ..., to the constructor,
and (if that returns a successful result) returning the fully
qualified name of the created object (the result of the con-
structor is ignored). If the constructor fails (i.e. returns a
non-OK result) then the object is destroyed and the error mes-
sage is the result of this method call.
cls new ?arg ...?
This creates a new instance of the class cls with a new unique
name, passing the arguments, arg ..., to the constructor, and
(if that returns a successful result) returning the fully quali-
fied name of the created object (the result of the constructor
is ignored). If the constructor fails (i.e., returns a non-OK
result) then the object is destroyed and the error message is
the result of this method call.
Note that this method is not exported by the oo::class object
itself, so classes should not be created using this method.
NON-EXPORTED METHODS
The oo::class class supports the following non-exported methods:
cls createWithNamespace name nsName ?arg ...?
This creates a new instance of the class cls called name (which
is resolved within the calling context's namespace if not fully
qualified), passing the arguments, arg ..., to the constructor,
and (if that returns a successful result) returning the fully
qualified name of the created object (the result of the con-
structor is ignored). The name of the instance's internal names-
pace will be nsName unless that namespace already exists (when
an arbitrary name will be chosen instead). If the constructor
fails (i.e., returns a non-OK result) then the object is
destroyed and the error message is the result of this method
call.
EXAMPLES
This example defines a simple class hierarchy and creates a new
instance of it. It then invokes a method of the object before destroy-
ing the hierarchy and showing that the destruction is transitive.
oo::class create fruit {
method eat {} {
puts "yummy!"
}
}
oo::class create banana {
superclass fruit
constructor {} {
my variable peeled
set peeled 0
}
method peel {} {
my variable peeled
set peeled 1
puts "skin now off"
}
method edible? {} {
my variable peeled
return $peeled
}
method eat {} {
if {![my edible?]} {
my peel
}
next
}
}
set b [banana new]
$b eat -> prints "skin now off" and "yummy!"
fruit destroy
$b eat -> error "unknown command"
SEE ALSO
oo_define(n), oo_object(n)
KEYWORDS
class, metaclass, object
TclOO 0.1 class(n)
tcl 8.6.7 - Generated Thu Aug 10 18:55:44 CDT 2017