define(3tcl) TclOO Commands define(3tcl)
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NAME
oo::define, oo::objdefine - define and configure classes and objects
SYNOPSIS
package require TclOO
oo::define class defScript
oo::define class subcommand arg ?arg ...?
oo::objdefine object defScript
oo::objdefine object subcommand arg ?arg ...?
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DESCRIPTION
The oo::define command is used to control the configuration of classes,
and the oo::objdefine command is used to control the configuration of
objects (including classes as instance objects), with the configuration
being applied to the entity named in the class or the object argument.
Configuring a class also updates the configuration of all subclasses of
the class and all objects that are instances of that class or which mix
it in (as modified by any per-instance configuration). The way in which
the configuration is done is controlled by either the defScript argu-
ment or by the subcommand and following arg arguments; when the second
is present, it is exactly as if all the arguments from subcommand on-
wards are made into a list and that list is used as the defScript argu-
ment.
CONFIGURING CLASSES
The following commands are supported in the defScript for oo::define,
each of which may also be used in the subcommand form:
constructor argList bodyScript
This creates or updates the constructor for a class. The formal
arguments to the constructor (defined using the same format as
for the Tcl proc command) will be argList, and the body of the
constructor will be bodyScript. When the body of the constructor
is evaluated, the current namespace of the constructor will be a
namespace that is unique to the object being constructed. Within
the constructor, the next command should be used to call the su-
perclasses' constructors. If bodyScript is the empty string, the
constructor will be deleted.
deletemethod name ?name ...?
This deletes each of the methods called name from a class. The
methods must have previously existed in that class. Does not af-
fect the superclasses of the class, nor does it affect the sub-
classes or instances of the class (except when they have a call
chain through the class being modified) or the class object it-
self.
destructor bodyScript
This creates or updates the destructor for a class. Destructors
take no arguments, and the body of the destructor will be
bodyScript. The destructor is called when objects of the class
are deleted, and when called will have the object's unique name-
space as the current namespace. Destructors should use the next
command to call the superclasses' destructors. Note that de-
structors are not called in all situations (e.g. if the inter-
preter is destroyed). If bodyScript is the empty string, the de-
structor will be deleted.
Note that errors during the evaluation of a destructor are not
returned to the code that causes the destruction of an object.
Instead, they are passed to the currently-defined bgerror han-
dler.
export name ?name ...?
This arranges for each of the named methods, name, to be ex-
ported (i.e. usable outside an instance through the instance ob-
ject's command) by the class being defined. Note that the meth-
ods themselves may be actually defined by a superclass; subclass
exports override superclass visibility, and may in turn be over-
ridden by instances.
filter ?-slotOperation? ?methodName ...?
This slot (see SLOTTED DEFINITIONS below) sets or updates the │
list of method names that are used to guard whether method call
to instances of the class may be called and what the method's
results are. Each methodName names a single filtering method
(which may be exposed or not exposed); it is not an error for a
non-existent method to be named since they may be defined by
subclasses. By default, this slot works by appending. │
forward name cmdName ?arg ...?
This creates or updates a forwarded method called name. The
method is defined be forwarded to the command called cmdName,
with additional arguments, arg etc., added before those argu-
ments specified by the caller of the method. The cmdName will
always be resolved using the rules of the invoking objects'
namespaces, i.e., when cmdName is not fully-qualified, the com-
mand will be searched for in each object's namespace, using the
instances' namespace's path, or by looking in the global name-
space. The method will be exported if name starts with a lower-
case letter, and non-exported otherwise.
method name argList bodyScript
This creates or updates a method that is implemented as a proce-
dure-like script. The name of the method is name, the formal ar-
guments to the method (defined using the same format as for the
Tcl proc command) will be argList, and the body of the method
will be bodyScript. When the body of the method is evaluated,
the current namespace of the method will be a namespace that is
unique to the current object. The method will be exported if
name starts with a lower-case letter, and non-exported other-
wise; this behavior can be overridden via export and unexport.
mixin ?-slotOperation? ?className ...?
This slot (see SLOTTED DEFINITIONS below) sets or updates the │
list of additional classes that are to be mixed into all the in-
stances of the class being defined. Each className argument
names a single class that is to be mixed in. By default, this │
slot works by replacement.
renamemethod fromName toName
This renames the method called fromName in a class to toName.
The method must have previously existed in the class, and toName
must not previously refer to a method in that class. Does not
affect the superclasses of the class, nor does it affect the
subclasses or instances of the class (except when they have a
call chain through the class being modified), or the class ob-
ject itself. Does not change the export status of the method; if
it was exported before, it will be afterwards.
self subcommand arg ...
self script
This command is equivalent to calling oo::objdefine on the class
being defined (see CONFIGURING OBJECTS below for a description
of the supported values of subcommand). It follows the same gen-
eral pattern of argument handling as the oo::define and oo::ob-
jdefine commands, and “oo::define cls self subcommand ...” op-
erates identically to “oo::objdefine cls subcommand ...”.
superclass ?-slotOperation? ?className ...?
This slot (see SLOTTED DEFINITIONS below) allows the alteration │
of the superclasses of the class being defined. Each className
argument names one class that is to be a superclass of the de-
fined class. Note that objects must not be changed from being
classes to being non-classes or vice-versa, that an empty parent
class is equivalent to oo::object, and that the parent classes
of oo::object and oo::class may not be modified. By default, │
this slot works by replacement.
unexport name ?name ...?
This arranges for each of the named methods, name, to be not ex-
ported (i.e. not usable outside the instance through the in-
stance object's command, but instead just through the my command
visible in each object's context) by the class being defined.
Note that the methods themselves may be actually defined by a
superclass; subclass unexports override superclass visibility,
and may be overridden by instance unexports.
variable ?-slotOperation? ?name ...?
This slot (see SLOTTED DEFINITIONS below) arranges for each of │
the named variables to be automatically made available in the │
methods, constructor and destructor declared by the class being │
defined. Each variable name must not have any namespace separa- │
tors and must not look like an array access. All variables will │
be actually present in the instance object on which the method │
is executed. Note that the variable lists declared by a super- │
class or subclass are completely disjoint, as are variable lists │
declared by instances; the list of variable names is just for │
methods (and constructors and destructors) declared by this │
class. By default, this slot works by appending.
CONFIGURING OBJECTS
The following commands are supported in the defScript for oo::objde-
fine, each of which may also be used in the subcommand form:
class className
This allows the class of an object to be changed after creation.
Note that the class's constructors are not called when this is
done, and so the object may well be in an inconsistent state un-
less additional configuration work is done.
deletemethod name ?name ...
This deletes each of the methods called name from an object. The
methods must have previously existed in that object (e.g., be-
cause it was created through oo::objdefine method). Does not af-
fect the classes that the object is an instance of, or remove
the exposure of those class-provided methods in the instance of
that class.
export name ?name ...?
This arranges for each of the named methods, name, to be ex-
ported (i.e. usable outside the object through the object's com-
mand) by the object being defined. Note that the methods them-
selves may be actually defined by a class or superclass; object
exports override class visibility.
filter ?-slotOperation? ?methodName ...?
This slot (see SLOTTED DEFINITIONS below) sets or updates the │
list of method names that are used to guard whether a method
call to the object may be called and what the method's results
are. Each methodName names a single filtering method (which may
be exposed or not exposed); it is not an error for a non-exis-
tent method to be named. Note that the actual list of filters
also depends on the filters set upon any classes that the object
is an instance of. By default, this slot works by appending. │
forward name cmdName ?arg ...?
This creates or updates a forwarded object method called name.
The method is defined be forwarded to the command called cmd-
Name, with additional arguments, arg etc., added before those
arguments specified by the caller of the method. Forwarded meth-
ods should be deleted using the method subcommand. The method
will be exported if name starts with a lower-case letter, and
non-exported otherwise.
method name argList bodyScript
This creates, updates or deletes an object method. The name of
the method is name, the formal arguments to the method (defined
using the same format as for the Tcl proc command) will be ar-
gList, and the body of the method will be bodyScript. When the
body of the method is evaluated, the current namespace of the
method will be a namespace that is unique to the object. The
method will be exported if name starts with a lower-case letter,
and non-exported otherwise.
mixin ?-slotOperation? ?className ...?
This slot (see SLOTTED DEFINITIONS below) sets or updates a per- │
object list of additional classes that are to be mixed into the
object. Each argument, className, names a single class that is
to be mixed in. By default, this slot works by replacement. │
renamemethod fromName toName
This renames the method called fromName in an object to toName.
The method must have previously existed in the object, and
toName must not previously refer to a method in that object.
Does not affect the classes that the object is an instance of
and cannot rename in an instance object the methods provided by
those classes (though a oo::objdefine forwarded method may pro-
vide an equivalent capability). Does not change the export sta-
tus of the method; if it was exported before, it will be after-
wards.
unexport name ?name ...?
This arranges for each of the named methods, name, to be not ex-
ported (i.e. not usable outside the object through the object's
command, but instead just through the my command visible in the
object's context) by the object being defined. Note that the
methods themselves may be actually defined by a class; instance
unexports override class visibility.
variable ?-slotOperation? ?name ...?
This slot (see SLOTTED DEFINITIONS below) arranges for each of │
the named variables to be automatically made available in the │
methods declared by the object being defined. Each variable │
name must not have any namespace separators and must not look │
like an array access. All variables will be actually present in │
the object on which the method is executed. Note that the vari- │
able lists declared by the classes and mixins of which the ob- │
ject is an instance are completely disjoint; the list of vari- │
able names is just for methods declared by this object. By de- │
fault, this slot works by appending. │
SLOTTED DEFINITIONS │
Some of the configurable definitions of a class or object are slotted │
definitions. This means that the configuration is implemented by a slot │
object, that is an instance of the class oo::Slot, which manages a list │
of values (class names, variable names, etc.) that comprises the con- │
tents of the slot. The class defines three operations (as methods) that │
may be done on the slot:
slot -append ?member ...?
This appends the given member elements to the slot definition. │
slot -clear
This sets the slot definition to the empty list. │
slot -set ?member ...?
This replaces the slot definition with the given member ele- │
ments. │
A consequence of this is that any use of a slot's default operation │
where the first member argument begins with a hyphen will be an error. │
One of the above operations should be used explicitly in those circum- │
stances. │
SLOT IMPLEMENTATION │
Internally, slot objects also define a method --default-operation which │
is forwarded to the default operation of the slot (thus, for the class │
“variable” slot, this is forwarded to “my -append”), and these methods │
which provide the implementation interface:
slot Get
Returns a list that is the current contents of the slot. This │
method must always be called from a stack frame created by a │
call to oo::define or oo::objdefine.
slot Set elementList
Sets the contents of the slot to the list elementList and re- │
turns the empty string. This method must always be called from a │
stack frame created by a call to oo::define or oo::objdefine. │
The implementation of these methods is slot-dependent (and responsible │
for accessing the correct part of the class or object definition). │
Slots also have an unknown method handler to tie all these pieces to- │
gether, and they hide their destroy method so that it is not invoked │
inadvertently. It is recommended that any user changes to the slot │
mechanism be restricted to defining new operations whose names start │
with a hyphen.
EXAMPLES
This example demonstrates how to use both forms of the oo::define and
oo::objdefine commands (they work in the same way), as well as illus-
trating four of the subcommands of them.
oo::class create c
c create o
oo::define c method foo {} {
puts "world"
}
oo::objdefine o {
method bar {} {
my Foo "hello "
my foo
}
forward Foo ::puts -nonewline
unexport foo
}
o bar → prints "hello world"
o foo → error "unknown method foo"
o Foo Bar → error "unknown method Foo"
oo::objdefine o renamemethod bar lollipop
o lollipop → prints "hello world"
This example shows how additional classes can be mixed into an object.
It also shows how mixin is a slot that supports appending:
oo::object create inst
inst m1 → error "unknown method m1"
inst m2 → error "unknown method m2"
oo::class create A {
method m1 {} {
puts "red brick"
}
}
oo::objdefine inst {
mixin A
}
inst m1 → prints "red brick"
inst m2 → error "unknown method m2"
oo::class create B {
method m2 {} {
puts "blue brick"
}
}
oo::objdefine inst {
mixin -append B
}
inst m1 → prints "red brick"
inst m2 → prints "blue brick"
SEE ALSO
next(3tcl), oo::class(3tcl), oo::object(3tcl)
KEYWORDS
class, definition, method, object, slot
TclOO 0.3 define(3tcl)
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