Provided by: tcl8.6-doc_8.6.14+dfsg-1build1_all 
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 ...?
________________________________________________________________________________________________________________
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 argument or by the subcommand and following
arg arguments; when the second is present, it is exactly as if all the arguments from subcommand onwards
are made into a list and that list is used as the defScript argument.
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 superclasses' 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 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 object itself.
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 namespace as the current namespace. Destructors
should use the next command to call the superclasses' destructors. Note that destructors are not
called in all situations (e.g. if the interpreter is destroyed). If bodyScript is the empty
string, the destructor 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 handler.
export name ?name ...?
This arranges for each of the named methods, name, to be exported (i.e. usable outside an instance
through the instance object's command) by the class being defined. Note that the methods
themselves may be actually defined by a superclass; subclass exports override superclass
visibility, and may in turn be overridden 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 arguments
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 command will be
searched for in each object's namespace, using the instances' namespace's path, or by looking in
the global namespace. 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 procedure-like script. 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 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 otherwise; 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 instances 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 object 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
general pattern of argument handling as the oo::define and oo::objdefine commands, and “oo::define
cls self subcommand ...” operates 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 defined
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 exported (i.e. not usable outside the
instance through the instance 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 separators 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 superclass 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::objdefine, 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 unless 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., because it was created through oo::objdefine method). Does not
affect 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 exported (i.e. usable outside the object
through the object's command) by the object being defined. Note that the methods themselves 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-existent 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 cmdName, with additional arguments, arg etc., added before those arguments
specified by the caller of the method. Forwarded methods 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
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 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 provide an
equivalent capability). Does not change the export status of the method; if it was exported
before, it will be afterwards.
unexport name ?name ...?
This arranges for each of the named methods, name, to be not exported (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 variable │
lists declared by the classes and mixins of which the object is an instance are completely │
disjoint; the list of variable names is just for methods declared by this object. By default, 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 contents 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 elements. │
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 │
circumstances. │
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 returns 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 │
together, 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 illustrating 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