Provided by: tcl8.6-doc_8.6.13+dfsg-2_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