Provided by: nsf_2.0.0-2_amd64 
NAME
nx::Object - API reference of the base class in the NX object system
SYNOPSIS
nx::Object create obj ?-object-mixins mixinSpec? ?-class newClassName? ?-object-filters
filterSpec? ?initBlock?
nx::Object new ?-object-mixins mixinSpec? ?-class newClassName? ?-object-filters
filterSpec? ?initBlock?
obj ?public | private | protected? object alias methodName ?-returns valueChecker? ?-frame
object | method? cmdName
obj cget configurationOption
obj configure ?configurationOption value ...?
obj contains ?-withnew trueFalse? ?-object objectName? ?-class className? cmds
obj copy newObjectName
obj delete object feature arg
obj destroy
obj eval arg ?arg ...?
obj object filters submethod ?arg ...?
obj ?public | protected | private? object forward methodName ?-prefix prefixName? ?-frame
object? ?-returns valueChecker? ?-verbose? ?target? ?arg ...?
obj info children ?-type className? ?pattern?
obj info class
obj info has ?mixin | namespace | type? ?arg ...?
obj info lookup submethod ?arg ...?
obj info name
obj info info ?-asList?
obj info object filters ?-guards? ?pattern?
obj info object method option methodName
obj info object methods ?-callprotection level? ?-type methodType? ?-path? ?namePattern?
obj info object mixins ?-guards? ?pattern?
obj info object slots ?-type className? ?pattern?
obj info object variables ?pattern?
obj info parent
obj info precedence ?-intrinsic? ?pattern?
obj info variable option handle
obj info vars ?pattern?
obj ?public | protected | private? object method name parameters ?-checkalways? ?-returns
valueChecker? body
obj move newObjectName
obj object mixins submethod ?arg ...?
obj object property ?-accessor public | protected | private? ?-configurable trueFalse?
?-incremental? ?-class className? ?-nocomplain? spec ?initBlock?
obj require namespace
obj require ?public | protected | private? object method methodName
obj unknown unknownMethodName ?arg ...?
obj object variable ?-accessor public | protected | private? ?-incremental? ?-class
className? ?-configurable trueFalse? ?-initblock script? ?-nocomplain? spec ?defaultValue?
_________________________________________________________________
DESCRIPTION
nx::Object is the base class of the NX object system. All objects defined in NX are
(direct or indirect) instances of this base class. The methods provided by the nx::Object
base class are available to all objects and to all classes defined in NX.
+---------+
| ::nx::* |
+---------+--------------------------------------Y
| |
| +---------+ instance of +----------+ |
| | |<....................| | |
| | Class | | Object | |
| | |....................>| | |
| +----+----+ subclass of +-----+----+ |
| ^ ^ ^ |
instance.|...........................|....|......./
of | | |
+-----+-----+ subclass of | | instance
| |.....................| | of
| /cls/ | (by default) |
| | |
+-----------+ |
^ |
instance |.............(xor)..............|
of | +-----------+ |
|.........| |..........|
| /obj/ |
| |
+-----------+
NX allows for creating and for using objects (e.g. obj) which are instantiated from the
base class nx::Object directly. Typical use cases are singletons and anonymous, inline
objects. In such use cases, NX does not require creating an intermediate application class
(e.g. cls), which specializes the base class nx::Object by default, beforehand.
Objects (e.g. obj) which are creating by instantiating a previously defined application
class (e.g. cls) are indirect instances of nx::Object.
Direct instances of nx::Object can be created as follows:
nx::Object create obj ?-object-mixins mixinSpec? ?-class newClassName? ?-object-filters
filterSpec? ?initBlock?
To create a direct instance of nx::Object having an explicit name obj, use create
on nx::Object. Note that create is defined by nx::Class and is available to
nx::Object being an instance of nx::Class. This way, singleton objects can be
created, for example.
nx::Object new ?-object-mixins mixinSpec? ?-class newClassName? ?-object-filters
filterSpec? ?initBlock?
To create a direct instance of nx::Object having an automatically assigned, implict
object name, use new on nx::Object. Note that new is defined by nx::Class and is
available to nx::Object being an instance of nx::Class. Using new allows for
creating anonymous, inline objects, for example.
The configuration options for direct and indirect instances of nx::Object, which can be
passed when calling create and new, are documented in the subsequent section.
CONFIGURATION OPTIONS FOR INSTANCES OF NX::OBJECT
Configuration options can be used for configuring objects during their creation by passing
the options as non-positional arguments into calls of new and create (see nx::Class). An
existing object can be queried for its current configuration using cget and it can be re-
configured using configure. Legal configuration options are:
-class ?className?
Retrieves the current class of the object or sets the object's class to className,
if provided.
-object-filters ?filterMethods?
Retrieves the list of currently active per-object filter methods or sets a list of
per-object filter methods, if filterMethods is provided.
-object-mixins ?mixinSpecs?
If mixinSpecs is not specified, retrieves the list of currently active per-object
mixin specifications. If mixinSpecs is specified, sets a list of per-object mixin
specifications to become active. mixin classes are returned or set in terms of a
list of mixin specifications.
METHODS FOR INSTANCES OF NX::OBJECT
alias
obj ?public | private | protected? object alias methodName ?-returns valueChecker?
?-frame object | method? cmdName
Define an alias method for the given object. The resulting method registers
a pre-existing Tcl command cmdName under the (alias) name methodName with
the object. If cmdName refers to another method, the corresponding argument
should be a valid method handle. If a Tcl command (e.g., a proc), the
argument should be a fully qualified Tcl command name. If aliasing a
subcommand (e.g., array exists) of a Tcl namespace ensemble (e.g., array),
cmdName must hold the fully qualified subcommand name (and not the ensemble
name of the subcommand).
As for a regular object method, -returns allows for setting a value checker
on the values returned by the aliased command cmdName.
When creating an alias method for a C-implemented Tcl command (i.e., command
defined using the Tcl/NX C-API), -frame sets the scope for variable
references used in the aliased command. If the provided value is object,
then variable references will be resolved in the context of the called
object, i.e., the object upon which the alias method is invoked, as if they
were object variables. There is no need for using the colon-prefix notation
for identifying object variables. If the value is method, then the aliased
command will be executed as a regular method call. The command is aware of
its called-object context; i.e., it can resolve ::nx::self. In addition, the
alias method has access to the method-call context (e.g., nx::next). If
-frame is omitted, and by default, the variable references will resolve in
the context of the caller of the alias method.
cget
obj cget configurationOption
The method is used to obtain the current value of configurationOption for
obj. The configuration options available for querying through cget are
determined by the configurable properties defined by the class hierarchy of
obj. The queriable configuration options for obj can be obtained by calling
info configure. The configurationOption can be set and modified using
configure.
% nx::Object create obj
::obj
% ::obj info configure
?-object-mixins /mixinreg .../? ?-class /class/? ?-object-filters /filterreg .../? ?/__initblock/?
% ::obj cget -class
::nx::Object
configure
obj configure ?configurationOption value ...?
This method sets configuration options on an object. The configuration
options available for setting on obj are determined by the configurable
properties defined by the class hierarchy of obj. The settable configuration
options for obj can be obtained by calling info configure. Furthermore,
configure is also called during object construction. Under object
construction, it receives the arguments passed into calls of create and new.
Options set using configure can be retrieved using cget.
% nx::Class create Foo {:property x}
::Foo
% Foo create f1 -x 101
::f1
% f1 cget -x
101
% f1 configure -x 200
% f1 cget -x
200
contains
obj contains ?-withnew trueFalse? ?-object objectName? ?-class className? cmds
This method acts as a builder for nested object structures. Object and class
construction statements passed to this method as its last argument cmds are
evaluated in a way so that the receiver object obj becomes the parent of the
newly constructed objects and classes. This is realized by setting
explicitly the namespace for constructing relatively named objects. Fully
qualified object names in cmds evade the nesting.
-withnew requests the automatic rescoping of objects created using new so
that they become nested into the receiver object obj, rather than being
created in the default namespace for autonamed objects (i.e., ::nsf). If
turned off, autonamed objects do not become children of obj.
The parent object objectName to be used instead of obj can be specified
using -object. If this explicitly set parent object does not exist prior to
calling contains, it will be created on the fly as a direct instance of
nx::Object. Alternatively, using -class, a class className other than
nx::Object for the on-the-fly creation of objectName can be provided.
% nx::Class create Window {
:contains {
#
# Become children of Window, implicitly
#
nx::Class create Header; # Window::Header
nx::Object create Panel; # Window::Panel
}
#
# Explicitly declared a child of Window using [self]
#
nx::Class create [self]::Slider; # Window::Slider
#
# Fully-qualified objects do not become nested
#
nx::Class create ::Door; # ::Door
}
::Window
% ::Window info children
::Window::Panel ::Window::Header ::Window::Slider
copy
obj copy newObjectName
Creates a full and deep copy of a source object obj. The object's copy
newObjectName features all structural and behavioral properties of the
source object, including object variables, per-object methods, nested
objects, slot objects, namespaces, filters, mixins, and traces.
delete
obj delete object feature arg
This method serves as the equivalent to Tcl's rename for removing structural
(properties, variables) and behavioral features (methods) of the object:
obj delete object property propertyName
obj delete object variable variableName
obj delete object method methodName
Removes a property propertyName, variable variableName, and method
methodName, respectively, previously defined for the scope of the object.
delete object method can be equally used for removing regular methods (see
object method), an alias method (see object alias), and a forwarder method
(see object forward).
destroy
obj destroy
This method allows for explicitly destructing an object obj, potentially
prior to obj being destroyed by the object system (e.g. during the shutdown
of the object system upon calling exit):
[nx::Object new] destroy
By providing a custom implementation of destroy, the destruction procedure
of obj can be customized. Typically, once the application-specific
destruction logic has completed, a custom destroy will trigger the actual,
physical object destruction via next.
% [nx::Object create obj {
:public method destroy {} {
puts "destroying [self]"
next; # physical destruction
}
}] destroy
destroying ::obj
A customized object-desctruction scheme can be made shared between the
instances of a class, by defining the custom destroy for an application
class:
% nx::Class create Foo {
:method destroy {} {
puts "destroying [self]"
next; # physical destruction
}
}
::Foo
% Foo create f1
::f1
% f1 destroy
destroying ::f1
Physical destruction is performed by clearing the in-memory object storage
of obj. This is achieved by passing obj into a call to dealloc provided by
nx::Class. A near, scripted equivalent to the C-implemented destroy provided
by nx::Object would look as follows:
% Object method destroy {} {
[:info class] dealloc [self]
}
Note, however, that destroy is protected against application-level
redefinition. Trying to evaluate the above script snippet yields:
refuse to overwrite protected method 'destroy'; derive e.g. a sub-class!
A custom destroy must be provided as a refinement in a subclass of
nx::Object or in a mixin class.
eval
obj eval arg ?arg ...?
Evaluates a special Tcl script for the scope of obj in the style of Tcl's
eval. There are, however, notable differences to the standard eval: In this
script, the colon-prefix notation is available to dispatch to methods and to
access variables of obj. Script-local variables, which are thrown away once
the evaluation of the script has completed, can be defined to store
intermediate results.
% nx::Object create obj {
:object property {bar 1}
:public object method foo {x} { return $x }
}
::obj
% ::obj eval {
set y [:foo ${:bar}]
}
1
filters
obj object filters submethod ?arg ...?
Accesses and modifies the list of methods which are registered as filters
with obj using a specific setter or getter submethod:
obj object filters add spec ?index?
Inserts a single filter into the current list of filters of obj.
Using index, a position in the existing list of filters for inserting
the new filter can be set. If omitted, index defaults to the list
head (0).
obj object filters clear
Removes all filters from obj and returns the list of removed filters.
Clearing is equivalent to passing an empty list for filterSpecList to
object filter set.
obj object filters delete ?-nocomplain? specPattern
Removes a single filter from the current list of filters of obj whose
spec matches specPattern. specPattern can contain special matching
chars (see string match). object filters delete will throw an error
if there is no matching filter, unless -nocomplain is set.
obj object filters get
Returns the list of current filter specifications registered for obj.
obj object filters guard methodName ?expr?
If expr is specified, registers a guard expression expr with a filter
methodName. This requires that the filter methodName has been
previously set using object filters set or added using object filters
add. expr must be a valid Tcl expression (see expr). An empty string
for expr will clear the currently registered guard expression for
filter methodName.
If expr is omitted, returns the guard expression set on the filter
methodName defined for obj. If none is available, an empty string
will be returned.
obj object filters methods ?pattern?
If pattern is omitted, returns all filter names which are defined by
obj. By specifying pattern, the returned filters can be limited to
those whose names match patterns (see string match).
obj object filters set filterSpecList
filterSpecList takes a list of filter specs, with each spec being
itself either a one-element or a two-element list: methodName ?-guard
guardExpr?. methodName identifies an existing method of obj which
becomes registered as a filter. If having three elements, the third
element guardExpr will be stored as a guard expression of the filter.
This guard expression must be a valid Tcl expression (see expr). expr
is evaluated when obj receives a message to determine whether the
filter should intercept the message. Guard expressions allow for
realizing context-dependent or conditional filter composition.
Every methodName in a spec must resolve to an existing method in the scope
of the object. To access and to manipulate the list of filters of obj,
cget|configure -object-filters can also be used.
forward
obj ?public | protected | private? object forward methodName ?-prefix prefixName?
?-frame object? ?-returns valueChecker? ?-verbose? ?target? ?arg ...?
Define a forward method for the given object. The definition of a forward
method registers a predefined, but changeable list of forwarder arguments
under the (forwarder) name methodName. Upon calling the forward method, the
forwarder arguments are evaluated as a Tcl command call. That is, if
present, target is interpreted as a Tcl command (e.g., a Tcl proc or an
object) and the remainder of the forwarder arguments arg as arguments passed
into this command. The actual method arguments to the invocation of the
forward method itself are appended to the list of forwarder arguments. If
target is omitted, the value of methodName is implicitly set and used as
target. This way, when providing a fully-qualified Tcl command name as
methodName without target, the unqualified methodName (namespace tail) is
used as the forwarder name; while the fully-qualified one serves as the
target.
As for a regular object method, -returns allows for setting a value checker
on the values returned by the resulting Tcl command call. When passing
object to -frame, the resulting Tcl command is evaluated in the context of
the object receiving the forward method call. This way, variable names used
in the resulting execution of a command become resolved as object variables.
The list of forwarder arguments arg can contain as its elements a mix of
literal values and placeholders. Placeholders are prefixed with a percent
symbol (%) and substituted for concrete values upon calling the forward
method. These placeholders allow for constructing and for manipulating the
arguments to be passed into the resulting command call on the fly:
· %method becomes substituted for the name of the forward method, i.e.
methodName.
· %self becomes substituted for the name of the object receiving the
call of the forward method.
· %1 becomes substituted for the first method argument passed to the
call of forward method. This requires, in turn, that at least one
argument is passed along with the method call.
Alternatively, %1 accepts an optional argument defaults: {%1
defaults}. defaults must be a valid Tcl list of two elements. For
the first element, %1 is substituted when there is no first method
argument which can be consumed by %1. The second element is inserted
upon availability of a first method argument with the consumed
argument being appended right after the second list element. This
placeholder is typically used to define a pair of getter/setter
methods.
· {%@index value} becomes substituted for the specified value at
position index in the forwarder-arguments list, with index being
either a positive integer, a negative integer, or the literal value
end (such as in Tcl's lindex). Positive integers specify a list
position relative to the list head, negative integers give a position
relative to the list tail. Indexes for positioning placeholders in
the definition of a forward method are evaluated from left to right
and should be used in ascending order.
Note that value can be a literal or any of the placeholders (e.g.,
%method, %self). Position prefixes are exempted, they are evaluated
as %cmdName-placeholders in this context.
· {%argclindex list} becomes substituted for the nth element of the
provided list , with n corresponding to the number of method
arguments passed to the forward method call.
· %% is substituted for a single, literal percent symbol (%).
· %cmdName is substituted for the value returned from executing the Tcl
command cmdName. To pass arguments to cmdName, the placeholder should
be wrapped into a Tcl list: {%cmdName ?arg ...?}.
Consider using fully-qualified Tcl command names for cmdName to avoid
possible name conflicts with the predefined placeholders, e.g., %self
vs. %::nx::self.
To disambiguate the names of subcommands or methods, which potentially become
called by a forward method, a prefix prefixName can be set using -prefix. This
prefix is prepended automatically to the argument following target (i.e., a second
argument), if present. If missing, -prefix has no effect on the forward method
call.
To inspect and to debug the conversions performed by the above placeholders,
setting the switch -verbose will have the command list to be executed (i.e., after
substitution) printed using ::nsf::log (debugging level: notice) upon calling the
forward method.
info
obj info children ?-type className? ?pattern?
Retrieves the list of nested (or aggregated) objects of obj. The resulting
list contains the fully qualified names of the nested objects. If -type is
set, only nested objects which are direct or indirect instances of class
className are returned. Using pattern, only nested objects whose names match
pattern are returned. The pattern string can contain special matching
characters (see string match). This method allows for introspecting on
contains.
obj info class
Returns the fully qualified name of the current nx::Class of obj. In case of
re-classification (see configure), the returned class will be different from
the nx::Class from which obj was originally instantiated using create or
new.
obj info has ?mixin | namespace | type? ?arg ...?
obj info method has mixin className
Verifies whether obj has a given nx::Class className registered as a
mixin class (returns: true) or not (returns: false).
obj info has namespace
Checks whether the object has a companion Tcl namespace (returns:
true) or not (returns: false). The namespace could have been created
using, for example, object require namespace.
obj info has type className
Tests whether the nx::Class className is a type of the object
(returns: true) or not (returns: false). That is, the method checks
whether the object is a direct instance of className or an indirect
instance of one of the superclasses of className.
obj info lookup submethod ?arg ...?
A collection of submethods to retrieve structural features (e.g.
configuration options, slot objects) and behavioral features (e.g. methods,
filters) available for obj from the perspective of a client to obj. Features
provided by obj itself and by the classes in its current linearisation list
are considered.
obj info lookup configure parameters ?namePattern?
Returns all configuration options available for obj as a list of
method-parameter definitions. They can be used, for example, to
define a custom method refinement for configure. The returned
configuration options can be limited to those whose names match
pattern (see string match).
obj info lookup configure syntax
Returns all configuration options available for obj as a concrete-
syntax description to be used in human-understandable messages (e.g.
errors or warnings, documentation strings).
obj info lookup filter name
Returns the method handle for the filter method name, if currently
registered. If there is no filter name registered, an empty string is
returned.
obj info lookup filters ?-guards? ?namePattern?
Returns the method handles of all filters which are active on obj. By
turning on the switch -guards, the corresponding guard expressions,
if any, are also reported for each filter as a three-element list:
methodHandle -guard guardExpr. The returned filters can be limited to
those whose names match namePattern (see string match).
obj info lookup method name
Returns the method handle for a method name if a so-named method can
be invoked on obj. If there is no method name, an empty string is
returned.
obj info lookup methods ?namePattern?
Returns the names of all methods (including aliases and forwarders)
which can be invoked on obj. The returned methods can be limited to
those whose names match namePattern (see string match).
obj info lookup mixins ?-guards? ?namePattern?
Returns the object names of all mixin classes which are currently
active on obj. By turning on the switch -guards, the corresponding
guard expressions, if any, are also reported as a three-element list
for each mixin class: className -guard guardExpr. The returned mixin
classes can be limited to those whose names match namePattern (see
string match).
obj info lookup slots ?-type className? ?-source all | application | system?
?namePattern?
Returns the command names of all slot objects responsible for
managing properties, variables, and relations of obj. The returned
slot objects can be limited according to any or a combination of the
following criteria: First, slot objects can be filtered based on
their command names matching namePattern (see string match). Second,
-type allows one to select slot objects which are instantiated from a
subclass className of nx::Slot (default: nx::Slot) . Third, -source
restricts slot objects returned according to their provenance in
either the NX system classes or the application classes present in
the linearisation list of obj (default: all).
To extract details of each slot object, use the info submethods
available for each slot object.
obj info lookup variables
Returns the command names of all slot objects responsible for
managing properties and variables of obj, if provided by obj or the
classes in the linearisation list of obj.
This is equivalent to calling: obj info lookup slots -type
::nx::VariableSlot -source all ?namePattern?.
To extract details of each slot object, use the info submethods
available for each slot object.
obj info name
Returns the unqualified name of an object, i.e., the object name without any
namespace qualifiers.
obj info info ?-asList?
Returns the available submethods of the info method ensemble for obj, either
as a pretty-printed string or as a Tcl list (if the switch -asList is set)
for further processing.
obj info object filters ?-guards? ?pattern?
If pattern is omitted, returns all filter names which are defined by obj. By
turning on the switch -guards, the corresponding guard expressions, if any,
are also reported along with each filter as a three-element list: filterName
-guard guardExpr. By specifying pattern, the returned filters can be limited
to those whose names match patterns (see string match).
obj info object method option methodName
This introspection submethod provides access to the details of methodName
provided by obj. Permitted values for option are:
· args returns a list containing the parameter names of methodName, in
order of the method-parameter specification.
· body returns the body script of methodName.
· definition returns a canonical command list which allows for
(re-)define methodName.
· definitionhandle returns the method handle for a submethod in a
method ensemble from the perspective of obj as method provider.
methodName must contain a complete method path.
· exists returns 1 if there is a methodName provided by obj, returns 0
otherwise.
· handle returns the method handle for methodName.
· origin returns the aliased command if methodName is an alias method,
or an empty string otherwise.
· parameters returns the parameter specification of methodName as a
list of parameter names and type specifications.
· registrationhandle returns the method handle for a submethod in a
method ensemble from the perspective of the method caller. methodName
must contain a complete method path.
· returns gives the type specification defined for the return value of
methodName.
· submethods returns the names of all submethods of methodName, if
methodName is a method ensemble. Otherwise, an empty string is
returned.
· syntax returns the method parameters of methodName as a concrete-
syntax description to be used in human-understandable messages (e.g.,
errors or warnings, documentation strings).
· type returns whether methodName is a scripted method, an alias
method, a forwarder method, or a setter method.
obj info object methods ?-callprotection level? ?-type methodType? ?-path?
?namePattern?
Returns the names of all methods defined by obj. Methods covered include
those defined using object alias and object forward. The returned methods
can be limited to those whose names match namePattern (see string match).
By setting -callprotection, only methods of a certain call protection level
(public, protected, or private) will be returned. Methods of a specific type
can be requested using -type. The recognized values for methodType are:
· scripted denotes methods defined using object method;
· alias denotes alias methods defined using object alias;
· forwarder denotes forwarder methods defined using object forward;
· setter denotes methods defined using ::nsf::setter;
· all returns methods of any type, without restrictions (also the
default value);
obj info object mixins ?-guards? ?pattern?
If pattern is omitted, returns the object names of the mixin classes which
extend obj directly. By turning on the switch -guards, the corresponding
guard expressions, if any, are also reported along with each mixin as a
three-element list: className -guard guardExpr. The returned mixin classes
can be limited to those whose names match patterns (see string match).
obj info object slots ?-type className? ?pattern?
If pattern is not specified, returns the object names of all slot objects
defined by obj. The returned slot objects can be limited according to any or
a combination of the following criteria: First, slot objects can be filtered
based on their command names matching pattern (see string match). Second,
-type allows one to select slot objects which are instantiated from a
subclass className of nx::Slot (default: nx::Slot).
obj info object variables ?pattern?
If pattern is omitted, returns the object names of all slot objects provided
by obj which are responsible for managing properties and variables of obj.
Otherwise, only slot objects whose names match pattern are returned.
This is equivalent to calling: obj info object slots -type
::nx::VariableSlot pattern.
To extract details of each slot object, use the info submethods available
for each slot object.
obj info parent
Returns the fully qualified name of the parent object of obj, if any. If
there is no parent object, the name of the Tcl namespace containing obj
(e.g. "::") will be reported.
obj info precedence ?-intrinsic? ?pattern?
Lists the classes from which obj inherits structural (e.g. properties) and
behavioral features (e.g. methods) and methods, in order of the
linearisation scheme in NX. By setting the switch -intrinsic, only classes
which participate in superclass/subclass relationships (i.e., intrinsic
classes) are returned. If a pattern is provided only classes whose names
match pattern are returned. The pattern string can contain special matching
characters (see string match).
obj info variable option handle
Retrieves selected details about a variable represented by the given handle.
A handle can be obtained by querying obj using info object variables and
info lookup variables. Valid values for option are:
· name returns the variable name.
· parameter returns a canonical parameter specification eligible to
(re-)define the given variable (e.g. using object variable) in a new
context.
· definition returns a canonical representation of the definition
command used to create the variable in its current configuration.
obj info vars ?pattern?
Yields a list of Tcl variable names created and defined for the scope of
obj, i.e., object variables. The list can be limited to object variables
whose names match pattern. The pattern string can contain special matching
characters (see string match).
method
obj ?public | protected | private? object method name parameters ?-checkalways?
?-returns valueChecker? body
Defines a scripted method methodName for the scope of the object. The method
becomes part of the object's signature interface. Besides a methodName, the
method definition specifies the method parameters and a method body.
parameters accepts a Tcl list containing an arbitrary number of non-
positional and positional parameter definitions. Each parameter definition
comprises a parameter name, a parameter-specific value checker, and
parameter options.
The body contains the method implementation as a script block. In this body
script, the colon-prefix notation is available to denote an object variable
and a self call. In addition, the context of the object receiving the method
call (i.e., the message) can be accessed (e.g., using nx::self) and the call
stack can be introspected (e.g., using nx::current).
Optionally, -returns allows for setting a value checker on values returned
by the method implementation. By setting the switch -checkalways, value
checking on arguments and return value is guaranteed to be performed, even
if value checking is temporarily disabled; see nx::configure).
A method closely resembles a Tcl proc, but it differs in some important
aspects: First, a method can define non-positional parameters and value
checkers on arguments. Second, the script implementing the method body can
contain object-specific notation and commands (see above). Third, method
calls cannot be intercepted using Tcl trace. Note that an existing Tcl proc
can be registered as an alias method with the object (see object alias).
move
obj move newObjectName
Effectively renames an object. First, the source object obj is cloned into a
target object newObjectName using copy. Second, the source object obj is
destroyed by invoking destroy. move is also called internally when rename
is performed for a Tcl command representing an object.
mixins
obj object mixins submethod ?arg ...?
Accesses and modifies the list of mixin classes of obj using a specific
setter or getter submethod:
obj object mixins add spec ?index?
Inserts a single mixin class into the current list of mixin classes
of obj. Using index, a position in the existing list of mixin classes
for inserting the new mixin class can be set. If omitted, index
defaults to the list head (0).
obj object mixins classes ?pattern?
If pattern is omitted, returns the object names of the mixin classes
which extend obj directly. By specifying pattern, the returned mixin
classes can be limited to those whose names match pattern (see string
match).
obj object mixins clear
Removes all mixin classes from obj and returns the list of removed
mixin classes. Clearing is equivalent to passing an empty list for
mixinSpecList to object mixins set.
obj object mixins delete ?-nocomplain? specPattern
Removes a mixin class from a current list of mixin classes of obj
whose spec matches specPattern. specPattern can contain special
matching chars (see string match). object mixins delete will throw an
error if there is no matching mixin class, unless -nocomplain is set.
obj object mixins get
Returns the list of current mixin specifications.
obj object mixins guard className ?expr?
If expr is specified, a guard expression expr is registered with the
mixin class className. This requires that the corresponding mixin
class className has been previously set using object mixins set or
added using object mixins add. expr must be a valid Tcl expression
(see expr). An empty string for expr will clear the currently
registered guard expression for the mixin class className.
If expr is not specified, returns the active guard expression. If
none is available, an empty string will be returned.
obj object mixins set mixinSpecList
mixinSpecList represents a list of mixin class specs, with each spec
being itself either a one-element or a three-element list: className
?-guard guardExpr?. If having one element, the element will be
considered the className of the mixin class. If having three
elements, the third element guardExpr will be stored as a guard
expression of the mixin class. This guard expression will be
evaluated using expr when obj receives a message to determine if the
mixin is to be considered during method dispatch or not. Guard
expressions allow for realizing context-dependent or conditional
mixin composition.
At the time of setting the mixin relation, that is, calling object mixins,
every className as part of a spec must be an existing instance of nx::Class.
To access and to manipulate the list of mixin classes of obj, cget|configure
-object-mixins can also be used.
__object_configureparameter
obj __object_configureparameter
Computes and returns the configuration options available for obj, to be
consumed as method-parameter specification by configure.
property
obj object property ?-accessor public | protected | private? ?-configurable
trueFalse? ?-incremental? ?-class className? ?-nocomplain? spec ?initBlock?
Defines a property for the scope of the object. The spec provides the
property specification as a list holding at least one element or, maximum,
two elements: propertyName?:typeSpec? ?defaultValue?. The propertyName is
also used as to form the names of the getter/setter methods, if requested
(see -accessor). It is, optionally, equipped with a typeSpec following a
colon delimiter which specifies a value checker for the values which become
assigned to the property. The second, optional element sets a defaultValue
for this property.
If -accessor is set, a property will provide for a pair of getter and setter
methods:
obj propertyName set value
Sets the property propertyName to value.
obj propertyName get
Returns the current value of property propertyName.
obj propertyName unset
Removes the value store of propertyName (e.g., an object variable),
if existing.
The option value passed along -accessor sets the level of call protection
for the generated getter and setter methods: public, protected, or private.
By default, no getter and setter methods are created.
Turning on the switch -incremental provides a refined setter interface to
the value managed by the property. First, setting -incremental implies
requesting -accessor (set to public by default, if not specified
explicitly). Second, the managed value will be considered a valid Tcl list.
A multiplicity of 1..* is set by default, if not specified explicitly as
part of spec. Third, to manage this list value element-wise (incrementally),
two additional setter methods become available:
obj propertyName add element ?index?
Adding element to the managed list value, at the list position given
by index (by default: 0).
obj propertyName delete elementPattern
Removing one or multiple elements from the managed list value which
match elementPattern. elementPattern can contain matching characters
(see string match).
By setting -configurable to true (the default), the property can be accessed and
modified through cget and configure, respectively. If false, no configuration
option will become available via cget and configure.
If neither -accessor nor -configurable are requested, the value managed by the
property will have to be accessed and modified directly. If the property manages an
object variable, its value will be readable and writable using set and eval.
A property becomes implemented by a slot object under any of the following
conditions:
· -configurable equals true (by default).
· -accessor is one of public, protected, or private.
· -incremental is turned on.
· initBlock is a non-empty string.
Assuming default settings, every property is realized by a slot object.
Provided a slot object managing the property is to be created, a custom
class className from which this slot object is to be instantiated can be set
using -class. The default value is ::nx::VariableSlot.
The last argument initBlock accepts an optional Tcl script which is passed
into the initialization procedure (see configure) of the property's slot
object. See also initBlock for create and new.
By default, the property will ascertain that no (potentially) pre-existing
and equally named object variable will be overwritten when defining the
property. In case of a conflict, an error exception is thrown:
% Object create obj { set :x 1 }
::obj
% ::obj object property {x 2}
object ::obj has already an instance variable named 'x'
If the switch -nocomplain is on, this check is omitted (continuing the above
example):
% ::obj object property -nocomplain {x 2}
% ::obj eval {set :x}
2
require
obj require namespace
Create a Tcl namespace named after the object obj. All object variables
become available as namespace variables.
obj require ?public | protected | private? object method methodName
Attempts to register a method definition made available using
::nsf::method::provide under the name methodName with obj . The registered
method is subjected to default call protection (protected), if not set
explicitly.
unknown
obj unknown unknownMethodName ?arg ...?
This method is called implicitly whenever an unknown method is invoked.
unknownMethodName indicates the unresolvable method name, followed by the
remainder of the original argument vector as a number of arg of the
indirected method invocation.
variable
obj object variable ?-accessor public | protected | private? ?-incremental? ?-class
className? ?-configurable trueFalse? ?-initblock script? ?-nocomplain? spec
?defaultValue?
Defines a variable for the scope of the object. The spec provides the
variable specification: variableName?:typeSpec?. The variableName will be
used to name the underlying Tcl variable and the getter/setter methods, if
requested (see -accessor). spec is optionally equipped with a typeSpec
following a colon delimiter which specifies a value checker for the values
managed by the variable. Optionally, a defaultValue can be defined.
If -accessor is set explicitly, a variable will provide for a pair of getter
and setter methods:
obj variableName set varValue
Sets variableName to varValue.
obj variableName get
Returns the current value of variableName.
obj variableName unset
Removes variableName, if existing, underlying the property.
The option value passed along -accessor sets the level of call protection
for the getter and setter methods: public, protected, or private. By
default, no getter and setter methods are created.
Turning on the switch -incremental provides a refined setter interface to
the value managed by the variable. First, setting -incremental implies
requesting -accessor (public by default, if not specified explicitly).
Second, the managed value will be considered a valid Tcl list. A
multiplicity of 1..* is set by default, if not specified explicitly as part
of spec (see above). Third, to manage this list value element-wise
(incrementally), two additional setter operations become available:
obj variableName add element ?index?
Adding element to the managed list value, at the list position given
by index (by default: 0).
obj variableName delete elementPattern
Removing one or multiple elements from the managed list value which
match elementPattern. elementPattern can contain matching characters
(see string match).
By setting -configurable to true, the variable can be accessed and modified via
cget and configure, respectively. If false (the default), the interface based on
cget and configure will not become available. In this case, and provided that
-accessor is set, the variable can be accessed and modified via the getter/setter
methods. Alternatively, the underlying Tcl variable, which is represented by the
variable, can always be accessed and modified directly, e.g., using eval. By
default, -configurable is false.
A variable becomes implemented by a slot object under any of the following
conditions:
· -configurable equals true.
· -accessor is one of public, protected, or private.
· -incremental is turned on.
· -initblock is a non-empty string.
Provided a slot object managing the variable is to be created, a custom
class className from which this slot object is to be instantiated can be set
using -class. The default value is ::nx::VariableSlot.
Using -initblock, an optional Tcl script can be defined which becomes passed
into the initialization procedure (see configure) of the variable's slot
object. See also initBlock for create and new.
By default, the variable will ascertain that a pre-existing and equally
named object variable will not be overwritten when defining the variable. In
case of a conflict, an error exception is thrown:
% Object create obj { set :x 1 }
::obj
% ::obj object variable x 2
object ::obj has already an instance variable named 'x'
If the switch -nocomplain is on, this check is omitted (continuing the above
example):
% ::obj object variable -nocomplain x 2
% ::obj eval {set :x}
2
OBJECT SELF-REFERENCE
Objects are naturally recursive, with methods of an object ::obj frequently invoking other
methods in the same object ::obj and accessing ::obj's object variables. To represent
these self-references effectively in method bodies, and dependening on the usage scenario,
NX offers two alternative notations for self-references: one based on a special-purpose
syntax token ("colon prefix"), the other based on the command nx::current.
Both, the colon-prefix notation and nx::current, may be used only in method bodies and
scripts passed to eval. If they appear anywhere else, an error will be reported. There
are three main use cases for self-references:
[1] As a placeholder for the currently active object, nx::current can be used to
retrieve the object name.
[2] Reading and writing object variables directly (i.e. without getter/setter methods
in place) require the use of variable names carrying the prefix : ("colon-prefix
notation"). Internally, colon-prefixed variable names are processed using Tcl's
variable resolvers. Alternatively, one can provide for getter/setter methods for
object variables (see property and variable).
[3] Self-referential method calls can be defined via prefixing (:) the method names or,
alternatively, via nx::current. Internally, colon-prefixed method names are
processed using Tcl's command resolvers. The colon-prefix notation is recommended,
also because it has a (slight) performance advantage over nx::current which
requires two rather than one command evaluation per method call.
See the following listing for some examples corresponding to use cases 1--3:
Object create ::obj {
puts [current]; # 1) print name of currently active object ('::obj')
set :x 1; :object variable y 2;# 2) object variables
:public object method print {} {
set z 3; # 2.a) method-local variable
puts ${:x}-${:y}-$z; # 2.b) variable substitution using '$' and ':'
puts [set :x]-[set :y]-[set z]; # 2.c) reading variables using 'set'
set :x 1; incr :y; # 2.d) writing variables using 'set', 'incr', ...
}
:public object method show {} {
:print; # 3.a) self-referential method call using ':'
[current] print;# 3.b) self-referential method call using 'nx::current'
[current object] print; # 3.c) self-referential method call using 'nx::current object'
}
:show
}
COPYRIGHT
Copyright (c) 2014 Stefan Sobernig <stefan.sobernig@wu.ac.at>, Gustaf Neumann <gustaf.neumann@wu.ac.at>; available under the Creative Commons Attribution 3.0 Austria license (CC BY 3.0 AT).