+---------+
 | ::nx::* |
 +---------+--------------------------------------Y
 |                                                |
 |  +---------+     instance of     +----------+  |
 |  |         |<....................|          |  |
 |  |  Class  |                     |  Object  |  |
 |  |         |....................>|          |  |
 |  +----+----+     subclass of     +-----+----+  |
 |       ^                           ^    ^       |
instance.|...........................|....|......./
      of |                           |    |
   +-----+-----+    subclass of      |    | instance
   |           |.....................|    | of
   |   /cls/   |    (by default)          |
   |           |                          |
   +-----------+                          |
         ^                                |
instance |.............(xor)..............|
      of |         +-----------+          |
         |.........|           |..........|
                   |   /obj/   |
                   |           |
                   +-----------+

obj ?public | private | protected? object alias ? -debug? ?-deprecated? 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.

To express deprecation of the alias method methodName, set the -deprecated flag. Deprecated methods remain usable from client code, but their usage will be signaled to the developer and/or can be tracked using ::nsf::deprecated. To register methodName with the debugger, set the -debug flag. Entering and exiting a method, which was flagged for debugging, is recorded by calling the redefinable callback procs ::nsf::debug::call and ::nsf::debug::exit, respectively. By default, these callbacks forward to ::nsf::log, which can also be customized at the script level.

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 lookup syntax configure. The configurationOption can be set and modified using configure.

% nx::Object create obj
::obj
% ::obj info lookup syntax configure
?-object-mixins /mixinreg .../? ?-class /class/? ?-object-filters /filterreg .../? ?/__initblock/?
% ::obj cget -class
::nx::Object

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 lookup syntax 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

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

obj copy ?newObjectName?

Creates a full and deep copy of a source object obj. The object's copy 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. The copy can be named explicitly, if newObjectName is provided, or it is named automatically (in the spirit of new of nx::Class).

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).

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-destruction 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.

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

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:

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.

obj ?public | protected | private? object forward ? -debug? ?-deprecated? 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.

To express deprecation of the forward method methodName, set the -deprecated flag. Deprecated methods remain usable from client code, but their usage will be signaled to the developer and/or can be tracked using ::nsf::deprecated. To register methodName with the debugger, set the -debug flag. Entering and exiting a method, which was flagged for debugging, is recorded by calling the redefinable callback procs ::nsf::debug::call and ::nsf::debug::exit, respectively. By default, these callbacks forward to ::nsf::log, which can also be customized at the script level.

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:

obj info baseclass

Returns the base class of obj. The base class is the class from which all NX objects are instantiated directly or indirectly (typically nx::Object).

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 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 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. If methodName is not the name of an existing method, an empty string is returned. To disambiguate between a non-existing method and an empty string as valid return value (e.g., for info object method args|parameters|args|...), use info object method exists.

Permitted values for option are:

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:

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:

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).

obj ?public | protected | private? object method ? -debug? ?-deprecated? 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).

To express deprecation of the method name, set the -deprecated flag. Deprecated methods remain usable from client code, but their usage will be signaled to the developer and/or can be tracked using ::nsf::deprecated. To register name with the debugger, set the -debug flag. Entering and exiting a method, which was flagged for debugging, is recorded by calling the redefinable callback procs ::nsf::debug::call and ::nsf::debug::exit, respectively. By default, these callbacks forward to ::nsf::log, which can also be customized at the script level.

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).

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.

obj object mixins submethod ?arg ...?

Accesses and modifies the list of mixin classes of obj using a specific setter or getter submethod:

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.

obj __object_configureparameter

Computes and returns the configuration options available for obj, to be consumed as method-parameter specification by configure.

obj object property ?-accessor public | protected | private? ?-class className? ?-configurable trueFalse? ?-incremental? ?-nocomplain? ? -trace set | get | default? 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:

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:

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

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.

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.

obj object variable ?-accessor public | protected | private? ?-incremental? ?-class className? ? -configurable trueFalse? ?-initblock script? ?-trace set | get | default? ?-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:

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:

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 create ::obj {
    # 1) print name of currently active object ('::obj')
    puts [current];
    # 2) object variables
    set :x 1; :object variable y 2;
    :public object method print {} {
      # 2.a) method-local variable
      set z 3;
      # 2.b) variable substitution using '$' and ':'
      puts ${:x}-${:y}-$z;
      # 2.c) reading variables using 'set'
      puts [set :x]-[set :y]-[set z];
      # 2.d) writing variables using 'set', 'incr', ...
      set :x 1; incr :y;
    }
    :public object method show {} {
      # 3.a) self-referential method call using ':'
      :print;
      # 3.b) self-referential method call using 'nx::current'
      [current] print;
      # 3.c) self-referential method call using 'nx::current object'
      [current object] print;
    }
    :show
  }