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Updated: Thursday, March 14, 2019
 
 

oo_define (1t)

Name

oo_define - 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

define(1t)                      TclOO Commands                      define(1t)



______________________________________________________________________________

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  argu-
       ment  or by the subcommand and following arg arguments; when the second
       is present, it is exactly as  if  all  the  arguments  from  subcommand
       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).

       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 inter-
              preter 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 han-
              dler.

       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; sub-
              class 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 argu-
              ments specified by the caller of the method.  The  cmdName  will
              always  be  resolved  using  the  rules of the invoking objects'
              namespaces, i.e., when cmdName is not fully-qualified, the  com-
              mand  will be searched for in each object's namespace, using the
              instances' namespace's path, or by looking in the global  names-
              pace.   The method will be exported if name starts with a lower-
              case letter, and non-exported otherwise.

       method name argList bodyScript
              This creates or updates a method that is implemented as a proce-
              dure-like  script.  The  name  of the method is name, the formal
              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 evalu-
              ated,  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).  Does  not  change
              the  export  status of the method; if it was exported before, it
              will be afterwards.

       self subcommand arg ...

       self script
              This command is equivalent to calling oo::objdefine on the class
              being  defined  (see CONFIGURING OBJECTS below for a description
              of the supported values of subcommand). It follows the same gen-
              eral   pattern  of  argument  handling  as  the  oo::define  and
              oo::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  com-
              mand  visible  in  each  object's  context)  by  the class being
              defined. Note  that  the  methods  themselves  may  be  actually
              defined  by a superclass; subclass unexports override superclass
              visibility, and may be overridden by instance unexports.

       variable ?-slotOperation? ?name ...?
              This slot (see SLOTTED DEFINITIONS below) arranges for  each  of |
              the  named  variables  to be automatically made available in the |
              methods, constructor and destructor declared by the class  being |
              defined.  Each variable name must not have any namespace separa- |
              tors and must not look like an array access. All variables  will |
              be  actually  present in the instance object on which the method |
              is executed. Note that the variable lists declared by  a  super- |
              class or subclass are completely disjoint, as are variable lists |
              declared by instances; the list of variable names  is  just  for |
              methods  (and  constructors  and  destructors)  declared by this |
              class. By default, this slot works by appending.

   CONFIGURING OBJECTS
       The following commands are supported in the  defScript  for  oo::objde-
       fine, each of which may also be used in the subcommand form:

       class className
              This allows the class of an object to be changed after creation.
              Note that the class's constructors are not called when  this  is
              done,  and  so  the  object may well be in an inconsistent state
              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. Does not
              affect the classes that the object is an instance of.

       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-exis-
              tent  method  to  be named. Note that the actual list of filters
              also depends on the filters set upon any classes that the object
              is an instance of.  By default, this slot works by appending.    |

       forward name cmdName ?arg ...?
              This  creates  or updates a forwarded object method called name.
              The method is defined be forwarded to the  command  called  cmd-
              Name,  with  additional  arguments, arg etc., added before those
              arguments specified by the caller of the method. Forwarded meth-
              ods  should  be  deleted using the method subcommand. The method
              will be exported if name starts with a  lower-case  letter,  and
              non-exported otherwise.

       method name argList bodyScript
              This  creates,  updates or deletes an object method. The name of
              the method is name, the formal arguments to the method  (defined
              using  the  same  format  as  for  the Tcl proc command) will be
              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.
              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  visi-
              ble  in  the object's context) by the object being defined. Note
              that the methods themselves may be actually defined by a  class;
              instance unexports override class visibility.

       variable ?-slotOperation? ?name ...?
              This  slot  (see SLOTTED DEFINITIONS below) arranges for each of |
              the named variables to be automatically made  available  in  the |
              methods  declared  by  the  object being defined.  Each variable |
              name must not have any namespace separators and  must  not  look |
              like  an array access. All variables will be actually present in |
              the object on which the method is executed. Note that the  vari- |
              able  lists  declared  by  the  classes  and mixins of which the |
              object is an instance are completely disjoint; the list of vari- |
              able  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 con- |
       tents of the slot. The class defines three operations (as methods) that |
       may be done on the slot:

       slot -append ?member ...?
              This appends the given member elements to the slot definition.   |

       slot -clear
              This sets the slot definition to the empty list.                 |

       slot -set ?member ...?
              This  replaces  the  slot  definition with the given member ele- |
              ments.                                                           |

       A consequence of this is that any use of  a  slot's  default  operation |
       where  the first member argument begins with a hyphen will be an error. |
       One of the above operations should be used explicitly in those  circum- |
       stances.                                                                |

   SLOT IMPLEMENTATION                                                         |
       Internally, slot objects also define a method --default-operation which |
       is forwarded to the default operation of the slot (thus, for the  class |
       "variable"  slot, this is forwarded to "my -append"), and these methods |
       which provide the implementation interface:

       slot Get
              Returns a list that is the current contents of  the  slot.  This |
              method  must  always  be  called from a stack frame created by a |
              call to oo::define or oo::objdefine.

       slot Set elementList
              Sets the contents of  the  slot  to  the  list  elementList  and |
              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 illus-
       trating four of the subcommands of them.

              oo::class create c
              c create o
              oo::define c method foo {} {
                  puts "world"
              }
              oo::objdefine o {
                  method bar {} {
                      my Foo "hello "
                      my foo
                  }
                  forward Foo ::puts -nonewline
                  unexport foo
              }
              o bar                -> prints "hello world"
              o foo                -> error "unknown method foo"
              o Foo Bar            -> error "unknown method Foo"
              oo::objdefine o renamemethod bar lollipop
              o lollipop           -> prints "hello world"

       This example shows how additional classes can be mixed into an  object.
       It also shows how mixin is a slot that supports appending:

              oo::object create inst
              inst m1              -> error "unknown method m1"
              inst m2              -> error "unknown method m2"

              oo::class create A {
                  method m1 {} {
                      puts "red brick"
                  }
              }
              oo::objdefine inst {
                  mixin A
              }
              inst m1              -> prints "red brick"
              inst m2              -> error "unknown method m2"

              oo::class create B {
                  method m2 {} {
                      puts "blue brick"
                  }
              }
              oo::objdefine inst {
                  mixin -append B
              }
              inst m1              -> prints "red brick"
              inst m2              -> prints "blue brick"


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | runtime/tcl-8    |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       next(n), oo::class(n), oo::object(n)

KEYWORDS
       class, definition, method, object, slot



NOTES
       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-
       core8.6.7-src.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.



TclOO                                 0.3                           define(1t)