DOKK / manpages / debian 11 / tcl8.6-doc / self.3tcl.en
self(3tcl) TclOO Commands self(3tcl) 







self - method call internal introspection








package require TclOO
self ?subcommand?










The self command, which should only be used from within the
    context of a call to a method (i.e. inside a method, constructor or
    destructor body) is used to allow the method to discover information about
    how it was called. It takes an argument, subcommand, that tells it
    what sort of information is actually desired; if omitted the result will be
    the same as if self object was invoked. The supported
    subcommands are:



  

  
This returns a two-element list describing the method implementations used
      to implement the current call chain. The first element is the same as
      would be reported by info object call for the current method
      (except that this also reports useful values from within constructors and
      destructors, whose names are reported as <constructor> and
      <destructor> respectively), and the second element is an
      index into the first element's list that indicates which actual
      implementation is currently executing (the first implementation to execute
      is always at index 0).

  

  
When the method was invoked from inside another object method, this
      subcommand returns a three element list describing the containing object
      and method. The first element describes the declaring object or class of
      the method, the second element is the name of the object on which the
      containing method was invoked, and the third element is the name of the
      method (with the strings <constructor> and
      <destructor> indicating constructors and destructors
      respectively).

  

  
This returns the name of the class that the current method was defined
      within. Note that this will change as the chain of method implementations
      is traversed with next, and that if the method was defined on an
      object then this will fail.






If you want the class of the current object, you need to use this
    other construct:






info object class [self object]







  

  
When invoked inside a filter, this subcommand returns a three element list
      describing the filter. The first element gives the name of the object or
      class that declared the filter (note that this may be different from the
      object or class that provided the implementation of the filter), the
      second element is either object or class depending on
      whether the declaring entity was an object or class, and the third element
      is the name of the filter.

  

  
This returns the name of the current method (with the strings
      <constructor> and <destructor> indicating
      constructors and destructors respectively).

  

  
This returns the name of the unique namespace of the object that the
      method was invoked upon.

  

  
When invoked from a method that is not at the end of a call chain (i.e.
      where the next command will invoke an actual method
      implementation), this subcommand returns a two element list describing the
      next element in the method call chain; the first element is the name of
      the class or object that declares the next part of the call chain, and the
      second element is the name of the method (with the strings
      <constructor> and <destructor> indicating
      constructors and destructors respectively). If invoked from a method that
      is at the end of a call chain, this subcommand returns the empty
    string.

  

  
This returns the name of the object that the method was invoked upon.

  

  
When invoked inside a filter implementation, this subcommand returns a two
      element list describing the method being filtered. The first element will
      be the name of the declarer of the method, and the second element will be
      the actual name of the method.










This example shows basic use of self to provide information
    about the current object:






oo::class create c {


    method foo {} {


        puts "this is the [self] object"


    }
}
c create a
c create b
a foo                → prints "this is the ::a object"
b foo                → prints "this is the ::b object"




This demonstrates what a method call chain looks like, and how
    traversing along it changes the index into it:






oo::class create c {


    method x {} {


        puts "Cls: [self call]"


    }
}
c create a
oo::objdefine a {


    method x {} {


        puts "Obj: [self call]"


        next


        puts "Obj: [self call]"


    }
}
a x     → Obj: {{method x object method} {method x ::c method}} 0


        → Cls: {{method x object method} {method x ::c method}} 1


        → Obj: {{method x object method} {method x ::c method}} 0










info(3tcl), next(3tcl)








call, introspection, object







  

    0.1
    TclOO