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# oo::util(n) 1.2.3 tcllib "Utility commands for TclOO"

## Name

oo::util - Utility commands for TclOO

## Synopsis

- package require Tcl 8.5 9
- package require TclOO
- package require oo::util ?1.2.3?

- mymethod method ?arg...?
- classmethod name arguments body
- classvariable ?arg...?
- link method...
- link {alias method}...
- ooutil::singleton ?arg...?

## Description

This package provides a convenience command for the easy specification of instance methods as callback commands, like timers, file events, Tk bindings, etc.

## COMMANDS

mymethod method ?arg...?

  This command is available within instance methods. It takes a method name and, possibly, arguments for the method and returns a command prefix which, when executed, will invoke the named method of the object we are in, with the provided arguments, and any others supplied at the time of actual invokation.

  Note: The command is equivalent to and named after the command provided by the OO package snit for the same purpose.

classmethod name arguments body

  This command is available within class definitions. It takes a method name and, possibly, arguments for the method and creates a method on the class, available to a user of the class and of derived classes.

  Note: The command is equivalent to the command typemethod provided by the OO package snit for the same purpose.

  Example

      oo::class create ActiveRecord {
          classmethod find args { puts "[self] called with arguments: $args" }
      }
      oo::class create Table {
          superclass ActiveRecord
      }
      puts [Table find foo bar]
      # ======
      # which will write
      # ======
      # ::Table called with arguments: foo bar

classvariable ?arg...?

  This command is available within instance methods. It takes a series of variable names and makes them available in the method's scope. The originating scope for the variables is the class (instance) the object instance belongs to. In other words, the referenced variables are shared between all instances of their class.

  Note: The command is roughly equivalent to the command typevariable provided by the OO package snit for the same purpose. The difference is that it cannot be used in the class definition itself.

  Example:

      % oo::class create Foo {
          method bar {z} {
              classvariable x y
              return [incr x $z],[incr y]
          }
      }
      ::Foo
      % Foo create a
      ::a
      % Foo create b
      ::b
      % a bar 2
      2,1
      % a bar 3
      5,2
      % b bar 7
      12,3
      % b bar -1
      11,4
      % a bar 0
      11,5

link method...
link {alias method}...

  This command is available within instance methods. It takes a list of method names and/or pairs of alias- and method-name and makes the named methods available to all instance methods without requiring the my command.

  The alias name under which the method becomes available defaults to the method name, except where explicitly specified through an alias/method pair.

  Examples:

          link foo
          # The method foo is now directly accessible as foo instead of my foo.
          link {bar foo}
          # The method foo is now directly accessible as bar.
          link a b c
          # The methods a, b, and c all become directly acessible under their
          # own names.

  The main use of this command is expected to be in instance constructors, for convenience, or to set up some methods for use in a mini DSL.

ooutil::singleton ?arg...?

  This command is a meta-class, i.e. a variant of the builtin oo::class which ensures that it creates only a single instance of the classes defined with it.

  Syntax and results are like for oo::class.

  Example:

      % oo::class create example {
         self mixin singleton
         method foo {} {self}
      }
      ::example
      % [example new] foo
      ::oo::Obj22
      % [example new] foo
      ::oo::Obj22

## AUTHORS

Donal Fellows, Andreas Kupries

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category oo::util of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## See Also

snit(n)

## Keywords

TclOO, callback, class methods, class variables, command prefix, currying, method reference, my method, singleton

## Category

Utility

## Copyright

Copyright © 2011-2015 Andreas Kupries, BSD licensed