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delegation(n) [incr Tcl] delegation(n) 





NAME


itcl::delegation - delegate methods, procs or options to other
    objects


Parts of this description are "borrowed" from Tcl
    extension [snit], as the functionality is mostly identical.






WARNING!


This is new functionality in [incr Tcl] where the API can still
    change!!






SYNOPSIS


delegate method methodName to componentName ?as targetName?
delegate method methodName ?to componentName? using pattern
delegate method * ?to componentName? ?using pattern? ?except methodName methodName ...?
delegate proc procName to componentName ?as targetName?
delegate proc procName ?to componentName? using pattern
delegate proc * ?to componentName? ?using pattern? ?except procName procName ...?
delegate option optionSpec to componentName
delegate option optionSpec to componentName as targetname?
delegate option * to componentName
delegate option * to componentName except optionName optionname ...










DESCRIPTION


The delegate command is used inside an
    [incr Tcl] extendedclass/widget/widgetadaptor definition to
    delegate methods/procs/options to other objects for handling.



  

  
This form of delegate method delegates method methodName to component
      componentName. That is, when method methdoNameame is called on an instance
      of this type, the method and its arguments will be passed to the named
      component's command instead. That is, the following statement










delegate method wag to tail




is roughly equivalent to this explicitly defined method:






method wag {args} {


    uplevel $tail wag $args
}




The optional as clause allows you to specify the delegated
    method name and possibly add some arguments:






delegate method wagtail to tail as "wag briskly"




A method cannot be both locally defined and delegated.





  

  
In this form of the delegate statement, the using clause is used to
      specify the precise form of the command to which method name name is
      delegated. The to clause is optional, since the chosen command
      might not involve any particular component.






The value of the using clause is a list that may contain any or
    all of the following substitution codes; these codes are substituted with
    the described value to build the delegated command prefix. Note that the
    following two statements are equivalent:






delegate method wag to tail
delegate method wag to tail using "%c %m"




Each element of the list becomes a single element of the delegated
    command --it is never reparsed as a string.


Substitutions:



  
%%

  
This is replaced with a single "%". Thus, to pass the string
      "%c" to the command as an argument, you'd write
    "%%c".

  
%c

  
This is replaced with the named component's command.

  
%j

  
This is replaced by the method name; if the name consists of multiple
      tokens, they are joined by underscores ("_").

  
%m

  
This is replaced with the final token of the method name; if the method
      name has one token, this is identical to %M.

  
%M

  
This is replaced by the method name; if the name consists of multiple
      tokens, they are joined by space characters.

  
%n

  
This is replaced with the name of the instance's private namespace.

  
%s

  
This is replaced with the name of the instance command.

  
%t

  
This is replaced with the fully qualified type name.

  
%w

  
This is replaced with the original name of the instance command; for Itcl
      widgets and widget adaptors, it will be the Tk window name. It remains
      constant, even if the instance command is renamed.







  

  
In this form all unknown method names are delegeted to the specified
      component. The except clause can be used to specify a list of exceptions,
      i.e., method names that will not be so delegated. The using clause is
      defined as given above. In this form, the statement must contain the to
      clause, the using clause, or both.






In fact, the "*" can be a list of two or more tokens
    whose last element is "*", as in the following example:






delegate method {tail *} to tail




This implicitly defines the method tail whose subcommands will be
    delegated to the tail component.


The definitions for delegate proc ... are the same as for
    method, the only difference being, that this is for procs.





  

  

  

  

  

  

  

  
Defines a delegated option; the namespec is defined as for the option
      statement. When the configure, configurelist, or cget instance method is
      used to set or retrieve the option's value, the equivalent configure or
      cget command will be applied to the component as though the option was
      defined with the following -configuremethod and
    -cgetmethod:










method ConfigureMethod {option value} {


    $comp configure $option $value
}
method CgetMethod {option} {


    return [$comp cget $option]
}




Note that delegated options never appear in the
    itcl_options array. If the as clause is specified, then the target
    option name is used in place of name.





  

  
This form delegates all unknown options to the specified component. The
      except clause can be used to specify a list of exceptions, i.e., option
      names that will not be so delegated.






Warning: options can only be delegated to a component if it
    supports the configure and cget instance methods.


An option cannot be both locally defined and delegated. TBD:
    Continue from here.








KEYWORDS


delegation, option, method, proc







  

    4.0
    itcl