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/wid-
get/widgetadaptor definition to delegate methods/procs/options to other
objects for handling.
delegate method methodName to componentName ?as targetName?
This form of delegate method delegates method methodName to com-
ponent 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.
delegate method methodName ?to componentName? using pattern
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 substi-
tuted 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 dele-
gated 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.
delegate method * ?to componentName? ?using pattern? ?except methodName
methodName ...?
In this form all unknown method names are delegeted to the spec-
ified 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.
delegate option namespec to comp
delegate option namespec to comp as target
delegate option * to comp
delegate option * to comp except exceptions
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.
delegate option * ?except optionName optionName ...?
This form delegates all unknown options to the specified compo-
nent. The except clause can be used to specify a list of excep-
tions, i.e., option names that will not be so delegated.
Warning: options can only be delegated to a component if it sup-
ports the configure and cget instance methods.
An option cannot be both locally defined and delegated. TBD:
Continue from here.
KEYWORDS
delegation, option, method, proc
itcl 4.0 delegation(n)
tcl 8.6.9 - Generated Fri Nov 16 19:08:56 CST 2018