[para] The last phase is also the most simple.
[para] It only invokes the Tcl command prefix associated with the
chosen [package cmdr::private] instance, providing it with the
[package cmdr::config] instance holding the parameter information
extracted from the command line as its single argument.
[para] For an example of very simple action implementations see
section [term {Simple backend}] of [term [vset TITLE_DSL]].
[para] All parameters declared for a [term private] are made
accessible through individual methods associated with each.
As example, a parameter with system name [var P] is mapped to the
method [method @P], with all instance methods provided by the
[package cmdr::parameter] class accessible as sub-methods.
This general access to all methods may be removed in the future,
restricting actions and callbacks to a safe subset.
[para] Another place providing information to actions is the root and
other actors of the command hierarchy itself, via [cmd common] blocks
whose value is managed by the system. Currently we have
[list_begin definitions]
[def [const *in-shell*]]
This block is read-only, and only found in the root actor.
Its value is managed by the framework.
It is a boolean flag indicating if an interactive shell is currently
active ([const true]) or not ([const false]).
This can be used to modulate command messages and other
context-dependent things.
[para] [emph Note] that the block will not exist until after the first
shell was active. This means that a missing [const *in-shell*] block
should be treated like [const false].
[def [const *config*]]
This block is read-only, and only found in the root actor.
Its value is managed by the framework, specifically by privates.
[para] It is a command name, i.e. object handle, to the active
instance of [class cmdr::config]. For regular parameters that is the
same handle given to them in their various callbacks. For a global
parameter however the active config object is what the parameter is
currently used by, whereas the callback argument is where it was
defined in and inherited from.
[para] This distinction is important when the global parameter has to
look at and work with non-global parameters of the active
private. These can only be found in the active context.
[def [const *prefix*]]
This block is read-only and found in the private actor for the
currently executing action command prefix, accessible through the
[package cmdr::config] instance method [method context].
Its value is managed by the framework.
It is a list of the command names used to reach the [term private]
instance.
This is not the logical path in the command hierarchy, but the actual
path taken, which may be through aliases.
[list_end]
[comment {@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@EDIT --todo-- figure out if we want this (safe para methods) in the docs/where
A first approximation of such a set can be found in the table below.
cmdline & True if the parameter accessible on command line. \\
config \arg{...} & Access to the methods of the container the
parameter belongs to, and thus all other
parameters of the private. \\
default & Default value, if specified. See \cmd{hasdefault}. \\
defered & True if the internal representation is generated on
demand. \\
description \arg{?detail?} & Help text. May be generated. \\
documented & True if the parameter is not hidden from help. \\
forget & Squash the internal representation. See also
\cmd{reset}. \\
generator & Command prefix to generate a default value (internal
representation). \\
hasdefault & True if a default value was specified. See
\cmd{default}. \\
help & Help structure describing the parameter. \\
interactive & True if the parameter allows interactive entry of its
value. \\
is \arg{type} & Check if the result of \cmd{type} matches the
argument. \\
isbool & True if the parametr is a boolean option. \\
list & True if the parameter holds a list of values. \\
lock \arg{reason} & For use in \cmd{when-set} callbacks. Allows
parameters to exclude each other's use. \\
locker & The \arg{reason} set by \cmd{lock}, if any. \\
name & The parameter's name. \\
options & List of option flags, if any. \\
ordered & True if the parameter is positional. \\
presence & True if the parameter is a boolean option not taking
arguments. \\
primary \arg {option} & True if the provided flag name is the
primary option to be recognized (instead of
an alias, or complement). \\
prompt & Text used as prompt during interactive entry. \\
required & True if the option is mandatory (\const(input) only). \\
reset & Squash internal and string representations. See also
\cmd{forget}. \\
self & The parameter's instance command \\
set \arg{value} & Programmatically set the string representation. \\
set? & True if the string representation was set. \\
string & Return the string representation, or error. \\
type & Parameter type. One of \const{input}, \const{option}, or
\const{state}. \\
validator & Command prefix used to validate the string
representation and transform it into the internal
representation. \\
value & Return the internal representation. May calculate it
now from the string representation. \\
when-complete & Command prefix invoked when the internal representation is set. \\
when-set & Command prefix invoked when the string representation is set. \\
}]
[para] Calling [method @P] without arguments is a shorthand for
calling ``@P value'', i.e. the retrieval of the parameter's internal
representation. Which may calculate the value if the call is the first
access and the parameter specified as [term defered].
