95 lines
2.9 KiB
Plaintext
95 lines
2.9 KiB
Plaintext
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'\"
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'\" Copyright (c) 1993-1998 Lucent Technologies, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.TH code n 3.0 itcl "[incr\ Tcl]"
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.so man.macros
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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itcl::code \- capture the namespace context for a code fragment
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.SH SYNOPSIS
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\fBitcl::code \fR?\fB-namespace \fIname\fR? \fIcommand \fR?\fIarg arg ...\fR?
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.BE
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.SH DESCRIPTION
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.PP
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Creates a scoped value for the specified \fIcommand\fR and its
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associated \fIarg\fR arguments. A scoped value is a list with three
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elements: the "\fC@scope\fR" keyword, a namespace context,
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and a value string. For example, the command
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.CS
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namespace foo {
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code puts "Hello World!"
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}
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.CE
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produces the scoped value:
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.CS
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@scope ::foo {puts {Hello World!}}
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.CE
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Note that the \fBcode\fR command captures the current namespace
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context. If the \fB-namespace\fR flag is specified, then the
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current context is ignored, and the \fIname\fR string is used
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as the namespace context.
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.PP
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Extensions like Tk execute ordinary code fragments in the global
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namespace. A scoped value captures a code fragment together with
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its namespace context in a way that allows it to be executed
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properly later. It is needed, for example, to wrap up code fragments
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when a Tk widget is used within a namespace:
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.CS
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namespace foo {
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private proc report {mesg} {
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puts "click: $mesg"
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}
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button .b1 -text "Push Me" \
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-command [code report "Hello World!"]
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pack .b1
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}
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.CE
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The code fragment associated with button \fC.b1\fR only makes
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sense in the context of namespace "foo". Furthermore, the
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"report" procedure is private, and can only be accessed within
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that namespace. The \fBcode\fR command wraps up the code
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fragment in a way that allows it to be executed properly
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when the button is pressed.
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.PP
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Also, note that the \fBcode\fR command preserves the integrity
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of arguments on the command line. This makes it a natural replacement
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for the \fBlist\fR command, which is often used to format Tcl code
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fragments. In other words, instead of using the \fBlist\fR command
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like this:
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.CS
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after 1000 [list puts "Hello $name!"]
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.CE
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use the \fBcode\fR command like this:
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.CS
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after 1000 [code puts "Hello $name!"]
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.CE
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This not only formats the command correctly, but also captures
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its namespace context.
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.PP
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Scoped commands can be invoked like ordinary code fragments, with
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or without the \fBeval\fR command. For example, the following
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statements work properly:
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.CS
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set cmd {@scope ::foo .b1}
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$cmd configure -background red
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set opts {-bg blue -fg white}
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eval $cmd configure $opts
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.CE
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Note that scoped commands by-pass the usual protection mechanisms;
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the command:
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.CS
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@scope ::foo {report {Hello World!}}
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.CE
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can be used to access the "foo::report" proc from any namespace
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context, even though it is private.
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.SH KEYWORDS
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scope, callback, namespace, public, protected, private
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