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Diffstat (limited to 'itcl/itcl/doc/code.n')
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diff --git a/itcl/itcl/doc/code.n b/itcl/itcl/doc/code.n new file mode 100644 index 00000000000..294ba7a41cd --- /dev/null +++ b/itcl/itcl/doc/code.n @@ -0,0 +1,96 @@ +'\" +'\" Copyright (c) 1993-1998 Lucent Technologies, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +'\" RCS: $Id$ +'\" +.so man.macros +.TH code n 3.0 itcl "[incr\ Tcl]" +.BS +'\" Note: do not modify the .SH NAME line immediately below! +.SH NAME +code \- capture the namespace context for a code fragment +.SH SYNOPSIS +\fBcode \fR?\fB-namespace \fIname\fR? \fIcommand \fR?\fIarg arg ...\fR? +.BE + +.SH DESCRIPTION +.PP +Creates a scoped value for the specified \fIcommand\fR and its +associated \fIarg\fR arguments. A scoped value is a list with three +elements: the "\fC@scope\fR" keyword, a namespace context, +and a value string. For example, the command +.CS +namespace foo { + code puts "Hello World!" +} +.CE +produces the scoped value: +.CS +@scope ::foo {puts {Hello World!}} +.CE +Note that the \fBcode\fR command captures the current namespace +context. If the \fB-namespace\fR flag is specified, then the +current context is ignored, and the \fIname\fR string is used +as the namespace context. +.PP +Extensions like Tk execute ordinary code fragments in the global +namespace. A scoped value captures a code fragment together with +its namespace context in a way that allows it to be executed +properly later. It is needed, for example, to wrap up code fragments +when a Tk widget is used within a namespace: +.CS +namespace foo { + private proc report {mesg} { + puts "click: $mesg" + } + + button .b1 -text "Push Me" \ + -command [code report "Hello World!"] + pack .b1 +} +.CE +The code fragment associated with button \fC.b1\fR only makes +sense in the context of namespace "foo". Furthermore, the +"report" procedure is private, and can only be accessed within +that namespace. The \fBcode\fR command wraps up the code +fragment in a way that allows it to be executed properly +when the button is pressed. +.PP +Also, note that the \fBcode\fR command preserves the integrity +of arguments on the command line. This makes it a natural replacement +for the \fBlist\fR command, which is often used to format Tcl code +fragments. In other words, instead of using the \fBlist\fR command +like this: +.CS +after 1000 [list puts "Hello $name!"] +.CE +use the \fBcode\fR command like this: +.CS +after 1000 [code puts "Hello $name!"] +.CE +This not only formats the command correctly, but also captures +its namespace context. +.PP +Scoped commands can be invoked like ordinary code fragments, with +or without the \fBeval\fR command. For example, the following +statements work properly: +.CS +set cmd {@scope ::foo .b1} +$cmd configure -background red + +set opts {-bg blue -fg white} +eval $cmd configure $opts +.CE +Note that scoped commands by-pass the usual protection mechanisms; +the command: +.CS +@scope ::foo {report {Hello World!}} +.CE +can be used to access the "foo::report" proc from any namespace +context, even though it is private. + +.SH KEYWORDS +scope, callback, namespace, public, protected, private |