1configbody(n) [incr Tcl] configbody(n)
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8 itcl::configbody - change the "config" code for a public variable
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11 itcl::configbody className::varName body
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16 The configbody command is used outside of an [incr Tcl] class defini‐
17 tion to define or redefine the configuration code associated with a
18 public variable. Public variables act like configuration options for
19 an object. They can be modified outside the class scope using the
20 built-in configure method. Each variable can have a bit of "config"
21 code associate with it that is automatically executed when the variable
22 is configured. The configbody command can be used to define or rede‐
23 fine this body of code.
24 Like the body command, this facility allows a class definition to have
26 separate "interface" and "implementation" parts. The "interface" part
27 is a class command with declarations for methods, procs, instance vari‐
28 ables and common variables. The "implementation" part is a series of
29 body and configbody commands. If the "implementation" part is kept in
30 a separate file, it can be sourced again and again as bugs are fixed,
31 to support interactive development. When using the "tcl" mode in the
32 emacs editor, the "interface" and "implementation" parts can be kept in
33 the same file; as bugs are fixed, individual bodies can be highlighted
34 and sent to the test application.
35 The name "className::varName" identifies the public variable being
37 updated. If the body string starts with "@", it is treated as the sym‐
38 bolic name for a C procedure. Otherwise, it is treated as a Tcl com‐
39 mand script.
40 Symbolic names for C procedures are established by registering proce‐
42 dures via Itcl_RegisterC(). This is usually done in the Tcl_AppInit()
43 procedure, which is automatically called when the interpreter starts
44 up. In the following example, the procedure My_FooCmd() is registered
45 with the symbolic name "foo". This procedure can be referenced in the
46 configbody command as "@foo".
47 int
48 Tcl_AppInit(interp)
49 Tcl_Interp *interp; /* Interpreter for application. */
50 {
51 if (Itcl_Init(interp) == TCL_ERROR) {
52 return TCL_ERROR;
53 }
54 if (Itcl_RegisterC(interp, "foo", My_FooCmd) != TCL_OK) {
56 return TCL_ERROR;
57 }
58 }
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62 In the following example, a "File" class is defined to represent open
63 files. Whenever the "-name" option is configured, the existing file is
64 closed, and a new file is opened. Note that the "config" code for a
65 public variable is optional. The "-access" option, for example, does
66 not have it.
67 itcl::class File {
68 private variable fid ""
69 public variable name ""
71 public variable access "r"
72 constructor {args} {
74 eval configure $args
75 }
76 destructor {
77 if {$fid != ""} {
78 close $fid
79 }
80 }
81 method get {}
83 method put {line}
84 method eof {}
85 }
86 itcl::body File::get {} {
88 return [gets $fid]
89 }
90 itcl::body File::put {line} {
91 puts $fid $line
92 }
93 itcl::body File::eof {} {
94 return [::eof $fid]
95 }
96 itcl::configbody File::name {
98 if {$fid != ""} {
99 close $fid
100 }
101 set fid [open $name $access]
102 }
103 #
105 # See the File class in action:
106 #
107 File x
108 x configure -name /etc/passwd
110 while {![x eof]} {
111 puts "=> [x get]"
112 }
113 itcl::delete object x
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117 class, object, variable, configure
118itcl 3.0 configbody(n)