| '\" |
| '\" 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: itcl.n,v 1.1 1998/07/27 18:42:01 stanton Exp $ |
| '\" |
| '\" The definitions below are for supplemental macros used in Tcl/Tk |
| '\" manual entries. |
| '\" |
| '\" .AP type name in/out ?indent? |
| '\" Start paragraph describing an argument to a library procedure. |
| '\" type is type of argument (int, etc.), in/out is either "in", "out", |
| '\" or "in/out" to describe whether procedure reads or modifies arg, |
| '\" and indent is equivalent to second arg of .IP (shouldn't ever be |
| '\" needed; use .AS below instead) |
| '\" |
| '\" .AS ?type? ?name? |
| '\" Give maximum sizes of arguments for setting tab stops. Type and |
| '\" name are examples of largest possible arguments that will be passed |
| '\" to .AP later. If args are omitted, default tab stops are used. |
| '\" |
| '\" .BS |
| '\" Start box enclosure. From here until next .BE, everything will be |
| '\" enclosed in one large box. |
| '\" |
| '\" .BE |
| '\" End of box enclosure. |
| '\" |
| '\" .CS |
| '\" Begin code excerpt. |
| '\" |
| '\" .CE |
| '\" End code excerpt. |
| '\" |
| '\" .VS ?version? ?br? |
| '\" Begin vertical sidebar, for use in marking newly-changed parts |
| '\" of man pages. The first argument is ignored and used for recording |
| '\" the version when the .VS was added, so that the sidebars can be |
| '\" found and removed when they reach a certain age. If another argument |
| '\" is present, then a line break is forced before starting the sidebar. |
| '\" |
| '\" .VE |
| '\" End of vertical sidebar. |
| '\" |
| '\" .DS |
| '\" Begin an indented unfilled display. |
| '\" |
| '\" .DE |
| '\" End of indented unfilled display. |
| '\" |
| '\" .SO |
| '\" Start of list of standard options for a Tk widget. The |
| '\" options follow on successive lines, in four columns separated |
| '\" by tabs. |
| '\" |
| '\" .SE |
| '\" End of list of standard options for a Tk widget. |
| '\" |
| '\" .OP cmdName dbName dbClass |
| '\" Start of description of a specific option. cmdName gives the |
| '\" option's name as specified in the class command, dbName gives |
| '\" the option's name in the option database, and dbClass gives |
| '\" the option's class in the option database. |
| '\" |
| '\" .UL arg1 arg2 |
| '\" Print arg1 underlined, then print arg2 normally. |
| '\" |
| '\" SCCS: @(#) man.macros 1.9 97/08/22 18:50:59 |
| '\" |
| '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
| .if t .wh -1.3i ^B |
| .nr ^l \n(.l |
| .ad b |
| '\" # Start an argument description |
| .de AP |
| .ie !"\\$4"" .TP \\$4 |
| .el \{\ |
| . ie !"\\$2"" .TP \\n()Cu |
| . el .TP 15 |
| .\} |
| .ie !"\\$3"" \{\ |
| .ta \\n()Au \\n()Bu |
| \&\\$1 \\fI\\$2\\fP (\\$3) |
| .\".b |
| .\} |
| .el \{\ |
| .br |
| .ie !"\\$2"" \{\ |
| \&\\$1 \\fI\\$2\\fP |
| .\} |
| .el \{\ |
| \&\\fI\\$1\\fP |
| .\} |
| .\} |
| .. |
| '\" # define tabbing values for .AP |
| .de AS |
| .nr )A 10n |
| .if !"\\$1"" .nr )A \\w'\\$1'u+3n |
| .nr )B \\n()Au+15n |
| .\" |
| .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n |
| .nr )C \\n()Bu+\\w'(in/out)'u+2n |
| .. |
| .AS Tcl_Interp Tcl_CreateInterp in/out |
| '\" # BS - start boxed text |
| '\" # ^y = starting y location |
| '\" # ^b = 1 |
| .de BS |
| .br |
| .mk ^y |
| .nr ^b 1u |
| .if n .nf |
| .if n .ti 0 |
| .if n \l'\\n(.lu\(ul' |
| .if n .fi |
| .. |
| '\" # BE - end boxed text (draw box now) |
| .de BE |
| .nf |
| .ti 0 |
| .mk ^t |
| .ie n \l'\\n(^lu\(ul' |
| .el \{\ |
| .\" Draw four-sided box normally, but don't draw top of |
| .\" box if the box started on an earlier page. |
| .ie !\\n(^b-1 \{\ |
| \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' |
| .\} |
| .el \}\ |
| \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' |
| .\} |
| .\} |
| .fi |
| .br |
| .nr ^b 0 |
| .. |
| '\" # VS - start vertical sidebar |
| '\" # ^Y = starting y location |
| '\" # ^v = 1 (for troff; for nroff this doesn't matter) |
| .de VS |
| .if !"\\$2"" .br |
| .mk ^Y |
| .ie n 'mc \s12\(br\s0 |
| .el .nr ^v 1u |
| .. |
| '\" # VE - end of vertical sidebar |
| .de VE |
| .ie n 'mc |
| .el \{\ |
| .ev 2 |
| .nf |
| .ti 0 |
| .mk ^t |
| \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' |
| .sp -1 |
| .fi |
| .ev |
| .\} |
| .nr ^v 0 |
| .. |
| '\" # Special macro to handle page bottom: finish off current |
| '\" # box/sidebar if in box/sidebar mode, then invoked standard |
| '\" # page bottom macro. |
| .de ^B |
| .ev 2 |
| 'ti 0 |
| 'nf |
| .mk ^t |
| .if \\n(^b \{\ |
| .\" Draw three-sided box if this is the box's first page, |
| .\" draw two sides but no top otherwise. |
| .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c |
| .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c |
| .\} |
| .if \\n(^v \{\ |
| .nr ^x \\n(^tu+1v-\\n(^Yu |
| \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c |
| .\} |
| .bp |
| 'fi |
| .ev |
| .if \\n(^b \{\ |
| .mk ^y |
| .nr ^b 2 |
| .\} |
| .if \\n(^v \{\ |
| .mk ^Y |
| .\} |
| .. |
| '\" # DS - begin display |
| .de DS |
| .RS |
| .nf |
| .sp |
| .. |
| '\" # DE - end display |
| .de DE |
| .fi |
| .RE |
| .sp |
| .. |
| '\" # SO - start of list of standard options |
| .de SO |
| .SH "STANDARD OPTIONS" |
| .LP |
| .nf |
| .ta 4c 8c 12c |
| .ft B |
| .. |
| '\" # SE - end of list of standard options |
| .de SE |
| .fi |
| .ft R |
| .LP |
| See the \\fBoptions\\fR manual entry for details on the standard options. |
| .. |
| '\" # OP - start of full description for a single option |
| .de OP |
| .LP |
| .nf |
| .ta 4c |
| Command-Line Name: \\fB\\$1\\fR |
| Database Name: \\fB\\$2\\fR |
| Database Class: \\fB\\$3\\fR |
| .fi |
| .IP |
| .. |
| '\" # CS - begin code excerpt |
| .de CS |
| .RS |
| .nf |
| .ta .25i .5i .75i 1i |
| .. |
| '\" # CE - end code excerpt |
| .de CE |
| .fi |
| .RE |
| .. |
| .de UL |
| \\$1\l'|0\(ul'\\$2 |
| .. |
| .TH itcl n 3.0 itcl "[incr\ Tcl]" |
| .BS |
| '\" Note: do not modify the .SH NAME line immediately below! |
| .SH NAME |
| itcl \- object-oriented extensions to Tcl |
| .BE |
| |
| .SH DESCRIPTION |
| .PP |
| \fB[incr\ Tcl]\fR provides object-oriented extensions to Tcl, much as |
| C++ provides object-oriented extensions to C. The emphasis of this |
| work, however, is not to create a whiz-bang object-oriented |
| programming environment. Rather, it is to support more structured |
| programming practices in Tcl without changing the flavor of the language. |
| More than anything else, \fB[incr\ Tcl]\fR provides a means of |
| encapsulating related procedures together with their shared data |
| in a namespace that is hidden from the outside world. |
| It encourages better programming by promoting the object-oriented |
| "library" mindset. It also allows for code re-use through inheritance. |
| |
| .SH CLASSES |
| .PP |
| The fundamental construct in \fB[incr\ Tcl]\fR is the class definition. |
| Each class acts as a template for actual objects that can be created. |
| Each object has its own unique bundle of data, which contains instances |
| of the "variables" defined in the class. Special procedures called |
| "methods" are used to manipulate individual objects. Methods are just |
| like the operations that are used to manipulate Tk widgets. The |
| "\fBbutton\fR" widget, for example, has methods such as "flash" and |
| "invoke" that cause a particular button to blink and invoke its command. |
| .PP |
| Within the body of a method, the "variables" defined in the class |
| are automatically available. They need not be declared with anything |
| like the \fBglobal\fR command. Within another class method, a method |
| can be invoked like any other command\-simply by using its name. |
| From any other context, the method name must be prefaced by an object |
| name, which provides a context for the data that the method can access. |
| .PP |
| Each class has its own namespace containing things that are common |
| to all objects which belong to the class. For example, "common" data |
| members are shared by all objects in the class. They are global |
| variables that exist in the class namespace, but since they are |
| included in the class definition, they need not be declared using |
| the \fBglobal\fR command; they are automatically available to any |
| code executing in the class context. A class can also create |
| ordinary global variables, but these must be declared using the |
| \fBglobal\fR command each time they are used. |
| .PP |
| Classes can also have ordinary procedures declared as "procs". |
| Within another class method or proc, a proc can be invoked like |
| any other command\-simply by using its name. From any other context, |
| the procedure name should be qualified with the class namespace |
| like "\fIclassName\fB::\fIproc\fR". Class procs execute in the |
| class context, and therefore have automatic access to all "common" |
| data members. However, they cannot access object-specific "variables", |
| since they are invoked without reference to any specific object. |
| They are usually used to perform generic operations which affect |
| all objects belonging to the class. |
| .PP |
| Each of the elements in a class can be declared "public", "protected" |
| or "private". Public elements can be accessed by the class, by |
| derived classes (other classes that inherit this class), and by |
| external clients that use the class. Protected elements can be |
| accessed by the class, and by derived classes. Private elements |
| are only accessible in the class where they are defined. |
| .PP |
| The "public" elements within a class define its interface to the |
| external world. Public methods define the operations that can |
| be used to manipulate an object. Public variables are recognized |
| as configuration options by the "configure" and "cget" methods |
| that are built into each class. The public interface says |
| \fIwhat\fR an object will do but not \fIhow\fR it will do it. |
| Protected and private members, along with the bodies of class |
| methods and procs, provide the implementation details. Insulating |
| the application developer from these details leaves the class designer |
| free to change them at any time, without warning, and without affecting |
| programs that rely on the class. It is precisely this encapsulation |
| that makes object-oriented programs easier to understand and maintain. |
| .PP |
| The fact that \fB[incr\ Tcl]\fR objects look like Tk widgets is |
| no accident. \fB[incr\ Tcl]\fR was designed this way, to blend |
| naturally into a Tcl/Tk application. But \fB[incr\ Tcl]\fR |
| extends the Tk paradigm from being merely object-based to being |
| fully object-oriented. An object-oriented system supports |
| inheritance, allowing classes to share common behaviors by |
| inheriting them from an ancestor or base class. Having a base |
| class as a common abstraction allows a programmer to treat |
| related classes in a similar manner. For example, a toaster |
| and a blender perform different (specialized) functions, but |
| both share the abstraction of being appliances. By abstracting |
| common behaviors into a base class, code can be \fIshared\fR rather |
| than \fIcopied\fR. The resulting application is easier to |
| understand and maintain, and derived classes (e.g., specialized |
| appliances) can be added or removed more easily. |
| .PP |
| This description was merely a brief overview of object-oriented |
| programming and \fB[incr\ Tcl]\fR. A more tutorial introduction is |
| presented in the paper included with this distribution. See the |
| \fBclass\fR command for more details on creating and using classes. |
| |
| .SH NAMESPACES |
| .PP |
| \fB[incr\ Tcl]\fR now includes a complete namespace facility. |
| A namespace is a collection of commands and global variables that |
| is kept apart from the usual global scope. This allows Tcl code |
| libraries to be packaged in a well-defined manner, and prevents |
| unwanted interactions with other libraries. A namespace can also |
| have child namespaces within it, so one library can contain its |
| own private copy of many other libraries. A namespace can also |
| be used to wrap up a group of related classes. The global scope |
| (named "\fC::\fR") is the root namespace for an interpreter; all |
| other namespaces are contained within it. |
| .PP |
| See the \fBnamespace\fR command for details on creating and |
| using namespaces. |
| |
| .SH MEGA-WIDGETS |
| .PP |
| Mega-widgets are high-level widgets that are constructed using |
| Tk widgets as component parts, usually without any C code. A |
| fileselectionbox, for example, may have a few listboxes, some |
| entry widgets and some control buttons. These individual widgets |
| are put together in a way that makes them act like one big |
| widget. |
| .PP |
| \fB[incr\ Tk]\fR is a framework for building mega-widgets. It |
| uses \fB[incr\ Tcl]\fR to support the object paradigm, and adds |
| base classes which provide default widget behaviors. See the |
| \fBitk\fR man page for more details. |
| .PP |
| \fB[incr\ Widgets]\fR is a library of mega-widgets built using |
| \fB[incr\ Tk]\fR. It contains more than 30 different widget |
| classes that can be used right out of the box to build Tcl/Tk |
| applications. Each widget class has its own man page describing |
| the features available. |
| |
| .SH KEYWORDS |
| class, object, object-oriented, namespace, mega-widget |