class.n

这是一个Linux下的集成开发环境

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'\" Copyright (c) 1993-1998  Lucent Technologies, Inc.
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'\" RCS: $Id: class.n,v 1.1 2003/02/05 10:53:53 mdejong Exp $
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.so man.macros
.TH class n "" itcl "[incr\ Tcl]"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
class \- create a class of objects
.SH SYNOPSIS
\fBclass \fIclassName\fR \fB{
.br
    \fBinherit \fIbaseClass\fR ?\fIbaseClass\fR...?
.br
    \fBconstructor \fIargs\fR ?\fIinit\fR? \fIbody\fR
.br
    \fBdestructor \fIbody\fR
.br
    \fBmethod \fIname\fR ?\fIargs\fR? ?\fIbody\fR?
.br
    \fBproc \fIname ?\fIargs\fR? ?\fIbody\fR?
.br
    \fBvariable \fIvarName\fR ?\fIinit\fR? ?\fIconfig\fR?
.br
    \fBcommon \fIvarName\fR ?\fIinit\fR?
.sp
    \fBpublic \fIcommand\fR ?\fIarg arg ...\fR?
.br
    \fBprotected \fIcommand\fR ?\fIarg arg ...\fR?
.br
    \fBprivate \fIcommand\fR ?\fIarg arg ...\fR?
.sp
    \fBset \fIvarName\fR ?\fIvalue\fR?
.br
    \fBarray \fIoption\fR ?\fIarg arg ...\fR?
.br
\fB}\fR
.sp
\fIclassName objName\fR ?\fIarg arg ...\fR?
.sp
\fIobjName method\fR ?\fIarg arg ...\fR?
.sp
\fIclassName::proc ?\fIarg arg ...\fR?
.BE

.SH DESCRIPTION
.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.
The class itself is a namespace which contains things common to all
objects.  Each object has its own unique bundle of data which contains
instances of the "variables" defined in the class definition.  Each
object also has a built-in variable named "this", which contains the
name of the object.  Classes can also have "common" data members that
are shared by all objects in a class.
.PP
Two types of functions can be included in the class definition.
"Methods" are functions which operate on a specific object, and
therefore have access to both "variables" and "common" data members.
"Procs" are ordinary procedures in the class namespace, and only
have access to "common" data members.
.PP
If the body of any method or proc starts with "\fB@\fR", it is treated
as the symbolic name for a C procedure.  Otherwise, it is treated as
a Tcl code script.  See below for details on registering and using
C procedures.
.PP
A class can only be defined once, although the bodies of class
methods and procs can be defined again and again for interactive
debugging.  See the \fBbody\fR and \fBconfigbody\fR commands for
details.
.PP
Each namespace can have its own collection of objects and classes.
The list of classes available in the current context can be queried
using the "\fBitcl::find classes\fR" command, and the list of objects,
with the "\fBitcl::find objects\fR" command.
.PP
A class can be deleted using the "\fBdelete class\fR" command.
Individual objects can be deleted using the "\fBdelete object\fR"
command.

.SH CLASS DEFINITIONS
.TP
\fBclass \fIclassName definition\fR
Provides the definition for a class named \fIclassName\fR.  If
the class \fIclassName\fR already exists, or if a command called
\fIclassName\fR exists in the current namespace context, this
command returns an error.  If the class definition is successfully
parsed, \fIclassName\fR becomes a command in the current context,
handling the creation of objects for this class.
.PP
The class \fIdefinition\fR is evaluated as a series of Tcl
statements that define elements within the class.  The following
class definition commands are recognized:
.RS
.TP
\fBinherit \fIbaseClass\fR ?\fIbaseClass\fR...?
Causes the current class to inherit characteristics from one or
more base classes.  Classes must have been defined by a previous
\fBclass\fR command, or must be available to the auto-loading
facility (see "AUTO-LOADING" below).  A single class definition
can contain no more than one \fBinherit\fR command.
.sp
The order of \fIbaseClass\fR names in the \fBinherit\fR list
affects the name resolution for class members.  When the same
member name appears in two or more base classes, the base class
that appears first in the \fBinherit\fR list takes precedence.
For example, if classes "Foo" and "Bar" both contain the member
"x", and if another class has the "\fBinherit\fR" statement:
.CS
inherit Foo Bar
.CE
then the name "x" means "Foo::x".  Other inherited members named
"x" must be referenced with their explicit name, like "Bar::x".
.TP
\fBconstructor \fIargs\fR ?\fIinit\fR? \fIbody\fR
Declares the \fIargs\fR argument list and \fIbody\fR used for
the constructor, which is automatically invoked whenever an
object is created.
.sp
Before the \fIbody\fR is executed, the
optional \fIinit\fR statement is used to invoke any base class
constructors that require arguments.  Variables in the \fIargs\fR
specification can be accessed in the \fIinit\fR code fragment,
and passed to base class constructors.  After evaluating the
\fIinit\fR statement, any base class constructors that have
not been executed are invoked automatically without arguments.
This ensures that all base classes are fully constructed before
the constructor \fIbody\fR is executed.  By default, this
scheme causes constructors to be invoked in order from least-
to most-specific.  This is exactly the opposite of the order
that classes are reported by the \fBinfo heritage\fR command.
.sp
If construction is successful, the constructor always returns
the object name\-regardless of how the \fIbody\fR is defined\-and
the object name becomes a command in the current namespace context.
If construction fails, an error message is returned.
.TP
\fBdestructor \fIbody\fR
Declares the \fIbody\fR used for the destructor, which is automatically
invoked when an object is deleted.  If the destructor is successful,
the object data is destroyed and the object name is removed as a command
from the interpreter.  If destruction fails, an error message is returned
and the object remains.
.sp
When an object is destroyed, all destructors in its class hierarchy
are invoked in order from most- to least-specific.  This is the
order that the classes are reported by the "\fBinfo heritage\fR"
command, and it is exactly the opposite of the default constructor
order.
.TP
\fBmethod \fIname\fR ?\fIargs\fR? ?\fIbody\fR?
Declares a method called \fIname\fR.  When the method \fIbody\fR is
executed, it will have automatic access to object-specific variables
and common data members.
.sp
If the \fIargs\fR list is specified, it establishes the usage
information for this method.  The \fBbody\fR command can be used
to redefine the method body, but the \fIargs\fR list must match
this specification.
.sp
Within the body of another class method, a method can be invoked
like any other command\-simply by using its name.  Outside of the
class context, the method name must be prefaced an object name,
which provides the context for the data that it manipulates.
Methods in a base class that are redefined in the current class,
or hidden by another base class, can be qualified using the
"\fIclassName\fR::\fImethod\fR" syntax.
.TP
\fBproc \fIname\fR ?\fIargs\fR? ?\fIbody\fR?
Declares a proc called \fIname\fR.  A proc is an ordinary procedure
within the class namespace.  Unlike a method, a proc is invoked
without referring to a specific object.  When the proc \fIbody\fR is
executed, it will have automatic access only to common data members.
.sp
If the \fIargs\fR list is specified, it establishes the usage
information for this proc.  The \fBbody\fR command can be used
to redefine the proc body, but the \fIargs\fR list must match
this specification.
.sp
Within the body of another class method or proc, a proc can be
invoked like any other command\-simply by using its name.
In any other namespace context, the proc is invoked using a
qualified name like "\fIclassName\fB::\fIproc\fR".  Procs in
a base class that are redefined in the current class, or hidden
by another base class, can also be accessed via their qualified
name.
.TP
\fBvariable \fIvarName\fR ?\fIinit\fR? ?\fIconfig\fR?
Defines an object-specific variable named \fIvarName\fR.  All
object-specific variables are automatically available in class
methods.  They need not be declared with anything like the
\fBglobal\fR command.
.sp
If the optional \fIinit\fR string is specified, it is used as the
initial value of the variable when a new object is created.
Initialization forces the variable to be a simple scalar
value; uninitialized variables, on the other hand, can be set
within the constructor and used as arrays.
.sp
The optional \fIconfig\fR script is only allowed for public variables.
If specified, this code fragment is executed whenever a public
variable is modified by the built-in "configure" method.  The
\fIconfig\fR script can also be specified outside of the class
definition using the \fBconfigbody\fR command.
.TP
\fBcommon \fIvarName\fR ?\fIinit\fR?
Declares a common variable named \fIvarName\fR.  Common variables
reside in the class namespace and are shared by all objects belonging
to the class.  They are just like global variables, except that
they need not be declared with the usual \fBglobal\fR command.
They are automatically visible in all class methods and procs.
.sp
If the optional \fIinit\fR string is specified, it is used as the
initial value of the variable.  Initialization forces the variable
to be a simple scalar value; uninitialized variables, on the other
hand, can be set with subsequent \fBset\fR and \fBarray\fR commands
and used as arrays.
.sp
Once a common data member has been defined, it can be set using
\fBset\fR and \fBarray\fR commands within the class definition.
This allows common data members to be initialized as arrays.
For example:
.CS
class Foo {
    common boolean
    set boolean(true) 1
    set boolean(false) 0
}
.CE
Note that if common data members are initialized within the
constructor, they get initialized again and again whenever new
objects are created.
.TP
\fBpublic \fIcommand\fR ?\fIarg arg ...\fR?
.TP
\fBprotected \fIcommand\fR ?\fIarg arg ...\fR?
.TP
\fBprivate \fIcommand\fR ?\fIarg arg ...\fR?
These commands are used to set the protection level for class
members that are created when \fIcommand\fR is evaluated.