trunk/Examples/tcl/class/index.html - third_party/swig - Git at Google

 <html>
 <head>
 <title>SWIG:Examples:tcl:class</title>
 </head>

 <body bgcolor="#ffffff">


 <tt>SWIG/Examples/tcl/class/</tt>
 <hr>

 <H2>Wrapping a simple C++ class</H2>

 <p>
 This example illustrates the most primitive form of C++ class wrapping performed
 by SWIG.  In this case, C++ classes are simply transformed into a collection of
 C-style functions that provide access to class members.

 <h2>The C++ Code</h2>

 Suppose you have some C++ classes described by the following (and admittedly lame)
 header file:

 <blockquote>
 <pre>
 /* File : example.h */

 class Shape {
 public:
   Shape() {
     nshapes++;
   }
   virtual ~Shape() {
     nshapes--;
   };
   double  x, y;
   void    move(double dx, double dy);
   virtual double area() = 0;
   virtual double perimeter() = 0;
   static  int nshapes;
 };

 class Circle : public Shape {
 private:
   double radius;
 public:
   Circle(double r) : radius(r) { };
   virtual double area();
   virtual double perimeter();
 };

 class Square : public Shape {
 private:
   double width;
 public:
   Square(double w) : width(w) { };
   virtual double area();
   virtual double perimeter();
 };
 </pre>
 </blockquote>

 <h2>The SWIG interface</h2>

 A simple SWIG interface for this can be built by simply grabbing the header file
 like this:

 <blockquote>
 <pre>
 /* File : example.i */
 %module example

 %{
 #include "example.h"
 %}

 /* Let's just grab the original header file here */
 %include "example.h"
 </pre>
 </blockquote>

 Note: when creating a C++ extension, you must run SWIG with the <tt>-c++</tt> option like this:
 <blockquote>
 <pre>
 % swig -c++ -tcl example.i
 </pre>
 </blockquote>

 <h2>Some sample Tcl scripts</h2>

 SWIG performs two forms of C++ wrapping-- a low level interface and a high level widget-like interface.
 <ul>
 <li>
 Click <a href="example1.tcl">here</a> to see a script that calls the C++ functions using the
 low-level interface.
 <li>
 Click <a href="example2.tcl">here</a> to see a the same script written with the high-level
 interface.
 </ul>

 <h2>Key points</h2>

 <ul>
 <li>The low-level C++ interface works like this:
 <p>
 <ul>
 <li>To create a new object, you call a constructor like this:

 <blockquote>
 <pre>
 set c [new_Circle 10.0]
 </pre>
 </blockquote>

 <p>
 <li>To access member data, a pair of accessor functions are used.
 For example:

 <blockquote>
 <pre>
 Shape_x_set $c 15        ;# Set member data
 set x [Shape_x_get $c]   ;# Get member data
 </pre>
 </blockquote>

 Note: when accessing member data, the name of the base class must
 be used such as <tt>Shape_x_get</tt>

 <p>
 <li>To invoke a member function, you simply do this

 <blockquote>
 <pre>
 puts "The area is [Shape_area $c]"
 </pre>
 </blockquote>

 <p>
 <li>Type checking knows about the inheritance structure of C++. For example:

 <blockquote>
 <pre>
 Shape_area $c       # Works (c is a Shape)
 Circle_area $c      # Works (c is a Circle)
 Square_area $c      # Fails (c is definitely not a Square)
 </pre>
 </blockquote>

 <p>
 <li>To invoke a destructor, simply do this

 <blockquote>
 <pre>
 delete_Shape $c     # Deletes a shape
 </pre>
 </blockquote>

 <p>
 <li>Static member variables are wrapped as C global variables.  For example:

 <blockquote>
 <pre>
 set n $Shape_nshapes    # Get a static data member
 set Shapes_nshapes 13   # Set a static data member
 </pre>
 </blockquote>

 </ul>

 <p>
 <li>The high-level interface works like a Tk widget

 <p>
 <ul>
 <li>To create a new object, you call a constructor like this:

 <blockquote>
 <pre>
 Circle c 10      # c becomes a name for the Circle object
 </pre>
 </blockquote>

 <p>
 <li>To access member data, use cget and configure methods.
 For example:

 <blockquote>
 <pre>
 c configure -x 15        ;# Set member data
 set x [c cget -x]        ;# Get member data
 </pre>
 </blockquote>

 <p>
 <li>To invoke a member function, you simply do this

 <blockquote>
 <pre>
 puts "The area is [c area]"
 </pre>
 </blockquote>

 <p>
 <li>To invoke a destructor, simply destroy the object name like this:

 <blockquote>
 <pre>
 rename c ""         # c goes away
 </pre>
 </blockquote>

 <p>
 <li>Static member variables are wrapped as C global variables.  For example:

 <blockquote>
 <pre>
 set n $Shape_nshapes    # Get a static data member
 set Shapes_nshapes 13   # Set a static data member
 </pre>
 </blockquote>

 </ul>
 </ul>

 <h2>General Comments</h2>

 <ul>
 <li>The low-level function interface is much faster than the high-level interface.
 In fact, all the higher level interface does is call functions in the low-level interface.

 <p>
 <li>SWIG *does* know how to properly perform upcasting of objects in an inheritance
 hierarchy (including multiple inheritance).  Therefore it is perfectly safe to pass
 an object of a derived class to any function involving a base class.

 <p>
 <li>A wide variety of C++ features are not currently supported by SWIG.  Here is the
 short and incomplete list:

 <p>
 <ul>
 <li>Overloaded methods and functions.  SWIG wrappers don't know how to resolve name
 conflicts so you must give an alternative name to any overloaded method name using the
 %name directive like this:

 <blockquote>
 <pre>
 void foo(int a);
 %name(foo2) void foo(double a, double b);
 </pre>
 </blockquote>

 <p>
 <li>Overloaded operators.  Not supported at all. The only workaround for this is
 to write a helper function. For example:

 <blockquote>
 <pre>
 %inline %{
     Vector *vector_add(Vector *a, Vector *b) {
           ... whatever ...
     }
 %}
 </pre>
 </blockquote>

 <p>
 <li>Namespaces.  Not supported at all. Won't be supported until SWIG2.0 (if at all).

 </ul>

 <hr>
 </body>
 </html>
	<html>
	<head>
	<title>SWIG:Examples:tcl:class</title>
	</head>

	<body bgcolor="#ffffff">


	<tt>SWIG/Examples/tcl/class/</tt>
	<hr>

	<H2>Wrapping a simple C++ class</H2>

	<p>
	This example illustrates the most primitive form of C++ class wrapping performed
	by SWIG. In this case, C++ classes are simply transformed into a collection of
	C-style functions that provide access to class members.

	<h2>The C++ Code</h2>

	Suppose you have some C++ classes described by the following (and admittedly lame)
	header file:

	<blockquote>
	<pre>
	/* File : example.h */

	class Shape {
	public:
	Shape() {
	nshapes++;
	}
	virtual ~Shape() {
	nshapes--;
	};
	double x, y;
	void move(double dx, double dy);
	virtual double area() = 0;
	virtual double perimeter() = 0;
	static int nshapes;
	};

	class Circle : public Shape {
	private:
	double radius;
	public:
	Circle(double r) : radius(r) { };
	virtual double area();
	virtual double perimeter();
	};

	class Square : public Shape {
	private:
	double width;
	public:
	Square(double w) : width(w) { };
	virtual double area();
	virtual double perimeter();
	};
	</pre>
	</blockquote>

	<h2>The SWIG interface</h2>

	A simple SWIG interface for this can be built by simply grabbing the header file
	like this:

	<blockquote>
	<pre>
	/* File : example.i */
	%module example

	%{
	#include "example.h"
	%}

	/* Let's just grab the original header file here */
	%include "example.h"
	</pre>
	</blockquote>

	Note: when creating a C++ extension, you must run SWIG with the <tt>-c++</tt> option like this:
	<blockquote>
	<pre>
	% swig -c++ -tcl example.i
	</pre>
	</blockquote>

	<h2>Some sample Tcl scripts</h2>

	SWIG performs two forms of C++ wrapping-- a low level interface and a high level widget-like interface.
	<ul>
	<li>
	Click <a href="example1.tcl">here</a> to see a script that calls the C++ functions using the
	low-level interface.
	<li>
	Click <a href="example2.tcl">here</a> to see a the same script written with the high-level
	interface.
	</ul>

	<h2>Key points</h2>

	<ul>
	<li>The low-level C++ interface works like this:
	<p>
	<ul>
	<li>To create a new object, you call a constructor like this:

	<blockquote>
	<pre>
	set c [new_Circle 10.0]
	</pre>
	</blockquote>

	<p>
	<li>To access member data, a pair of accessor functions are used.
	For example:

	<blockquote>
	<pre>
	Shape_x_set $c 15 ;# Set member data
	set x [Shape_x_get $c] ;# Get member data
	</pre>
	</blockquote>

	Note: when accessing member data, the name of the base class must
	be used such as <tt>Shape_x_get</tt>

	<p>
	<li>To invoke a member function, you simply do this

	<blockquote>
	<pre>
	puts "The area is [Shape_area $c]"
	</pre>
	</blockquote>

	<p>
	<li>Type checking knows about the inheritance structure of C++. For example:

	<blockquote>
	<pre>
	Shape_area $c # Works (c is a Shape)
	Circle_area $c # Works (c is a Circle)
	Square_area $c # Fails (c is definitely not a Square)
	</pre>
	</blockquote>

	<p>
	<li>To invoke a destructor, simply do this

	<blockquote>
	<pre>
	delete_Shape $c # Deletes a shape
	</pre>
	</blockquote>

	<p>
	<li>Static member variables are wrapped as C global variables. For example:

	<blockquote>
	<pre>
	set n $Shape_nshapes # Get a static data member
	set Shapes_nshapes 13 # Set a static data member
	</pre>
	</blockquote>

	</ul>

	<p>
	<li>The high-level interface works like a Tk widget

	<p>
	<ul>
	<li>To create a new object, you call a constructor like this:

	<blockquote>
	<pre>
	Circle c 10 # c becomes a name for the Circle object
	</pre>
	</blockquote>

	<p>
	<li>To access member data, use cget and configure methods.
	For example:

	<blockquote>
	<pre>
	c configure -x 15 ;# Set member data
	set x [c cget -x] ;# Get member data
	</pre>
	</blockquote>

	<p>
	<li>To invoke a member function, you simply do this

	<blockquote>
	<pre>
	puts "The area is [c area]"
	</pre>
	</blockquote>

	<p>
	<li>To invoke a destructor, simply destroy the object name like this:

	<blockquote>
	<pre>
	rename c "" # c goes away
	</pre>
	</blockquote>

	<p>
	<li>Static member variables are wrapped as C global variables. For example:

	<blockquote>
	<pre>
	set n $Shape_nshapes # Get a static data member
	set Shapes_nshapes 13 # Set a static data member
	</pre>
	</blockquote>

	</ul>
	</ul>

	<h2>General Comments</h2>

	<ul>
	<li>The low-level function interface is much faster than the high-level interface.
	In fact, all the higher level interface does is call functions in the low-level interface.

	<p>
	<li>SWIG does know how to properly perform upcasting of objects in an inheritance
	hierarchy (including multiple inheritance). Therefore it is perfectly safe to pass
	an object of a derived class to any function involving a base class.

	<p>
	<li>A wide variety of C++ features are not currently supported by SWIG. Here is the
	short and incomplete list:

	<p>
	<ul>
	<li>Overloaded methods and functions. SWIG wrappers don't know how to resolve name
	conflicts so you must give an alternative name to any overloaded method name using the
	%name directive like this:

	<blockquote>
	<pre>
	void foo(int a);
	%name(foo2) void foo(double a, double b);
	</pre>
	</blockquote>

	<p>
	<li>Overloaded operators. Not supported at all. The only workaround for this is
	to write a helper function. For example:

	<blockquote>
	<pre>
	%inline %{
	Vector vector_add(Vector a, Vector *b) {
	... whatever ...
	}
	%}
	</pre>
	</blockquote>

	<p>
	<li>Namespaces. Not supported at all. Won't be supported until SWIG2.0 (if at all).

	</ul>

	<hr>
	</body>
	</html>