From: <gg...@us...> - 2007-05-03 11:52:47
|
Revision: 9762 http://swig.svn.sourceforge.net/swig/?rev=9762&view=rev Author: gga73 Date: 2007-05-03 04:52:45 -0700 (Thu, 03 May 2007) Log Message: ----------- Documented the two ways that support for ruby blocks can be added to classes' constructors and methods. Modified Paths: -------------- trunk/Doc/Manual/Ruby.html Modified: trunk/Doc/Manual/Ruby.html =================================================================== --- trunk/Doc/Manual/Ruby.html 2007-05-03 10:48:17 UTC (rev 9761) +++ trunk/Doc/Manual/Ruby.html 2007-05-03 11:52:45 UTC (rev 9762) @@ -1,634 +1,454 @@ <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> + <title>SWIG and Ruby</title> - - - - <title>SWIG and Ruby</title> <link rel="stylesheet" type="text/css" href="style.css"> + </head> <body style="background-color: rgb(255, 255, 255);"> - <h1><a name="Ruby"></a>30 SWIG and Ruby</h1> - <!-- INDEX --> <div class="sectiontoc"> <ul> - <li><a href="#Ruby_nn2">Preliminaries</a> - <ul> - <li><a href="#Ruby_nn3">Running SWIG</a> </li> - <li><a href="#Ruby_nn4">Getting the right header files</a> </li> - <li><a href="#Ruby_nn5">Compiling a dynamic module</a> </li> - <li><a href="#Ruby_nn6">Using your module</a> </li> - <li><a href="#Ruby_nn7">Static linking</a> </li> - <li><a href="#Ruby_nn8">Compilation of C++ extensions</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn9">Building Ruby Extensions under Windows 95/NT</a> - <ul> - <li><a href="#Ruby_nn10">Running SWIG from Developer Studio</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn11">The Ruby-to-C/C++ Mapping</a> - <ul> - <li><a href="#Ruby_nn12">Modules</a> </li> - <li><a href="#Ruby_nn13">Functions</a> </li> - <li><a href="#Ruby_nn14">Variable Linking</a> </li> - <li><a href="#Ruby_nn15">Constants</a> </li> - <li><a href="#Ruby_nn16">Pointers</a> </li> - <li><a href="#Ruby_nn17">Structures</a> </li> - <li><a href="#Ruby_nn18">C++ classes</a> </li> - <li><a href="#Ruby_nn19">C++ Inheritance</a> </li> - <li><a href="#Ruby_nn20">C++ Overloaded Functions</a> </li> - <li><a href="#Ruby_nn21">C++ Operators</a> </li> - <li><a href="#Ruby_nn22">C++ namespaces</a> </li> - <li><a href="#Ruby_nn23">C++ templates</a></li> + <ul> - <li><a href="#Ruby_nn23_1">C++ Standard Template Library (STL)</a></li> - </ul> + <li><a href="#Ruby_nn23_1">C++ Standard +Template Library (STL)</a></li> + </ul> + <li><a href="#Ruby_nn24">C++ Smart Pointers</a> </li> - <li><a href="#Ruby_nn25">Cross-Language Polymorphism</a> - <ul> - <li><a href="#Ruby_nn26">Exception Unrolling</a> </li> - - </ul> - </li> - - </ul> - </li> - <li><a href="#Ruby_nn27">Naming</a> - <ul> - <li><a href="#Ruby_nn28">Defining Aliases</a> </li> - <li><a href="#Ruby_nn29">Predicate Methods</a> </li> - <li><a href="#Ruby_nn30">Bang Methods</a> </li> - <li><a href="#Ruby_nn31">Getters and Setters</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn32">Input and output -parameters</a> </li> +parameters</a></li> - <li><a href="#Ruby_nn33">Exception handling </a> - <ul> - <li><a href="#Ruby_nn34">Using the %exception -directive </a> </li> +directive</a> + </li> + <li><a href="Ruby.html#Ruby_nn34_2">Handling +Ruby Blocks</a></li> <li><a href="#Ruby_nn35">Raising exceptions </a> </li> - <li><a href="#Ruby_nn36">Exception classes </a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn37">Typemaps</a> - <ul> - <li><a href="#Ruby_nn38">What is a typemap?</a> </li> - <li><a href="#Ruby_nn39">Ruby typemaps</a> </li> - <li><a href="#Ruby_nn40">Typemap variables</a> </li> - <li><a href="#Ruby_nn41">Useful Functions</a> - <ul> - <li><a href="#Ruby_nn42">C Datatypes to Ruby Objects</a> </li> - <li><a href="#Ruby_nn43">Ruby Objects to C Datatypes</a> </li> - <li><a href="#Ruby_nn44">Macros for VALUE</a> </li> - <li><a href="#Ruby_nn45">Exceptions</a> </li> - <li><a href="#Ruby_nn46">Iterators</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn47">Typemap Examples</a> </li> - <li><a href="#Ruby_nn48">Converting a Ruby array to a char **</a> </li> - <li><a href="#Ruby_nn49">Collecting arguments in a hash</a> </li> - <li><a href="#Ruby_nn50">Pointer handling</a> - <ul> - <li><a href="#Ruby_nn51">Ruby Datatype Wrapping</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn52">Example: STL Vector to Ruby Array</a></li> - - </ul> - </li> - <li><a href="#Ruby_nn65">Docstring Features</a> - <ul> - <li><a href="#Ruby_nn66">Module -docstring</a> - </li> +docstring</a> </li> - <li><a href="#Ruby_nn67">%feature("autodoc")</a> - <ul> - <li><a href="#Ruby_nn68">%feature("autodoc", -"0")</a> - </li> +"0")</a> </li> - <li><a href="#Ruby_nn69">%feature("autodoc", -"1")</a> - </li> +"1")</a> </li> - <li><a href="#Ruby_nn70">%feature("autodoc", -"2")</a> - </li> +"2")</a> </li> - <li><a href="#Ruby_nn71">%feature("autodoc", -"3")</a> - </li> +"3")</a> </li> - <li><a href="#Ruby_nn72">%feature("autodoc", -"docstring")</a> - </li> +"docstring")</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn73">%feature("docstring")</a></li> - - </ul> - </li> - <li><a href="#Ruby_nn53">Advanced Topics</a> - <ul> - <li><a href="#Ruby_nn54">Operator overloading</a> </li> - <li><a href="#Ruby_nn55">Creating Multi-Module Packages</a> </li> - <li><a href="#Ruby_nn56">Specifying Mixin Modules</a> </li> - - </ul> - </li> - <li><a href="#Ruby_nn57">Memory Management</a> - <ul> - <li><a href="#Ruby_nn58">Mark and Sweep Garbage Collector </a> </li> - <li><a href="#Ruby_nn59">Object Ownership</a> </li> - <li><a href="#Ruby_nn60">Object Tracking</a> </li> - <li><a href="#Ruby_nn61">Mark Functions</a> </li> - <li><a href="#Ruby_nn62">Free Functions</a></li> - <li><a href="#Ruby_nn63">Embedded Ruby and the C++ Stack</a></li> + <li><a href="#Ruby_nn63">Embedded Ruby and the +C++ Stack</a></li> - - </ul> - </li> - </ul> - </div> - <!-- INDEX --> <p>This chapter describes SWIG's support of Ruby.</p> - <h2><a name="Ruby_nn2"></a>30.1 Preliminaries</h2> - <p> SWIG 1.3 is known to work with Ruby versions 1.6 and later. Given the choice, you should use the latest stable version of Ruby. You should also determine if your system supports shared libraries and dynamic loading. SWIG will work with or without dynamic loading, but the compilation process will vary. </p> - <p>This chapter covers most SWIG features, but in less depth than is found in earlier chapters. At the very least, make sure you also read the "<a href="SWIG.html#SWIG">SWIG Basics</a>" chapter. It is also assumed that the reader has a basic understanding of Ruby. </p> - <h3><a name="Ruby_nn3"></a>30.1.1 Running SWIG</h3> - <p> To build a Ruby module, run SWIG using the <tt>-ruby</tt> option:</p> - <div class="code shell"> <pre>$ <b>swig -ruby example.i</b> </pre> - </div> - <p> If building a C++ extension, add the <tt>-c++</tt> option: </p> - <div class="code shell"> <pre>$ <b>swig -c++ -ruby example.i</b> </pre> - </div> - <p> This creates a file <tt>example_wrap.c</tt> (<tt>example_wrap.cxx</tt> if compiling a C++ extension) that contains all of the code needed to build a Ruby extension module. To finish building the module, you need to compile this file and link it with the rest of your program. </p> - <h3><a name="Ruby_nn4"></a>30.1.2 Getting the right header files</h3> - <p> In order to compile the wrapper code, the compiler needs the <tt>ruby.h</tt> header file. This file is usually contained in a directory such as </p> - <div class="code shell diagram"> <pre>/usr/local/lib/ruby/1.6/i686-linux/ruby.h<br></pre> - </div> - <p> The exact location may vary on your machine, but the above location is typical. If you are not entirely sure where Ruby is installed, you can run Ruby to find out. For example: </p> - <div class="code shell"> <pre>$ <b>ruby -e 'puts $:.join("\n")'</b><br>/usr/local/lib/ruby/site_ruby/1.6 /usr/local/lib/ruby/site_ruby/1.6/i686-linux<br>/usr/local/lib/ruby/site_ruby /usr/local/lib/ruby/1.6 /usr/local/lib/ruby/1.6/i686-linux .<br> </pre> - </div> - <h3><a name="Ruby_nn5"></a>30.1.3 Compiling a dynamic module</h3> - <p> Ruby extension modules are typically compiled into shared libraries that the interpreter loads dynamically at runtime. Since the exact commands for doing this vary from platform to platform, your best bet is to follow the steps described in the <tt>README.EXT</tt> file from the Ruby distribution: </p> - <ol> - <li> - <p>Create a file called <tt>extconf.rb</tt> that looks like the following:</p> - - <div class="code targetlang"> - <pre>require 'mkmf'<br>create_makefile('example')<br></pre> - </div> - </li> - <li> - <p>Type the following to build the extension:</p> - - <div class="code shell"> - <pre>$ <b>ruby extconf.rb</b><br>$ <b>make</b><br>$ <b>make install</b> </pre> - </div> - </li> - </ol> - <p> Of course, there is the problem that mkmf does not work correctly on all platforms, e.g, HPUX. If you need to add your own make rules to the file that <tt>extconf.rb</tt> produces, you can add this: </p> - <div class="code targetlang"> <pre>open("Makefile", "a") { |mf|<br> puts <<EOM<br> # Your make rules go here<br> EOM<br>}<br></pre> - </div> - <p> to the end of the <tt>extconf.rb</tt> file. If for some reason you don't want to use the standard approach, you'll need to determine the correct compiler and linker flags for your build platform. For example, a typical sequence of commands for the Linux operating system would look something like this: </p> - <div class="code shell"> <pre>$ <b>swig -ruby example.i</b><br>$ <b>gcc -c example.c</b><br>$ <b>gcc -c example_wrap.c -I/usr/local/lib/ruby/1.6/i686-linux</b> <br>$ <b>gcc -shared example.o example_wrap.o -o example.so</b> </pre> - </div> - <p> For other platforms it may be necessary to compile with the <tt>-fPIC</tt> option to generate position-independent code. If in doubt, consult the manual pages for your compiler and linker to determine the correct set of options. You might also check the <a href="http://www.dabeaz.com/cgi-bin/wiki.pl">SWIG Wiki</a> for additional information. </p> - <p> <a name="n6"></a> </p> - <h3><a name="Ruby_nn6"></a>30.1.4 Using your module</h3> - <p> Ruby <i>module</i> names must be capitalized, but the convention for Ruby <i>feature</i> names is to use lowercase names. So, for example, the <b>Etc</b> extension module is imported by requiring the <b>etc</b> feature: </p> - <div class="code targetlang"> <pre># The feature name begins with a lowercase letter...<br>require 'etc'<br><br># ... but the module name begins with an uppercase letter<br>puts "Your login name: #{Etc.getlogin}"<br></pre> - </div> - <p> To stay consistent with this practice, you should always specify a <b>lowercase</b> module name with SWIG's <tt>%module</tt> directive. SWIG will automatically correct the resulting Ruby module name for your extension. So for example, a SWIG interface file that begins with: </p> - <div class="code"> <pre>%module example<br></pre> - </div> - <p> will result in an extension module using the feature name "example" and Ruby module name "Example". </p> - <h3><a name="Ruby_nn7"></a>30.1.5 Static linking</h3> - <p> An alternative approach to dynamic linking is to rebuild the Ruby interpreter with your extension module added to it. In the past, this approach was sometimes necessary due to limitations in dynamic @@ -636,32 +456,25 @@ improved greatly over the last few years and you should not consider this approach unless there is really no other option. </p> - <p>The usual procedure for adding a new module to Ruby involves finding the Ruby source, adding an entry to the <tt>ext/Setup</tt> file, adding your directory to the list of extensions in the file, and finally rebuilding Ruby. </p> - <p><a name="n8"></a></p> - <h3><a name="Ruby_nn8"></a>30.1.6 Compilation of C++ extensions</h3> - <p> On most machines, C++ extension modules should be linked using the C++ compiler. For example: </p> - <div class="code shell"> <pre>$ <b>swig -c++ -ruby example.i</b><br>$ <b>g++ -c example.cxx</b><br>$ <b>g++ -c example_wrap.cxx -I/usr/local/lib/ruby/1.6/i686-linux</b><br>$ <b>g++ -shared example.o example_wrap.o -o example.so</b> </pre> - </div> - <p> If you've written an <tt>extconf.rb</tt> script to automatically generate a <tt>Makefile</tt> for your C++ extension module, keep in mind that (as of this writing) Ruby still @@ -673,18 +486,14 @@ the C++ runtime libraries to the list of libraries linked into your extension, e.g. </p> - <div class="code targetlang"> <pre>require 'mkmf'<br>$libs = append_library($libs, "supc++")<br>create_makefile('example')<br></pre> - </div> - <h2><a name="Ruby_nn9"></a>30.2 Building Ruby Extensions under Windows 95/NT</h2> - <p> Building a SWIG extension to Ruby under Windows 95/NT is roughly similar to the process used with Unix. Normally, you will want to produce a DLL that can be loaded into the Ruby interpreter. For all @@ -692,15 +501,12 @@ script) will work with Windows as well; you should be able to build your code into a DLL by typing: </p> - <div class="code shell"> <pre>C:\swigtest> <b>ruby extconf.rb</b><br>C:\swigtest> <b>nmake</b><br>C:\swigtest> <b>nmake install</b> </pre> - </div> - <p> The remainder of this section covers the process of compiling SWIG-generated Ruby extensions with Microsoft Visual C++ 6 (i.e. within the Developer Studio IDE, instead of using the command line tools). In @@ -708,26 +514,20 @@ distribution to the Ruby package, as you will need the Ruby header files. </p> - <p><a name="n10"></a></p> - <h3><a name="Ruby_nn10"></a>30.2.1 Running SWIG from Developer Studio</h3> - <p> If you are developing your application within Microsoft developer studio, SWIG can be invoked as a custom build option. The process roughly follows these steps : </p> - <ul> - <li> Open up a new workspace and use the AppWizard to select a DLL project. </li> - <li> Add both the SWIG interface file (the .i file), any supporting C files, and the name of the wrapper file that will be created by SWIG (i.e. <tt>example_wrap.c</tt>). Note : If @@ -735,23 +535,18 @@ Don't worry if the wrapper file doesn't exist yet--Developer Studio will keep a reference to it around. </li> - <li> Select the SWIG interface file and go to the settings menu. Under settings, select the "Custom Build" option. </li> - <li> Enter "SWIG" in the description field. </li> - <li> Enter "<tt>swig -ruby -o $(ProjDir)\$(InputName)_wrap.c $(InputPath)</tt>" in the "Build command(s) field". You may have to include the path to swig.exe. </li> - <li> Enter "<tt>$(ProjDir)\$(InputName)_wrap.c</tt>" in the "Output files(s) field". </li> - <li> Next, select the settings for the entire project and go to the C/C++ tab and select the Preprocessor category. Add NT=1 to the Preprocessor definitions. This must be set else you will get @@ -759,7 +554,6 @@ else you may get runtime errors. Also add the include directories for your Ruby installation under "Additional include directories". </li> - <li> Next, select the settings for the entire project and go to the Link tab and select the General category. Set the name of the output file to match the name of your Ruby module (i.e.. example.dll). @@ -768,13 +562,10 @@ to add the path to the library under the Input tab - Additional library path. </li> - <li> Build your project. </li> - </ul> - <p> Now, assuming all went well, SWIG will be automatically invoked when you build your project. Any changes made to the interface file will result in SWIG being automatically invoked to produce a new @@ -782,60 +573,45 @@ Ruby and use the <tt>require</tt> command as normal. For example if you have this ruby file run.rb:</p> - <div class="code targetlang"> <pre># file: run.rb<br>require 'Example'<br><br># Call a c function<br>print "Foo = ", Example.Foo, "\n"<br></pre> - </div> - <p> Ensure the dll just built is in your path or current directory, then run the Ruby script from the DOS/Command prompt: </p> - <div class="code shell"> <pre>C:\swigtest> <b>ruby run.rb</b><br>Foo = 3.0<br></pre> - </div> - <h2><a name="Ruby_nn11"></a>30.3 The Ruby-to-C/C++ Mapping</h2> - <p> This section describes the basics of how SWIG maps C or C++ declarations in your SWIG interface files to Ruby constructs. </p> - <h3><a name="Ruby_nn12"></a>30.3.1 Modules</h3> - <p> The SWIG <tt>%module</tt> directive specifies the name of the Ruby module. If you specify: </p> - <div class="code"> <pre>%module example</pre> - </div> - <p> then everything is wrapped into a Ruby module named <tt>Example</tt> that is nested directly under the global module. You can specify a more deeply nested module by specifying the fully-qualified module name in quotes, e.g. </p> - <div class="code"> <pre>%module "foo::bar::spam"</pre> - </div> - <p> An alternate method of specifying a nested module name is to use the <span style="font-family: monospace;">-prefix</span> option on the SWIG command line. The prefix that you specify with this @@ -843,64 +619,48 @@ directive in your SWIG interface file. So for example, this declaration at the top of your SWIG interface file:<br> - </p> - <div class="code"> <pre>%module "foo::bar::spam"</pre> - </div> - <p> will result in a nested module name of <span style="font-family: monospace;">Foo::Bar::Spam</span>, but you can achieve the <span style="font-style: italic;">same</span> effect by specifying:<br> - </p> - <div class="code"> <pre>%module spam</pre> - </div> - <p> and then running SWIG with the <span style="font-family: monospace;">-prefix</span> command line option:<br> - </p> - <div class="code shell"> <pre>$ <b>swig -ruby -prefix "foo::bar::" example.i</b></pre> - </div> - <p> Starting with SWIG 1.3.20, you can also choose to wrap everything into the global module by specifying the <tt>-globalmodule</tt> option on the SWIG command line, i.e. </p> - <div class="code shell"> <pre>$ <b>swig -ruby -globalmodule example.i</b></pre> - </div> - <p> Note that this does not relieve you of the requirement of specifying the SWIG module name with the <tt>%module</tt> directive (or the <tt>-module</tt> command-line option) as described earlier. </p> - <p>When choosing a module name, do not use the same name as a built-in Ruby command or standard module name, as the results may be unpredictable. Similarly, if you're using the <tt>-globalmodule</tt> @@ -908,204 +668,152 @@ names of your constants, classes and methods don't conflict with any of Ruby's built-in names. </p> - <h3><a name="Ruby_nn13"></a>30.3.2 Functions</h3> - <p> Global functions are wrapped as Ruby module methods. For example, given the SWIG interface file <tt>example.i</tt>: </p> - <div class="code"> <pre>%module example<br><br>int fact(int n);<br></pre> - </div> - <p> and C source file <tt>example.c</tt>: </p> - <div class="code"> <pre>int fact(int n) {<br> if (n == 0)<br> return 1;<br> return (n * fact(n-1));<br>}<br></pre> - </div> - <p> SWIG will generate a method <i>fact</i> in the <i>Example</i> module that can be used like so: </p> - <div class="code targetlang"> <pre>$ <b>irb</b><br>irb(main):001:0> <b>require 'example'</b><br>true<br>irb(main):002:0> <b>Example.fact(4)</b><br>24<br></pre> - </div> - <h3><a name="Ruby_nn14"></a>30.3.3 Variable Linking</h3> - <p> C/C++ global variables are wrapped as a pair of singleton methods for the module: one to get the value of the global variable and one to set it. For example, the following SWIG interface file declares two global variables: </p> - <div class="code"> <pre>// SWIG interface file with global variables<br>%module example<br>...<br>%inline %{<br>extern int variable1;<br>extern double Variable2;<br>%}<br>...<br></pre> - </div> - <p> Now look at the Ruby interface:</p> - <div class="code targetlang"> <pre>$ <b>irb</b><br>irb(main):001:0> <b>require 'Example'</b><br>true<br>irb(main):002:0> <b>Example.variable1 = 2</b><br>2<br>irb(main):003:0> <b>Example.Variable2 = 4 * 10.3</b><br>41.2<br>irb(main):004:0> <b>Example.Variable2</b><br>41.2<br></pre> - </div> - <p> If you make an error in variable assignment, you will receive an error message. For example: </p> - <div class="code targetlang"> <pre>irb(main):005:0> <b>Example.Variable2 = "hello"</b><br>TypeError: no implicit conversion to float from string<br>from (irb):5:in `Variable2='<br>from (irb):5<br></pre> - </div> - <p> If a variable is declared as <tt>const</tt>, it is wrapped as a read-only variable. Attempts to modify its value will result in an error. </p> - <p>To make ordinary variables read-only, you can also use the <tt>%immutable</tt> directive. For example: </p> - <div class="code"> <pre>%immutable;<br>%inline %{<br>extern char *path;<br>%}<br>%mutable;<br></pre> - </div> - <p> The <tt>%immutable</tt> directive stays in effect until it is explicitly disabled using <tt>%mutable</tt>. </p> - <h3><a name="Ruby_nn15"></a>30.3.4 Constants</h3> - <p> C/C++ constants are wrapped as module constants initialized to the appropriate value. To create a constant, use <tt>#define</tt> or the <tt>%constant</tt> directive. For example: </p> - <div class="code"> <pre>#define PI 3.14159<br>#define VERSION "1.0"<br><br>%constant int FOO = 42;<br>%constant const char *path = "/usr/local";<br><br>const int BAR = 32;<br></pre> - </div> - <p> Remember to use the :: operator in Ruby to get at these constant values, e.g. </p> - <div class="code targetlang"> <pre>$ <b>irb</b><br>irb(main):001:0> <b>require 'Example'</b><br>true<br>irb(main):002:0> <b>Example::PI</b><br>3.14159<br></pre> - </div> - <h3><a name="Ruby_nn16"></a>30.3.5 Pointers</h3> - <p> "Opaque" pointers to arbitrary C/C++ types (i.e. types that aren't explicitly declared in your SWIG interface file) are wrapped as data objects. So, for example, consider a SWIG interface file containing only the declarations: </p> - <div class="code"> <pre>Foo *get_foo();<br>void set_foo(Foo *foo);<br></pre> - </div> - <p> For this case, the <i>get_foo()</i> method returns an instance of an internally generated Ruby class: </p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>foo = Example::get_foo()</b><br>#<SWIG::TYPE_p_Foo:0x402b1654><br></pre> - </div> - <p> A <tt>NULL</tt> pointer is always represented by the Ruby <tt>nil</tt> object. </p> - <h3><a name="Ruby_nn17"></a>30.3.6 Structures</h3> - <p> C/C++ structs are wrapped as Ruby classes, with accessor methods (i.e. "getters" and "setters") for all of the struct members. For example, this struct declaration: </p> - <div class="code"> <pre>struct Vector {<br> double x, y;<br>};<br></pre> - </div> - <p> gets wrapped as a <tt>Vector</tt> class, with Ruby instance methods <tt>x</tt>, <tt> x=</tt>, <tt>y</tt> and <tt>y=</tt>. These methods can be used to access structure data from Ruby as follows: </p> - <div class="code targetlang"> <pre>$ <b>irb</b><br>irb(main):001:0> <b>require 'Example'</b><br>true<br>irb(main):002:0> <b>f = Example::Vector.new</b><br>#<Example::Vector:0x4020b268><br>irb(main):003:0> <b>f.x = 10</b><br>nil<br>irb(main):004:0> <b>f.x</b><br>10.0<br></pre> - </div> - <p> Similar access is provided for unions and the public data members of C++ classes.</p> - <p><tt>const</tt> members of a structure are read-only. Data members can also be forced to be read-only using the <tt>%immutable</tt> directive (in C++, <tt>private</tt> may also be used). For example: </p> - <div class="code"> <pre>struct Foo {<br> ...<br> %immutable;<br> int x; /* Read-only members */<br> char *name;<br> %mutable;<br> ...<br>};<br></pre> - </div> - <p> When <tt>char *</tt> members of a structure are wrapped, the contents are assumed to be dynamically allocated using <tt>malloc</tt> or <tt>new</tt> (depending on whether or not SWIG is run @@ -1114,59 +822,44 @@ this is not the behavior you want, you will have to use a typemap (described shortly). </p> - <p>Array members are normally wrapped as read-only. For example, this code: </p> - <div class="code"> <pre>struct Foo {<br> int x[50];<br>};<br></pre> - </div> - <p> produces a single accessor function like this: </p> - <div class="code"> <pre>int *Foo_x_get(Foo *self) {<br> return self->x;<br>};<br></pre> - </div> - <p> If you want to set an array member, you will need to supply a "memberin" typemap described in the <a href="#ruby_cpp_smart_pointers">section on typemaps</a>. As a special case, SWIG does generate code to set array members of type <tt>char</tt> (allowing you to store a Ruby string in the structure). </p> - <p>When structure members are wrapped, they are handled as pointers. For example, </p> - <div class="code"> <pre>struct Foo {<br> ...<br>};<br><br>struct Bar {<br> Foo f;<br>};<br></pre> - </div> - <p> generates accessor functions such as this: </p> - <div class="code"> <pre>Foo *Bar_f_get(Bar *b) {<br> return &b->f;<br>}<br><br>void Bar_f_set(Bar *b, Foo *val) {<br> b->f = *val;<br>}<br></pre> - </div> - <h3><a name="Ruby_nn18"></a>30.3.7 C++ classes</h3> - <p> Like structs, C++ classes are wrapped by creating a new Ruby class of the same name with accessor methods for the public class member data. Additionally, public member functions for the class are @@ -1174,87 +867,64 @@ are wrapped as Ruby singleton methods. So, given the C++ class declaration: </p> - <div class="code"> <pre>class List {<br>public:<br> List();<br> ~List();<br> int search(char *item);<br> void insert(char *item);<br> void remove(char *item);<br> char *get(int n);<br> int length;<br> static void print(List *l);<br>};<br></pre> - </div> - <p> SWIG would create a <tt>List</tt> class with: </p> - <ul> - <li> instance methods <i>search</i>, <i>insert</i>, <i>remove</i>, and <i>get</i>; </li> - <li> instance methods <i>length</i> and <i>length=</i> (to get and set the value of the <i>length</i> data member); and, </li> - <li> a <i>print</i> singleton method for the class. </li> - </ul> - <p> In Ruby, these functions are used as follows: </p> - <div class="code targetlang"> <pre>require 'Example'<br><br>l = Example::List.new<br><br>l.insert("Ale")<br>l.insert("Stout")<br>l.insert("Lager")<br>Example.print(l)<br>l.length()<br>----- produces the following output <br>Lager<br>Stout<br>Ale<br>3<br></pre> - </div> - <h3><a name="Ruby_nn19"></a>30.3.8 C++ Inheritance</h3> - <p> The SWIG type-checker is fully aware of C++ inheritance. Therefore, if you have classes like this: </p> - <div class="code"> <pre>class Parent {<br> ...<br>};<br><br>class Child : public Parent {<br> ...<br>};<br></pre> - </div> - <p> those classes are wrapped into a hierarchy of Ruby classes that reflect the same inheritance structure. All of the usual Ruby utility methods work normally: </p> - <div class="code"> <pre>irb(main):001:0> <b>c = Child.new</b><br>#<Bar:0x4016efd4><br>irb(main):002:0> <b>c.instance_of? Child</b><br>true<br>irb(main):003:0> <b>b.instance_of? Parent</b><br>false<br>irb(main):004:0> <b>b.is_a? Child</b><br>true<br>irb(main):005:0> <b>b.is_a? Parent</b><br>true<br>irb(main):006:0> <b>Child < Parent</b><br>true<br>irb(main):007:0> <b>Child > Parent</b><br>false<br></pre> - </div> - <p> Furthermore, if you have a function like this: </p> - <div class="code"> <pre>void spam(Parent *f);<br></pre> - </div> - <p> then the function <tt>spam()</tt> accepts <tt>Parent</tt>* or a pointer to any class derived from <tt>Parent</tt>. </p> - <p>Until recently, the Ruby module for SWIG didn't support multiple inheritance, and this is still the default behavior. This doesn't mean that you can't wrap C++ classes which inherit from @@ -1263,14 +933,11 @@ additional base classes are ignored. As an example, consider a SWIG interface file with a declaration like this: </p> - <div class="code"> <pre>class Derived : public Base1, public Base2<br>{<br> ...<br>};<br></pre> - </div> - <p> For this case, the resulting Ruby class (<tt>Derived</tt>) will only consider <tt>Base1</tt> as its superclass. It won't inherit any of <tt>Base2</tt>'s member functions or @@ -1279,39 +946,30 @@ relationship would fail). When SWIG processes this interface file, you'll see a warning message like: </p> - <div class="code shell"> <pre>example.i:5: Warning(802): Warning for Derived: Base Base2 ignored.<br>Multiple inheritance is not supported in Ruby.<br></pre> - </div> - <p> Starting with SWIG 1.3.20, the Ruby module for SWIG provides limited support for multiple inheritance. Because the approach for dealing with multiple inheritance introduces some limitations, this is an optional feature that you can activate with the <tt>-minherit</tt> command-line option: </p> - <div class="code shell"> <pre>$ <b>swig -c++ -ruby -minherit example.i</b></pre> - </div> - <p> Using our previous example, if your SWIG interface file contains a declaration like this: </p> - <div class="code"> <pre>class Derived : public Base1, public Base2<br>{<br> ...<br>};<br></pre> - </div> - <p> and you run SWIG with the <tt>-minherit</tt> command-line option, then you will end up with a Ruby class <tt>Derived</tt> that appears to "inherit" the member data and functions from both <tt>Base1</tt> @@ -1322,238 +980,178 @@ modules that the actual instance methods for the classes are defined, i.e. </p> - <div class="code targetlang"> <pre>class Base1<br> module Impl<br> # Define Base1 methods here<br> end<br> include Impl<br>end<br><br>class Base2<br> module Impl<br> # Define Base2 methods here<br> end<br> include Impl<br>end<br><br>class Derived<br> module Impl<br> include Base1::Impl<br> include Base2::Impl<br> # Define Derived methods here<br> end<br> include Impl<br>end<br></pre> - </div> - <p> Observe that after the nested <tt>Impl</tt> module for a class is defined, it is mixed-in to the class itself. Also observe that the <tt>Derived::Impl</tt> module first mixes-in its base classes' <tt>Impl</tt> modules, thus "inheriting" all of their behavior. </p> - <p>The primary drawback is that, unlike the default mode of operation, neither <tt>Base1</tt> nor <tt>Base2</tt> is a true superclass of <tt>Derived</tt> anymore: </p> - <div class="code targetlang"> <pre>obj = Derived.new<br>obj.is_a? Base1 # this will return false...<br>obj.is_a? Base2 # ... and so will this<br></pre> - </div> - <p> In most cases, this is not a serious problem since objects of type <tt>Derived</tt> will otherwise behave as though they inherit from both <tt>Base1</tt> and <tt>Base2</tt> (i.e. they exhibit <a href="http://c2.com/cgi/wiki?DuckTyping">"Duck Typing"</a>). </p> - <h3><a name="Ruby_nn20"></a>30.3.9 C++ Overloaded Functions</h3> - <p> C++ overloaded functions, methods, and constructors are mostly supported by SWIG. For example, if you have two functions like this: </p> - <div class="code"> <pre>void foo(int);<br>void foo(char *c);<br></pre> - </div> - <p> You can use them in Ruby in a straightforward manner: </p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>foo(3)</b> # foo(int)<br>irb(main):002:0> <b>foo("Hello")</b> # foo(char *c)<br></pre> - </div> - <p>Similarly, if you have a class like this,</p> - <div class="code"> <pre>class Foo {<br>public:<br> Foo();<br> Foo(const Foo &);<br> ...<br>};<br></pre> - </div> - <p>you can write Ruby code like this:</p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>f = Foo.new</b> # Create a Foo<br>irb(main):002:0> <b>g = Foo.new(f)</b> # Copy f<br></pre> - </div> - <p> Overloading support is not quite as flexible as in C++. Sometimes there are methods that SWIG can't disambiguate. For example: </p> - <div class="code"> <pre>void spam(int);<br>void spam(short);<br></pre> - </div> - <p>or</p> - <div class="code"> <pre>void foo(Bar *b);<br>void foo(Bar &b);<br></pre> - </div> - <p> If declarations such as these appear, you will get a warning message like this: </p> - <div class="code shell"> <pre>example.i:12: Warning(509): Overloaded spam(short) is shadowed by spam(int)<br>at example.i:11.<br> </pre> - </div> - <p> To fix this, you either need to ignore or rename one of the methods. For example: </p> - <div class="code"> <pre>%rename(spam_short) spam(short);<br>...<br>void spam(int); <br>void spam(short); // Accessed as spam_short<br></pre> - </div> - <p>or</p> - <div class="code"> <pre>%ignore spam(short);<br>...<br>void spam(int); <br>void spam(short); // Ignored<br></pre> - </div> - <p> SWIG resolves overloaded functions and methods using a disambiguation scheme that ranks and sorts declarations according to a set of type-precedence rules. The order in which declarations appear in the input does not matter except in situations where ambiguity arises--in this case, the first declaration takes precedence. </p> - <p>Please refer to the <a href="SWIGPlus.html#SWIGPlus">"SWIG and C++"</a> chapter for more information about overloading. <a name="n21"></a> </p> - <h3><a name="Ruby_nn21"></a>30.3.10 C++ Operators</h3> - <p> For the most part, overloaded operators are handled automatically by SWIG and do not require any special treatment on your part. So if your class declares an overloaded addition operator, e.g. </p> - <div class="code"> <pre>class Complex {<br> ...<br> Complex operator+(Complex &);<br> ...<br>};<br></pre> - </div> - <p> the resulting Ruby class will also support the addition (+) method correctly. </p> - <p>For cases where SWIG's built-in support is not sufficient, C++ operators can be wrapped using the <tt>%rename</tt> directive (available on SWIG 1.3.10 and later releases). All you need to do is give the operator the name of a valid Ruby identifier. For example: </p> - <div class="code"> <pre>%rename(add_complex) operator+(Complex &, Complex &);<br>...<br>Complex operator+(Complex &, Complex &);<br></pre> - </div> - <p>Now, in Ruby, you can do this:</p> - <div class="code targetlang"> <pre>a = Example::Complex.new(2, 3)<br>b = Example::Complex.new(4, -1)<br>c = Example.add_complex(a, b)<br></pre> - </div> - <p> More details about wrapping C++ operators into Ruby operators is discussed in the <a href="#ruby_operator_overloading">section on operator overloading</a>. </p> - <h3><a name="Ruby_nn22"></a>30.3.11 C++ namespaces</h3> - <p> SWIG is aware of C++ namespaces, but namespace names do not appear in the module nor do namespaces result in a module that is broken up into submodules or packages. For example, if you have a file like this, </p> - <div class="code"> <pre>%module example<br><br>namespace foo {<br> int fact(int n);<br> struct Vector {<br> double x,y,z;<br> };<br>};<br></pre> - </div> - <p>it works in Ruby as follows:</p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>require 'example'</b><br>true<br>irb(main):002:0> <b>Example.fact(3)</b><br>6<br>irb(main):003:0> <b>v = Example::Vector.new</b><br>#<Example::Vector:0x4016f4d4><br>irb(main):004:0> <b>v.x = 3.4</b><br>3.4<br>irb(main):004:0> <b>v.y</b><br>0.0<br></pre> - </div> - <p> If your program has more than one namespace, name conflicts (if any) can be resolved using <tt>%rename</tt> For example: </p> - <div class="code"> <pre>%rename(Bar_spam) Bar::spam;<br><br>namespace Foo {<br> int spam();<br>}<br><br>namespace Bar {<br> int spam();<br>}<br></pre> - </div> - <p> If you have more than one namespace and your want to keep their symbols separate, consider wrapping them as separate SWIG modules. For example, make the module name the same as the namespace @@ -1561,35 +1159,29 @@ program utilizes thousands of small deeply nested namespaces each with identical symbol names, well, then you get what you deserve. </p> - <h3><a name="Ruby_nn23"></a>30.3.12 C++ templates</h3> - <p> C++ templates don't present a huge problem for SWIG. However, in order to create wrappers, you have to tell SWIG to create wrappers for a particular template instantiation. To do this, you use the <tt>%template</tt> directive. For example: </p> - <div class="code"> <pre>%module example<br><br>%{<br>#include "pair.h"<br>%}<br><br>template<class T1, class T2><br>struct pair {<br> typedef T1 first_type;<br> typedef T2 second_type;<br> T1 first;<br> T2 second;<br> pair();<br> pair(const T1&, const T2&);<br> ~pair();<br>};<br><br>%template(Pairii) pair<int,int>;<br></pre> - </div> - <p>In Ruby:</p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>require 'example'</b><br>true<br>irb(main):002:0> <b>p = Example::Pairii.new(3, 4)</b><br>#<Example:Pairii:0x4016f4df><br>irb(main):003:0> <b>p.first</b><br>3<br>irb(main):004:0> <b>p.second</b><br>4<br></pre> - </div> +<h3><a name="Ruby_nn23_1"></a>30.3.12.1 C++ +Standard Template Library (STL)</h3> -<h3><a name="Ruby_nn23_1"></a>30.3.12.1 C++ Standard Template Library (STL)</h3> <p> On a related note, the standard SWIG library contains a number of modules that provide typemaps for standard C++ library classes (such as <tt>std::pair</tt>, <tt>std::string</tt> @@ -1600,152 +1192,163 @@ of standard C++ templates. For example, suppose the C++ library you're wrapping has a function that expects a vector of floats: </p> - <div class="code"> <pre>%module example<br><br>float sum(const std::vector<float>& values);<br></pre> - </div> - <p> Rather than go through the hassle of writing an "in" typemap to convert an array of Ruby numbers into a std::vector<float>, you can just use the <tt>std_vector.i</tt> module from the standard SWIG library: </p> - <div class="code"> <pre>%module example<br><br><b>%include std_vector.i</b><br>float sum(const std::vector<float>& values);<br></pre> - </div> +<p>Ruby's STL wrappings provide additional methods to make them +behave more similarly to Ruby's native classes.</p> -<p>Ruby's STL wrappings provide additional methods to make them behave more similarly to Ruby's native classes.</p> <p>Thus, you can do, for example:</p> + <div class="targetlang"> <pre>v = IntVector.new<span class="targetlang"><br>v << 2</span><span class="targetlang"><br>v << 3<br>v << 4<br>v.each { |x| puts x }<br><span style="font-weight: bold;"><br>=> 2</span><br style="font-weight: bold;"><span style="font-weight: bold;">3</span><br style="font-weight: bold;"><span style="font-weight: bold;">4<br></span>v.delete_if { |x| x == 3 }<br><span style="font-weight: bold;">=> [2,4]</span><span style="font-weight: bold;"></span></span></pre> + </div> + <p>The SWIG Ruby module provides also the ability for all the STL containers to carry around Ruby native objects (Fixnum, Classes, etc) -making them act almost like Ruby's own Array, Hash, etc. To do +making them act almost like Ruby's own Array, Hash, etc. To +do that, you need to define a container that contains a swig::GC_VALUE, like:</p> -<div style="font-family: monospace;" class="code">%module nativevector<br> + +<div style="font-family: monospace;" class="code">%module +nativevector<br> + <br> + %{<br> + std::vector< swig::GC_VALUE > NativeVector;<br> + %}<br> + <br> + %template(NativeVector) std::vector< swig::GC_VALUE >;<br> + </div> + <br> -<p>This vector can then contain any Ruby object, making them almost identical to Ruby's own Array class.</p> + +<p>This vector can then contain any Ruby object, making them +almost identical to Ruby's own Array class.</p> + <div class="targetlang"><span style="font-family: monospace;">require 'nativevector'</span><br style="font-family: monospace;"> + <span style="font-family: monospace;">include NativeVector</span><br style="font-family: monospace;"> + <br style="font-family: monospace;"> + <span style="font-family: monospace;">v = NativeVector.new</span><br style="font-family: monospace;"> + <span style="font-family: monospace;">v << 1</span><br style="font-family: monospace;"> -<span style="font-family: monospace;">v << [1,2]</span><br style="font-family: monospace;"> -<span style="font-family: monospace;">v << 'hello'</span><br style="font-family: monospace;"> + +<span style="font-family: monospace;">v << +[1,2]</span><br style="font-family: monospace;"> + +<span style="font-family: monospace;">v << +'hello'</span><br style="font-family: monospace;"> + <br style="font-family: monospace;"> + <span style="font-family: monospace;">class A; end</span><br style="font-family: monospace;"> + <br style="font-family: monospace;"> -<span style="font-family: monospace;">v << A.new</span><br style="font-family: monospace;"> + +<span style="font-family: monospace;">v << +A.new</span><br style="font-family: monospace;"> + <br style="font-family: monospace;"> + <span style="font-family: monospace;">puts v</span><br style="font-family: monospace;"> -<span style="font-weight: bold; font-family: monospace;">=> [1, [1,2], 'hello', #<A:0x245325>]</span></div> + +<span style="font-weight: bold; font-family: monospace;">=> +[1, [1,2], 'hello', #<A:0x245325>]</span></div> + <br> + <p>Obviously, there is a lot more to template wrapping than shown in these examples. More details can be found in the <a href="SWIGPlus.html#SWIGPlus">SWIG and C++</a> chapter.</p> + <h3><a name="Ruby_nn24"></a>30.3.13 C++ Smart Pointers</h3> - <p> In certain C++ programs, it is common to use classes that have been wrapped by so-called "smart pointers." Generally, this involves the use of a template class that implements <tt>operator->()</tt> like this: </p> - <div class="code"> <pre>template<class T> class SmartPtr {<br> ...<br> T *operator->();<br> ...<br>}<br></pre> - </div> - <p>Then, if you have a class like this,</p> - <div class="code"> <pre>class Foo {<br>public:<br> int x;<br> int bar();<br>};<br></pre> - </div> - <p>A smart pointer would be used in C++ as follows:</p> - <div class="code"> <pre>SmartPtr<Foo> p = CreateFoo(); // Created somehow (not shown)<br>...<br>p->x = 3; // Foo::x<br>int y = p->bar(); // Foo::bar<br></pre> - </div> - <p> To wrap this in Ruby, simply tell SWIG about the <tt>SmartPtr</tt> class and the low-level <tt>Foo</tt> object. Make sure you instantiate <tt>SmartPtr</tt> using <tt>%template</tt> if necessary. For example: </p> - <div class="code"> <pre>%module example<br>...<br>%template(SmartPtrFoo) SmartPtr<Foo>;<br>...<br></pre> - </div> - <p>Now, in Ruby, everything should just "work":</p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>p = Example::CreateFoo()</b> # Create a smart-pointer somehow<br>#<Example::SmartPtrFoo:0x4016f4df><br>irb(main):002:0> <b>p.x = 3</b> # Foo::x<br>3<br>irb(main):003:0> <b>p.bar()</b> # Foo::bar<br></pre> - </div> - <p> If you ever need to access the underlying pointer returned by <tt>operator->()</tt> itself, simply use the <tt>__deref__()</tt> method. For example: </p> - <div class="code targetlang"> <pre>irb(main):004:0> <b>f = p.__deref__()</b> # Returns underlying Foo *<br></pre> - </div> - <h3><a name="Ruby_nn25"></a>30.3.14 Cross-Language Polymorphism</h3> - <p> SWIG's Ruby module supports cross-language polymorphism (a.k.a. the "directors" feature) similar to that for SWIG's Python module. Rather than duplicate the information presented in the <a href="Ruby">Python</a> chapter, this section just notes the differences that you need to be aware of when using this feature with Ruby. </p> - <h4><a name="Ruby_nn26"></a>30.3.14.1 Exception Unrolling</h4> - <p> Whenever a C++ director class routes one of its virtual member function calls to a Ruby instance method, there's always the possibility that an exception will be raised in the Ruby code. By @@ -1755,81 +1358,62 @@ directive to indicate what action should be taken when a Ruby exception is raised. The following code should suffice in most cases: </p> - <div class="code"> <pre>%feature("director:except") {<br> throw Swig::DirectorMethodException($error);<br>}<br></pre> - </div> - <p> When this feature is activated, the call to the Ruby instance method is "wrapped" using the <tt>rb_rescue2()</tt> function from Ruby's C API. If any Ruby exception is raised, it will be caught here and a C++ exception is raised in its place. </p> - <h2><a name="Ruby_nn27"></a>30.4 Naming</h2> - <p>Ruby has several common naming conventions. Constants are generally in upper case, module and class names are in camel case and methods are in lower case with underscores. For example: </p> - <div class="code"> <ul> - <li><strong>MATH::PI</strong> is a constant name</li> - <li><strong>MyClass</strong> is a class name</li> - <li><strong>my_method</strong> is a method name</li> - </ul> - </div> - <p>Prior to version 1.3.28, SWIG did not support these Ruby conventions. The only modifications it made to names was to capitalize the first letter of constants (which includes module and class names).</p> - <p>SWIG 1.3.28 introduces the new -autorename command line parameter. When this parameter is specified, SWIG will automatically change constant, class and method names to conform with the standard Ruby naming conventions. For example: </p> - <div class="code shell"> <pre>$ <b>swig -ruby -autorename example.i</b> </pre> - </div> - <p>To disable renaming use the -noautorename command line option.</p> - <p>Since this change significantly changes the wrapper code generated by SWIG, it is turned off by default in SWIG 1.3.28. However, it is planned to become the default option in future releases.</p> - <h3><a name="Ruby_nn28"></a>30.4.1 Defining Aliases</h3> - <p> It's a fairly common practice in the Ruby built-ins and standard library to provide aliases for method names. For example, <em>Array#size</em> is an alias for <em>Array#length</em>. If you would like @@ -1838,38 +1422,29 @@ add a new method of the aliased name that calls the original function. For example: </p> - <div class="code"> <pre>class MyArray {<br>public:<br> // Construct an empty array<br> MyArray();<br> <br> // Return the size of this array<br> size_t length() const;<br>};<br><br>%extend MyArray {<br> // MyArray#size is an alias for MyArray#length<br> size_t size() const {<br> return $self->length();<br> }<br>}<br> </pre> - </div> - <p> A better solution is to use the <tt>%alias</tt> directive (unique to SWIG's Ruby module). The previous example could then be rewritten as: </p> - <div class="code"> <pre>// MyArray#size is an alias for MyArray#length<br>%alias MyArray::length "size";<br><br>class MyArray {<br>public:<br> // Construct an empty array<br> MyArray();<br> <br> // Return the size of this array<br> size_t length() const;<br>};<br><br></pre> - </div> - <p> Multiple aliases can be associated with a method by providing a comma-separated list of aliases to the <tt>%alias</tt> directive, e.g. </p> - <div class="code"> <pre>%alias MyArray::length "amount,quantity,size";</pre> - </div> - <p> From an end-user's standpoint, there's no functional difference between these two approaches; i.e. they should get the same result from calling either <em>MyArray#size</em> or <em>MyArray#length</em>. @@ -1878,18 +1453,15 @@ associated with added methods like our <em>MyArray::size()</em> example. </p> - <p>Note that the <tt>%alias</tt> directive is implemented using SWIG's "features" mechanism and so the same name matching rules used for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization Features"</a>) for more details).</p> - <h3><a name="Ruby_nn29"></a>30.4.2 Predicate Methods</h3> - <p> Ruby methods that return a boolean value and end in a question mark are known as predicate methods. Examples of predicate methods in @@ -1900,52 +1472,40 @@ with Ruby conventions, methods that return boolean values should be marked as predicate methods.</p> - <p>One cumbersome solution to this problem is to rename the method (using SWIG's <tt>%rename</tt> directive) and provide a custom typemap that converts the function's actual return type to Ruby's <tt>true</tt> or <tt>false</tt>. For example: </p> - <div class="code"> <pre>%rename("is_it_safe?") is_it_safe();<br><br>%typemap(out) int is_it_safe <br> "$result = ($1 != 0) ? Qtrue : Qfalse;";<br><br>int is_it_safe();<br><br></pre> - </div> - <p> A better solution is to use the <tt>%predicate</tt> directive (unique to SWIG's Ruby module) to designate a method as a predicate method. For the previous example, this would look like: </p> - <div class="code"> <pre>%predicate is_it_safe();<br><br>int is_it_safe();<br><br></pre> - </div> - <p>This method would be invoked from Ruby code like this:</p> - <div class="code targetlang"> <pre>irb(main):001:0> <b>Example::is_it_safe?</b><br>true<br><br></pre> - </div> - <p> The <tt>%predicate</tt> directive is implemented using SWIG's "features" mechanism and so the same name matching rules used for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization Features"</a>) for more details). </p> - <h3><a name="Ruby_nn30"></a>30.4.3 Bang Methods</h3> - <p> Ruby methods that modify an object in-place and end in an exclamation mark are known as bang methods. An example of a bang method is <em>Array#sort!</em> which changes the ordering of @@ -1954,513 +1514,446 @@ modifying the original array. For consistency with Ruby conventions, methods that modify objects in place should be marked as bang methods.</p> - <p>Bang methods can be marked using the <tt>%bang</tt> directive which is unique to the Ruby module and was introduced in SWIG 1.3.28. For example:</p> - <div class="code"> <pre>%bang sort!(arr);<br><br>int sort(int arr[]); </pre> - </div> - <p>This method would be invoked from Ruby code like this:</p> - <div class="code"> <pre>irb(main):001:0> <b>Example::sort!(arr)</b></pre> - </div> - <p> The <tt>%bang</tt> directive is implemented using SWIG's "features" mechanism and so the same name matching rules used for other kinds of features apply (see the chapter on <a href="Customization.html#Customization">"Customization Features"</a>) for more details). </p> - <h3><a name="Ruby_nn31"></a>30.4.4 Getters and Setters</h3> - <p> Often times a C++ library will expose properties through getter and setter methods. For example:</p> - <div class="code"> <pre>class Foo {<br> Foo() {}<br><br> int getValue() { return value_; }<br><br> void setValue(int value) { value_ = value; }<br><br>private:<br> int value_;<br>};</pre> - </div> - <p>By default, SWIG will expose these methods to Ruby as <tt>get_value</tt> and <tt>set_value.</tt> However, it more natural for these methods to be exposed in Ruby as <tt>value</tt> and <tt>value=. </tt> That allows the methods to be used like this:</p> - <div class="code"> <pre>irb(main):001:0> <b>foo = Foo.new()</b><br>irb(main):002:0> <b>foo.value = 5</b><br>irb(main):003:0> <b>puts foo.value</b></pre> - </div> - <p> This can be done by using the %rename directive:</p> - <div class="code"> <pre>%rename("value") Foo::getValue();<br>%rename("value=") Foo::setValue(int value);<br></pre> - </div> - <p> </p> - <h2><a name="Ruby_nn32"></a>30.5 Input and output parameters</h2> - <p> A common problem in some C programs is handling parameters passed as simple pointers. For example: </p> - <div class="code"> <pre>void add(int x, int y, int *result) {<br> *result = x + y;<br>}<br>or<br>int sub(int *x, int *y) {<br> return *x-*y;<br>}<br></pre> - </div> - <p> The easiest way to handle these situations is to use the <tt>typemaps.i</tt> file. For example: </p> - <div class="code"> <pre>%module Example<br>%include "typemaps.i"<br><br>void add(int, int, int *OUTPUT);<br>int sub(int *INPUT, int *INPUT);<br></pre> - </div> - <p>In Ruby, this allows you to pass simple values. For example:</p> - <div class="code targetlang"> <pre>a = Example.add(3,4)<br>puts a<br>7<br>b = Example.sub(7,4)<br>puts b<br>3<br></pre> - </div> - <p> Notice how the <tt>INPUT</tt> parameters allow integer values to be passed instead of pointers and how the <tt>OUTPUT</tt> parameter creates a return result. </p> - <p>If you don't want to use the names <tt>INPUT</tt> or <tt>OUTPUT</tt>, use the <tt>%apply</tt> directive. For example: </p> - <div class="code"> <pre>%module Example<br>%include "typemaps.i"<br><br>%apply int *OUTPUT { int *result };<br>%apply int *INPUT { int *x, int *y};<br><br>void add(int x, int y, int *result);<br>int sub(int *x, int *y);<br></pre> - </div> - <p> If a function mutates one of its parameters like this, </p> - <div class="code"> <pre>void negate(int *x) {<br> *x = -(*x);<br>}<br></pre> - </div> - <p>you can use <tt>INOUT</tt> like this:</p> - <div class="code"> <pre>%include "typemaps.i"<br>...<br>void negate(int *INOUT);<br></pre> - </div> - <p>In Ruby, a mutated parameter shows up as a return value. For example:</p> - <div class="code targetlang"> <pre>a = Example.negate(3)<br>print a<br>-3<br><br></pre> - </div> - <p> The most common use of these special typemap rules is to handle functions that return more than one value. For example, sometimes a function returns a result as well as a special error code: </p> - <div class="code"> <pre>/* send message, return number of bytes sent, success code, and error_code */<br>int send_message(char *text, int *success, int *error_code);<br></pre> - </div> - <p> To wrap such a function, simply use the <tt>OUTPUT</tt> rule above. For example: </p> - <div class="code"> <pre>%module example<br>%include "typemaps.i"<br>...<br>int send_message(char *, int *OUTPUT, int *OUTPUT);<br></pre> - </div> - <p> When used in Ruby, the function will return an array of multiple values. </p> - <div class="code targetlang"> <pre>bytes, success, error_code = send_message("Hello World")<br>if not success<br> print "error #{error_code} : in send_message"<br>else<br> print "Sent", bytes<br>end<br></pre> - </div> - <p> Another way to access multiple return values is to use the <tt>%apply</tt> rule. In the following example, the parameters rows and columns are related to SWIG as <tt>OUTPUT</tt> values through the use of <tt>%apply</tt> </p> - <div class="code"> <pre>%module Example<br>%include "typemaps.i"<br>%apply int *OUTPUT { int *rows, int *columns };<br>...<br>void get_dimensions(Matrix *m, int *rows, int*columns);<br></pre> - </div> - <p>In Ruby:</p> - <div class="code targetlang"> <pre>r, c = Example.get_dimensions(m)<br></pre> - </div> - <h2><a name="Ruby_nn33"></a>30.6 Exception handling </h2> - <h3><a name="Ruby_nn34"></a>30.6.1 Using the %exception directive </h3> - <p>The SWIG <tt>%exception</tt> directive can be used to define a user-definable exception handler that can convert C/C++ errors into Ruby exceptions. The chapter on <a href="Customization.html#Customization">Customization Features</a> contains more details, but suppose you have a C++ class like the following : </p> - <div class="code"> <pre>class DoubleArray {<br> private:<br> int n;<br> double *ptr;<br> public:<br> // Create a new array of fixed size<br> DoubleArray(int size) {<br> ptr = new double[size];<br> n = size;<br> }<br><br> // Destroy an array<br> ~DoubleArray() {<br> delete ptr;<br> } <br><br> // Return the length of the array<br> int length() {<br> return n;<br> }<br><br> // Get an array item and perform bounds checking.<br> double getitem(int i) {<br> if ((i >= 0) && (i < n))<br> return ptr[i];<br> else<br> throw RangeError();<br> }<br><br> // Set an array item and perform bounds checking.<br> void setitem(int i, double val) {<br> if ((i >= 0) && (i < n))<br> ptr[i] = val;<br> else {<br> throw RangeError();<br> }<br> }<br> };<br></pre> - </div> - <p> Since several methods in this class can throw an exception for an out-of-bounds access, you might want to catch this in the Ruby extension by writing the following in an interface file: </p> - <div class="code"> <pre>%exception {<br> try {<br> $action<br> }<br> catch (const RangeError&) {<br> static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);<br> rb_raise(cpperror, "Range error.");<br> }<br>}<br><br>class DoubleArray {<br> ...<br>};<br></pre> - </div> - <p> The exception handling code is inserted directly into generated wrapper functions. When an exception handler is defined, errors can be caught and used to gracefully raise a Ruby exception instead of forcing the entire program to terminate with an uncaught error. </p> - <p>As shown, the exception handling code will be added to every wrapper function. Because this is somewhat inefficient, you might consider refining the exception handler to only apply to specific methods like this: </p> - <div class="code"> <pre>%exception getitem {<br> try {<br> $action<br> }<br> catch (const RangeError&) {<br> static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);<br> rb_raise(cpperror, "Range error in getitem.");<br> }<br>}<br><br>%exception setitem {<br> try {<br> $action<br> }<br> catch (const RangeError&) {<br> static VALUE cpperror = rb_define_class("CPPError", rb_eStandardError);<br> rb_raise(cpperror, "Range error in setitem.");<br> }<br>}<br></pre> - </div> - <p> In this case, the exception handler is only attached to methods and functions named <tt>getitem</tt> and <tt>setitem</tt>. </p> - <p>Since SWIG's exception handling is user-definable, you are not limited to C++ exception handling. See the chapter on <a href="Customization.html#Customization">Customization -Features</a> for more examples. </p> +Features</a> for more examples.</p> +<h3><a name="Ruby_nn34_2"></a>30.6.2 Handling +Ruby Blocks </h3> -<h3><a name="Ruby_nn35"></a>30.6.2 Raising -exceptions </h3> +<p>One of the highlights of Ruby and most of its standard library +is +the use of blocks, which allow the easy creation of continuations and +other niceties. &nbs... [truncated message content] |