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Add examples extending generated proxy class using partial classes and cscode typemap

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William S Fulton 2007-08-15 20:37:24 +00:00
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@ -29,6 +29,8 @@
<li><a href="#csharp_memory_management_member_variables">Memory management when returning references to member variables</a>
<li><a href="#csharp_memory_management_objects">Memory management for objects passed to the C++ layer</a>
<li><a href="#csharp_date_marshalling">Date marshalling using the csin typemap and associated attributes</a>
<li><a href="#csharp_partial_classes">Turning wrapped classes into partial classes</a>
<li><a href="#csharp_extending_proxy_class">Extending proxy classes with additional C# code</a>
</ul>
</ul>
</div>
@ -1720,6 +1722,143 @@ A few things to note:
<li> The 'cshin' attribute is required for the <tt>SwigConstructAction</tt> constructor helper function so that the 2nd parameter is declared as <tt>ref dateOut</tt> instead of just <tt>dateOut</tt>.
</ul>
<H3><a name="csharp_partial_classes"></a>17.5.4 Turning wrapped classes into partial classes</H3>
<p>
C# supports the notion of partial classes whereby a class definition can be split into more than one file.
It is possible to turn the wrapped C++ class into a partial C# class using the <tt>csclassmodifiers</tt> typemap.
Consider a C++ class called <tt>ExtendMe</tt>:
</p>
<div class="code">
<pre>
class ExtendMe {
public:
int Part1() { return 1; }
};
</pre>
</div>
<p>
The default C# proxy class generated is:
</p>
<div class="code">
<pre>
public class ExtendMe : IDisposable {
...
public int Part1() {
...
}
}
</pre>
</div>
<p>
The default csclassmodifiers typemap shipped with SWIG is
</p>
<div class="code">
<pre>
%typemap(csclassmodifiers) SWIGTYPE "public class"
</pre>
</div>
<p>
If instead we use the following typemap to override this for just the <tt>ExtendMe</tt> class:
</p>
<div class="code">
<pre>
%typemap(csclassmodifiers) ExtendMe "public partial class"
</pre>
</div>
<p>
The C# proxy class becomes a partial class:
</p>
<div class="code">
<pre>
public partial class ExtendMe : IDisposable {
...
public int Part1() {
...
}
}
</pre>
</div>
<p>
You can then of course declare another part of the partial class elsewhere, for example:
</p>
<div class="code">
<pre>
public partial class ExtendMe : IDisposable {
public int Part2() {
return 2;
}
}
</pre>
</div>
<p>
and compile the following code:
</p>
<div class="code">
<pre>
ExtendMe em = new ExtendMe();
Console.WriteLine("part1: {0}", em.Part1());
Console.WriteLine("part2: {0}", em.Part2());
</pre>
</div>
<p>
demonstrating that the class contains methods calling both unmanaged code - <tt>Part1()</tt> and managed code - <tt>Part2()</tt>.
The following example is an alternative approach to adding managed code to the generated proxy class.
</p>
<H3><a name="csharp_extending_proxy_class"></a>17.5.5 Extending proxy classes with additional C# code</H3>
<p>
The previous example showed how to use partial classes to add functionality to a generated C# proxy class.
It is also possible to extend a wrapped struct/class with C/C++ code by using the <a href="SWIGPlus.html#SWIGPlus_class_extension">%extend directive</a>.
A third approach is to add some C# methods into the generated proxy class with the <tt>cscode</tt> typemap.
If we declare the following typemap before SWIG parses the <tt>ExtendMe</tt> class used in the previous example
</p>
<div class="code">
<pre>
%typemap(cscode) ExtendMe %{
public int Part3() {
return 3;
}
%}
</pre>
</div>
<p>
The generated C# proxy class will instead be:
</p>
<div class="code">
<pre>
public class ExtendMe : IDisposable {
...
public int Part3() {
return 3;
}
public int Part1() {
...
}
}
</pre>
</div>
</body>
</html>