New example for Ruby that shows how to implement a mark function. Also makes use of the tracking objects funcitonality.

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@7519 626c5289-ae23-0410-ae9c-e8d60b6d4f22

SWIG/Examples/ruby/mark_function/example.i

@@ -0,0 +1,37 @@
+%module example
+
+%{
+#include "example.h"
+%}
+
+/* Tell SWIG that create_animal creates a new object */
+%newobject Zoo::create_animal;
+
+/* Keep track of mappings between C/C++ structs/classes
+   and Ruby objects so we can implement a mark function. */
+%trackobjects;
+
+
+/* Specify the mark function */
+%markfunc Zoo "mark_Zoo";
+
+%include "example.h"
+
+%header %{
+	static void mark_Zoo(void* ptr) {
+		Zoo* zoo = (Zoo*) ptr;
+
+		/* Loop over each object and tell the garbage collector
+		   that we are holding a reference to them. */
+		int count = zoo->get_num_animals();
+
+		for(int i = 0; i < count; ++i) {
+			Animal* animal = zoo->get_animal(i);
+			VALUE object = SWIG_RubyInstanceFor(animal);
+
+			if (object != Qnil) {
+				rb_gc_mark(object);
+			}
+		}
+	}
+%}