Enhance %extend to extend a class with template methods

CHANGES.current

@@ -7,6 +7,19 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 3.0.12 (in progress)
 ============================
 
+2017-01-22: wsfulton
+            Issue #876 Enhance %extend to extend a class with template methods, eg:
+
+              struct Foo {
+                %extend {
+                  template<typename T>
+                  void do_stuff(int a, T b) {
+                    ...
+                  }
+                }
+              };
+              %template(do_stuff_inst) Foo::do_stuff<double>;
+
 2017-01-22: kwwette
             [Octave] add support for version 4.2
             - The Octave API now uses some C++11 features. It is recommended to use

Doc/Manual/SWIGPlus.html

@@ -3635,6 +3635,43 @@ This will generate two overloaded wrapper methods, the first will take a single
 and the second will take two integer arguments.
 </p>
 
+<p>
+It is even possible to extend a class via <tt>%extend</tt> with template methods, for example:
+</p>
+
+<div class="code">
+<pre>
+%include &lt;std_string.i&gt;
+
+%inline %{
+class ExtendMe {
+public:
+  template &lt;typename T&gt;
+  T do_stuff_impl(int a, T b, double d) {
+    return b;
+  }
+};
+%}
+
+%extend ExtendMe {
+  template&lt;typename T&gt;
+  T do_overloaded_stuff(T b) {
+    return $self-&gt;do_stuff_impl(0, b, 4.0);
+  }
+}
+%template(do_overloaded_stuff) ExtendMe::do_overloaded_stuff&lt;std::string&gt;;
+%template(do_overloaded_stuff) ExtendMe::do_overloaded_stuff&lt;double&gt;;
+</pre>
+</div>
+
+<p>
+The wrapped <tt>ExtendMe</tt> class will then have two (overloaded) methods called <tt>do_overloaded_stuff</tt>.
+</p>
+
+<p>
+<b>Compatibility Note</b>:  Extending a class with template methods was added in version 3.0.12
+</p>
+
 <p>
 Needless to say, SWIG's template support provides plenty of opportunities to
 break the universe.  That said, an important final point is that <b>SWIG does

Examples/test-suite/common.mk

@@ -227,6 +227,7 @@ CPP_TEST_CASES += \
 	extend_placement \
 	extend_special_variables \
 	extend_template \
+	extend_template_method \
 	extend_template_ns \
 	extend_typedef_class \
 	extern_c \

Examples/test-suite/extend_template_method.i

@@ -0,0 +1,62 @@
+%module extend_template_method
+
+%include <std_string.i>
+
+%inline %{
+class ExtendMe {
+public:
+  template <typename T>
+  T do_stuff_impl(int a, T b, double d) {
+    return b;
+  }
+};
+%}
+
+%extend ExtendMe {
+  template<typename T>
+  T do_stuff(int a, T b) {
+    return $self->do_stuff_impl(a, b, 4.0);
+  }
+  template<typename T>
+  T do_overloaded_stuff(T b) {
+    return $self->do_stuff_impl(0, b, 4.0);
+  }
+}
+%template(do_stuff_double) ExtendMe::do_stuff<double>;
+%template(do_stuff_string) ExtendMe::do_stuff<std::string>;
+
+%template(do_overloaded_stuff) ExtendMe::do_overloaded_stuff<std::string>;
+%template(do_overloaded_stuff) ExtendMe::do_overloaded_stuff<double>;
+
+
+%inline %{
+template<typename X>
+class TemplateExtendMe {
+public:
+  template <typename T>
+  T template_stuff_impl(X a, T b, double d) {
+    return b;
+  }
+};
+%}
+
+%extend TemplateExtendMe {
+  template<typename T>
+  T do_template_stuff(int a, T b) {
+    return $self->template_stuff_impl(a, b, 4.0);
+  }
+  template<typename T>
+  T do_template_overloaded_stuff(T b) {
+    return $self->template_stuff_impl(0, b, 4.0);
+  }
+
+%template(do_template_stuff_double) do_template_stuff<double>;
+%template(do_template_stuff_string) do_template_stuff<std::string>;
+
+%template(do_template_overloaded_stuff) do_template_overloaded_stuff<std::string>;
+%template(do_template_overloaded_stuff) do_template_overloaded_stuff<double>;
+
+}
+
+%template(TemplateExtend) TemplateExtendMe<int>;
+

Examples/test-suite/java/extend_template_method_runme.java

@@ -0,0 +1,57 @@
+
+import extend_template_method.*;
+
+public class extend_template_method_runme {
+
+  static {
+    try {
+	System.loadLibrary("extend_template_method");
+    } catch (UnsatisfiedLinkError e) {
+      System.err.println("Native code library failed to load. See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help.\n" + e);
+      System.exit(1);
+    }
+  }
+
+  public static void main(String argv[]) {
+    {
+      ExtendMe em = new ExtendMe();
+
+      {
+        double ret_double = em.do_stuff_double(1, 1.1);
+        if (ret_double != 1.1)
+          throw new RuntimeException("double failed " + ret_double);
+        String ret_string = em.do_stuff_string(1, "hello there");
+        if (!ret_string.equals("hello there"))
+          throw new RuntimeException("string failed " + ret_string);
+      }
+      {
+        double ret_double = em.do_overloaded_stuff(1.1);
+        if (ret_double != 1.1)
+          throw new RuntimeException("double failed " + ret_double);
+        String ret_string = em.do_overloaded_stuff("hello there");
+        if (!ret_string.equals("hello there"))
+          throw new RuntimeException("string failed " + ret_string);
+      }
+    }
+    {
+      TemplateExtend em = new TemplateExtend();
+
+      {
+        double ret_double = em.do_template_stuff_double(1, 1.1);
+        if (ret_double != 1.1)
+          throw new RuntimeException("double failed " + ret_double);
+        String ret_string = em.do_template_stuff_string(1, "hello there");
+        if (!ret_string.equals("hello there"))
+          throw new RuntimeException("string failed " + ret_string);
+      }
+      {
+        double ret_double = em.do_template_overloaded_stuff(1.1);
+        if (ret_double != 1.1)
+          throw new RuntimeException("double failed " + ret_double);
+        String ret_string = em.do_template_overloaded_stuff("hello there");
+        if (!ret_string.equals("hello there"))
+          throw new RuntimeException("string failed " + ret_string);
+      }
+    }
+  }
+}

Examples/test-suite/python/extend_template_method_runme.py

@@ -0,0 +1,36 @@
+from extend_template_method import *
+
+
+em = ExtendMe()
+
+ret_double = em.do_stuff_double(1, 1.1)
+if ret_double != 1.1:
+    raise RuntimeError("double failed " + ret_double)
+ret_string = em.do_stuff_string(1, "hello there")
+if ret_string != "hello there":
+    raise RuntimeError("string failed " + ret_string)
+
+ret_double = em.do_overloaded_stuff(1.1)
+if ret_double != 1.1:
+    raise RuntimeError("double failed " + ret_double)
+ret_string = em.do_overloaded_stuff("hello there")
+if ret_string != "hello there":
+    raise RuntimeError("string failed " + ret_string)
+
+
+em = TemplateExtend()
+
+ret_double = em.do_template_stuff_double(1, 1.1)
+if ret_double != 1.1:
+    raise RuntimeError("double failed " + ret_double)
+ret_string = em.do_template_stuff_string(1, "hello there")
+if ret_string != "hello there":
+    raise RuntimeError("string failed " + ret_string)
+
+
+ret_double = em.do_template_overloaded_stuff(1.1)
+if ret_double != 1.1:
+    raise RuntimeError("double failed " + ret_double)
+ret_string = em.do_template_overloaded_stuff("hello there")
+if ret_string != "hello there":
+    raise RuntimeError("string failed " + ret_string)

Source/Modules/lang.cxx

@@ -1267,7 +1267,7 @@ int Language::memberfunctionHandler(Node *n) {
   if (GetFlag(n, "explicitcall"))
     DirectorExtraCall = CWRAP_DIRECTOR_ONE_CALL;
 
-  Swig_MethodToFunction(n, NSpace, ClassType, Getattr(n, "template") ? SmartPointer : Extend | SmartPointer | DirectorExtraCall, director_type,
+  Swig_MethodToFunction(n, NSpace, ClassType, Getattr(n, "template") ? Extend | SmartPointer : Extend | SmartPointer | DirectorExtraCall, director_type,
 			is_member_director(CurrentClass, n));
   Setattr(n, "sym:name", fname);