Re: [Swig-user] Problems with Java typemaps to replace an input object parameter with a different type

[William S F. <ws...@fu...>]

Juan Hernando wrote:
> Dear all,
> 
> I'm trying to wrap different C++ namespaces into different Java packages 
> with SWIG 1.3.36 and so far I've been able to work out all the details 
> except one.
> 
> Suppose I have two namespaces A and B that map to Java packages A and B. 
> In both namespaces there is an homonym class Foo which we don't want to 
> rename (actually renaming would solve much of the problems but that's 
> inconvenient from the user perspective).
> In A there is a class like this:
> class Problematic
> {
>      void f(Foo &x);
>      void f(B::Foo &x);
> };
> As the documentation says this type of code causes name clashes in the 
> target language because namespaces are flattened. I could rename one of 
> the overloads but then the C++ code and Java code wouldn't be the same 
> and I want to avoid that.
> 
> So, the solution seems to be providing a typemap for B::Foo &, but I'm 
> not able to get it right.
> 
> First I define a typemap for jstype
> %typemap(jstype) B::Foo & "B.Foo"
> so the Java code looks like this:
> ...
>      public void f(B.Foo x) {
>      ModuleAJNI.f__SWIG_1(swigCPtr, this, B.getCPtr(x), x);
>      }
> ...
> The Java interface is exactly what I want but it doesn't work for 2 
> reasons. First getCPtr is called on the wrong class, so I have to 
> provide a typemap for javain. And then, premature garbage collection 
> parameter doesn't match the type in ModuleAJNI.f__SWIG_1 because I 
> haven't changed jstype. I've tried many possible combinations but 
> without success. The key points are that there is no way to override the 
> type of the permature garbage collection parameter (and I don't want to 
> get rid of it) and that the JNI type is unique so I can't do tricks with 
> the argument list without affecting other points of the C++ code. The 
> closer I got was working fine but since I changed the jni type it 
> affected wrapping of Foo & as a return type.
> 
> Passing the object directly instead of the pointer seems to be a 
> possible solution but that involves direct access to fields in the C++ 
> side, which is cumbersome and not less efficient that getCPtr.
> I'd appreciate very much any idea about how to solve this problem neatly?
> 
I think might be missing something, but the type of the premature 
garbage collection prevention parameter is always long and the following:

%rename(BFoo) B::Foo;
%typemap(jstype) B::Foo & "B.Foo"
%typemap(javain) B::Foo & "B.Foo.getCPtr($javainput)"


generates:

   public void f(B.Foo x) {
     exampleJNI.Problematic_f__SWIG_1(swigCPtr, this, B.Foo.getCPtr(x), x);
   }

which is what I think you want.

William

PS don't forget you can used named typemaps by changing the typemap 
types from B::Foo & to B::Foo &x to target just the x variable.