Re: [Swig-user] How to add custom code into selected methods of proxy classes?

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

Andras Varga wrote:
> I'm wrapping C++ code into Java, and I'm trying to give pointer
> ownership to wrapped code (like Petr Novotny recently). This is needed with
> insertion methods of wrapped container objects:
> 
>    Foo foo = new Foo();  // wrapped object
>    FooContainer container = new FooContainer(); // wrapped object
>    container.insert(foo);  // here, I want foo's swigMemOwn to be changed to
> false
> 
> I am willing to manually annotate FooContainer.insert() and other such
> methods in
> the SWIG interface file, but so far I found no solution.
> 
> I recognize there isn't a direct way to do it, i.e. there isn't anything like
>    %disown_argument("1")  FooContainer.insert(Foo);
> 
> Currently I would be happy with any means that would let me
> inject some custom code into the generated Java insert() method to take care
> of that. (I would insert a foo.disown() call or something like that).
> 
> So my question is:
> 
> 	*** Is there a way to insert custom code into selected Java wrapper
> methods? ***
> 
> Typemaps are no good here, because they would apply to all methods taking
> Foo, which is not what I need.
> 
Nope. Typemaps will match by the name of the parameter name in addition
to the type. So if you have:

%typemap(javain) Foo *obj "..."
void insert(Foo* obj);
void remove(Foo* object);

the typemap will only apply to types Foo *obj, ie the parameter in the
insert method. Likewise you can match on the return type, using the
method name to provide exact matching:

%typemap(javaout) void FooContainer::insert { ... }

struct FooContainer {
  void insert(Foo* obj);
  void remove(Foo* object);
};

The first approach is probably more appropriate as the disown needs to
be done on the Foo* argument. See the "Memory management for objects
passed to the C++ layer" section in the documentation (Java.html) which
covers this.

William