Re: [Swig-user] JAVA_ARRAYSOFCLASSES again

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

Jean-Yves Lawson wrote:
> Hi,
> 
> I'm having troubles using the JAVA_ARRAYSOFCLASSES macro with an array 
> of classes declared in c++ like "MyClass** list;". I've read other posts 
> talking about it and succeeded in having simple examples working. 
> However the following configuration does fail:
> 
> ->My MyClassTest.i file contains
> -------MyClassTest.i------------
> %module MyClassTest
> %include "typemaps.i"
> %include "arrays_java.i"
> %include "various.i"
> JAVA_ARRAYSOFCLASSES(MyClass)
> %apply MyClass[] { MyClass** list}
> %include "MyClassDef.h"
> ------------------------------
> 
> 
> ->MyClassDef.h contains
> ------MyClassDef.h -----------
> MyClass{
> public:
> int i;
> int j;
> int foobar();
> bool barfoo();
> };
> 
> class MyClasses{
> public:
>  void bar(int i);
>  void foo();
>  MyClass** list;
> };
> --------------------------------
> 
> 
> ->The generated MyClassTest_wrap.cxx is wrong(but compiles) and contains 
> the following code for accessing the MyClass Array:
> -----MyClassTest_wrap.cxx---------------------
> SWIGEXPORT jlongArray JNICALL 
> Java_myPackage_MyClassTestJNI_MyClasses_1list_1get(JNIEnv *jenv, jclass 
> jcls, jlong jarg1, jobject jarg1_) {
>   jlongArray jresult = 0 ;
>   MyClasses *arg1 = (MyClasses*) 0 ;
>   MyClasses **result = 0 ;
>  
>   (void)jenv;
>   (void)jcls;
>   (void)jarg1_;
>   arg1 = *(MyClasses **)&jarg1;
>   result = (MyClass **) ((arg1)->list);
>   *(MyClass ***)&jresult = result;
>   return jresult;
> }
> ---------------------------------------------------
> 
A 'MyClass** list' out typemap is needed for this wrapper. If you look 
inside the JAVA_ARRAYSOFCLASSES macro you'll see:

%typemap(out) ARRAYSOFCLASSES[ANY]

but no:

%typemap(out) ARRAYSOFCLASSES[]

so when you apply the [] typemaps, you are applying nothing and thus get 
the SWIG default. There are no [] out typemaps because it is impossible 
to know how big the array is that you are marshalling. I suggest you 
take the ARRAYSOFCLASSES[ANY] typemap and modify replacing $1_dim0 with 
the size of the returned array.

> 
> ->The generated Java wrapper is also wrong(and do not compile) as 
> MyClasses.java contains the following accessor code:
> ----------------MyClasses.java-----------------
>   public SWIGTYPE_p_p_MyClass[] getList() {
>     return 
> SWIGTYPE_p_p_MyClass.cArrayWrap(MyClassTestJNI.MyClasses_list_get(swigCPtr, 
> this), false);
>   }
> ----------------------------------------------
> 

This is because you are applying typemaps intended for pointer (array) 
access to a pointer to a pointer. You can fix the java errors by putting 
this after the %apply:

%typemap(jstype) MyClass** list "$*javaclassname[]"
%typemap(javain) MyClass** list "$*javaclassname.cArrayUnwrap($javainput)"
%typemap(javaout) MyClass** list {
     return $*javaclassname.cArrayWrap($jnicall, $owner);
   }

This overrides the applied typemaps which come from the 
JAVA_ARRAYSOFCLASSES macro.

William