Re: [Swig-user] std::wstring as an output parameter by reference

[Sergio G. V. @ DAMA-U. <sg...@ac...>]

Any suggestion about that?

Thanks,
Sergio

On May 5, 2011, at 8:26 AM, Sergio Gómez Villamor @ DAMA-UPC wrote:

> Hi all,
> 
> I want to wrap this function (to Java and C#):
> 	void MyClass::GetName(std::wstring &name);
> where name is an output parameter to get the name.
> 
> Of course, I have included std_wstring.i as well as I have added the corresponding apply for non-const wstrings.
> But wrapped code wraps the argument as an input parameter:
> 
> SWIGEXPORT void JNICALL Java_MyClass_1GetAlias(JNIEnv *jenv, jclass jcls, jlong     jarg1, jobject jarg1_, jstring jarg2) {
>   ...
>   const jchar *arg2_pstr = jenv->GetStringChars(jarg2, 0);
>   if (!arg2_pstr) return ;
>   jsize arg2_len = jenv->GetStringLength(jarg2);
>   std::wstring arg2_str;
>   if (arg2_len) {
>      arg2_str.reserve(arg2_len);
>      for (jsize i = 0; i < arg2_len; ++i) {
>         arg2_str.push_back((wchar_t)arg2_pstr[i]);
>      }
>   }
>   arg2 = &arg2_str;
>   jenv->ReleaseStringChars(jarg2, arg2_pstr);
> 
>   (arg1)->GetName(*arg2);
>   return ;
> }
> 
> 
> After that, I have tried adding this to the swig interface file:
> 	%apply std::wstring &OUTPUT { std::wstring &name};
> But it didn't worked getting this warning:
> 	dexjava.i:92: Warning 453: Can't apply (std::wstring &OUTPUT). No typemaps are defined.
> 
> 
> I've read the documentation of std_wstring and I guess this is the problem:
> "
>  7  * To use non-const std::wstring references use the following %apply.  Note 
>  8  * that they are passed by value.
> "
> 
> 
> But, do you have a solution for this scenario?
> 
> Thanks in advance,
> Sergio