Re: about DISOWN (Re: [Chicken-users] non-finalized object in SWIG

[Daishi Kato]

Thanks for all those explanations.
I now better understand some of the typemaps.
My resolution for now is putting %apply by a script.

Well, so, here is another question:
I'm wrapping the following class method, and it fails.

class wxControl : public wxWindow {
wxString& GetLabel();
};

8<------8<------8<------8<------8<------

wxchicken_core_wrap.cxx: In function 'void _wrap_wx_control_getslabel___(int, in
t, int, int)':
wxchicken_core_wrap.cxx:27542: error: invalid initialization of non-const refere
nce of type 'wxString&' from a temporary of type 'wxString'
wxchicken_core_wrap.cxx:27551: error: invalid conversion from 'const wxChar*' to
 'char*'
wxchicken_core_wrap.cxx:27551: error:   initializing argument 3 of 'int C_string
(int**, int, char*)'

8<------8<------8<------8<------8<------

I guess the problem is either in my typemaps,
or swig does not support reference returning?

The typemap is:

%typemap(in) wxString& {
  if ($input == C_SCHEME_FALSE) {
    $1 = NULL;
  } else {
    if (!C_swig_is_string ($input)) {
      swig_barf (SWIG_BARF1_BAD_ARGUMENT_TYPE, "Argument #$argnum is not of 
type 'char *'");
    }
    $1 = new wxString(C_c_string($input), C_header_size($input));
  }
}

%typemap(freearg) wxString& {
  if ($1 != NULL) {
    delete $1;
  }
}

%typemap(out) wxString& {
  if ($1 == NULL) {
    $result = C_SCHEME_FALSE;
  } else { 
    int string_len = $1->Len();
    C_word *string_space = C_alloc (C_SIZEOF_STRING (string_len));
    $result = C_string (&string_space, string_len, $1->c_str());
  }
}

%typemap(typecheck, precedence=SWIG_TYPECHECK_STRING) wxString& {
  $1 = C_swig_is_string ($input);
}

%apply wxString& { wxString* }


Daishi

At Fri, 30 Jun 2006 01:01:47 -0500,
John Lenz wrote:
> For the details on how typemaps are matched, see
> http://www.swig.org/Doc1.3/Typemaps.html
> mainly the section "Pattern matching rules"
> 
> No.  Typemaps are just that... they are defined and stored and whatever
> based on types.  As such, the DISOWN typemap is slightly different than
> most typemaps in that you want it to "encode" a property of the
> parameter instead of the type itself.  There are several possible
> solutions...
> 
> 1) Since typemaps encode properties of types and not parameters, change
> the type of the parameter to reflect this.  For example:
> 
> typedef Bar BarDisown;
> %apply SWIGTYPE *DISOWN { BarDisown * };
> 
> and then everywhere in the .i file you use BarDisown instead of Bar.
> 
> 2) SWIG provides a very basic way to match on the parameter, but only
> based on name.  So instead of applying all those things, you can just
> write code like
> 
> class Foo {
>   void Foo(Bar DISOWN);
> };
> 
> where the name of the parameter is DISOWN.  SWIG will use the DISOWN
> typemap for this, no need to add any apply or clear or anything.  If you
> don't like the name, you can do something like
> 
> %apply SWIGTYPE *DISOWN { SWIGTYPE *hey };
> 
> and just use hey everywhere.
> 
> 3) Could encode DISOWN as a %feature instead of as a typemap.  Features
> encode properties of parameters (and classes) instead of types, and so
> you have to specify the feature for every function or class (just like
> you want).  So you could do something like
> 
> %delobject Foo::Foo();
> %delobject *::add_container();
> 
> The %feature (which is what %delobject is) is very powerful at applying
> marks to specific functions and such.
> 
> This was recently added in SWIG version 1.3.28, but has not yet been
> implemented for Chicken (it works for python).  See the section:
> http://www.swig.org/Doc1.3/Customization.html#ownership
> and that whole chapter on how %feature works.  I might look into
> supporting this for chicken, If you would like to use it...
> 
> John