Python typemaps for OptionalValue

python_optional.i

%define DEFINE_OPTIONAL_SIMPLE(OptT, T)

// Use reference, not pointer, typemaps for member variables of this type.
%naturalvar OptionalValue< T >;

// Even though this type is not mentioned anywhere, we must still do this to
// tell SWIG to actually export this type.
%template(OptT) OptionalValue< T >;

// This typemap is used for function arguments and for setting member fields of
// OptionalValue<> type.
//
// Also note the hack with shadowing $1 below: it is a bit ridiculous, but it
// seems like we don't have any way to reuse the typemap defined for T without
// defining this nested variable with the same name as the original one, but
// with the right type. I.e. this $1 intentionally hides the real $1, of type
// "OptionalValue<T>*", so that $typemap() code compiles correctly.
%typemap(in) OptionalValue< T >, const OptionalValue< T >& (OptionalValue< T > tmp_ov) %{
  $1 = &tmp_ov;
  if ($input != Py_None)
  {
    T $1;
    $typemap(in, T)
    tmp_ov.Set($1);
  }
  %}

// For dynamic languages, such as Python, there should be a typecheck typemap
// for each in typemap to allow overloaded functions taking this type to work.
%typemap(typecheck, precedence=SWIG_TYPECHECK_POINTER) OptionalValue< T >, const OptionalValue< T >& (OptionalValue< T > tmp_ov) %{
  if ($input == Py_None)
    $1 = true;
  else {
    $typemap(typecheck, T)
  }
  %}

// This typemap is for functions returning objects of this type.
//
// It again needs to use an ugly trick with shadowing, this time of "result",
// to make the code from $typemap() expansion work correctly.
%typemap(out) OptionalValue< T > %{
  if ( $1.IsValid() )
  {
    OptionalValue< T >& tmp_ov = $1;
    {
      T result = tmp_ov.Get();
      $typemap(out, T)
    }
  }
  else
  {
    $result = Py_None;
    Py_INCREF(Py_None);
  }
  %}

// And this one is for members of this type.
//
// It's basically the same as above, but the type of "$1" is different here.
%typemap(out) OptionalValue< T >& %{
  if ( $1->IsValid() )
  {
    OptionalValue< T >* tmp_ptr = $1;
    {
      T result = tmp_ptr->Get();
      $typemap(out, T)
    }
  }
  else
  {
    $result = Py_None;
    Py_INCREF(Py_None);
  }
  %}


%enddef