"Bowman, Michael W. \(MBOWMAN\)" <[EMAIL PROTECTED]> writes:
> I have a situation like the following:
>
> void
> setParms(GtkOpenmapProj* proj, ...) {
> ...
> class->normalize_latitude(proj, ...);
> }
>
> GtkOpenmapProj is a base class that has multiple sub-types. Each of the
> subtypes may
> override the normalize_latitude method of the GtkOpenmapProj class. However,
> I don't
> know which of the subtypes is passed into my function, just that its some
> sub-type of
> GtkOpenmapProj. How do I find which type identifier to feed to
> gtk_type_class() so
> that I can obtain the class struct for the proper sub-type (and use the
> proper
> normalize_latitude function)? How does GTK+ handle polymorphism?
Just look at any example in GTK itself. You should not need the
subtype's class, just GtkOpenmapProjClass, which contains the
normalize_latitude function.
The whole point of virtual functions is you don't have to know the
type of the object, isn't it?
Usually people write a wrapper function:
void
gtk_openmap_proj_normalize_latitude (GtkOpenmapProj *proj)
{
GTK_OPENMAP_PROJ_GET_CLASS (proj)->normalize_latitude (proj);
}
Havoc
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