Rupert Swarbrick wrote:
>I've seen various "inaccessible base errors" in searching on Google, but
>I couldn't quite find this one and I don't understand quite what's going on.
>
>I have a class, FileEntry (which consists of an entry widget and a
>button that spawns a file selection dialog from Gtkmm):
>
>class FileEntry : protected Gtk::HBox
>{
>public:
> FileEntry(bool open=true,
> std::string defaultname="");
>protected:
> void on_button();
> ...stuff...
>};
>
>(Note that it inherits from _protected_ HBox)
>
>Now, in FileEntry::FileEntry, I need to connect the button clicked event
>for said button to a handler. Thus I create the slot with this line:
>
>sigc::slot<void> sl = sigc::mem_fun(*this, &FileEntry::on_button);
>
>Sadly, I now get these g++ error:
>
>/usr/include/sigc++-2.0/sigc++/type_traits.h: In instantiation of 'const
>bool sigc::is_base_and_derived<sigc::trackable, rjs::FileEntry>::value':
>/usr/include/sigc++-2.0/sigc++/functors/mem_fun.h:1792: instantiated
>from 'sigc::bound_mem_functor0<void, rjs::FileEntry>'
>FileEntry.cc:11: instantiated from here
>/usr/include/sigc++-2.0/sigc++/type_traits.h:132: error:
>'sigc::trackable' is an inaccessible base of 'rjs::FileEntry'
>
>Now then, I can compile happily by inheriting from public Gtk::HBox, but
>this really doesn't seem like it should be necessary - surely as we're
>in the constructor the public/private/whatever should make no difference?
>
>I'd really like to know what the heck's going on here - does mem_fun do
>something very wierd?
>
>
Please, consider my answer like a guess.
"sigc::mem_fun" is a wrapper that construct sigc::slot object. Last one
should have public access to your object sigc::trackable destructor to
disconnect slot/signals when your object destroyed. Probably, you better
do investigate source codes either documentation files for more information.
Regards,
-andrew
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