Get a function reference with decltype(this)

Question

I'm trying to create a macro that will install and remove a Qt event filter constructed from a lambda. In this case, this is known to be a QObject , and thus has a member destroyed . filter is just some QObject -derived event filter. However I have a problem with the line:

connect(this, &decltype(this)::destroyed, [filter]() 
{ 
    qApp->removeEventFilter(filter); 
    filter->deleteLater();
});

which gives the (MSVC2013) error:

left of '::' must be a class, struct or union

Am I just getting the syntax wrong, or can I not do this?

Answer 1

Per @molbdnilo's comment, I wasn't accounting for the fact that this is a pointer. Using a type-trait to remove the pointer made it work:

connect(this, &std::remove_pointer<decltype(this)>::type::destroyed, [filter]() 
{
    qApp->removeEventFilter(filter);
    filter->deleteLater();
});