[Development] Allowed C++11 features [was: Re: Re: MSVC2012 in CI]

[Marc Mutz]

On Monday 21 March 2016 13:18:18 Sean Harmer wrote:
> On Monday 21 March 2016 12:44:34 Marc Mutz wrote:
> > On Monday 21 March 2016 12:07:24 Poenitz Andre wrote:
> > > Marc Mutz <marc.mutz at kdab.com> wrote:
> > > > I said then and I repeat it now that imho template aliases are not
> > > > interesting for library development. In particular, I don't think
> > > > something like
> > > > 
> > > > > > > template<typename T>
> > > > > > > using QNodeCreatedChangePtr =
> > > > > > > QSharedPointer<QNodeCreatedChange<T>>;
> > > > 
> > > > should be part of an API of a library. We have auto to avoid having
> > > > to type this type. The typedefs just hide the (essential) fact that
> > > > this is a shared pointer type.
> > > 
> > > Do I understand correctly that you argue that the fact that the actual
> > > type is a shared pointer is so important that it shall not be hidden by
> > > a template alias whereas it would be completely fine to hide everything
> > > related to type by using auto?
> > 
> > Yes, you understood me correctly.
> > 
> > And to answer your implied objection, too:
> > 
> > No, there's no contradiction, because auto is for use in implementations
> > and I was talking explicitly about APIs (which implies API
> > documentation, too). It's one thing to write
> > 
> >     auto o = factory->create();
> > 
> > and quite another to have
> > 
> >    QNodeCreatedChangePtr<Foo> create() [virtual]
> > 
> > (to make up a plausible, but nonsensical example) in the docs.
> 
> I'm actually after the implementation case here so I can write:
> 
> auto creationChange = QNodeCreatedChangePtr<QEntityData>::create(this);
> 
> rather than:
> 
> auto creationChange = QSharedPointer<QNodeCreatedChange<QEntityData>
> >::create(this);

In this case, my argument is moot, of course. If you don't want to wait for 
the CI to drop MSVC 2012, you can just use a struct:

  template <typename T>
  struct QNodeCreatedChangePtr {
      static QSharedPointer<QNodeCreatedChange<T> > create()
      { return QSharedPointer<QNodeCreatedChange<T> >::create(); }
  };

> Of course it would also be a convenience to the user when they need to do
> similar. I guess I'll redo my changes if I can't use template aliases like
> this unconditionally.
> 
> Cheers,
> 
> Sean

-- 
Marc Mutz <marc.mutz at kdab.com> | Senior Software Engineer
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