Hi,

The QObject class is not copyable for several reasons which are core to Qt:

 http://doc.qt.io/qt-5/object.html#identity-vs-value

It is also not movable for similar reasons (parent-child relationships,
signal-slot connections and more). Even if issues like that could be
addressed, it would still break any client code which holds a pointer to
the
object.

So, QObject will remain non-copyable and non-movable until very radical
changes in Qt happen, if ever.

That means we can't fully use AAA fully with Qt code because

 auto o = QObject{};

won't compile.

Creating QObject-derived instances on the stack is very common for some
types, such as QFile:

 http://doc.qt.io/qt-5/qfile.html#reading-files-directly

It should be possible to write

 auto file = QFile("in.txt");

despite the QFile type being non-copyable and non-movable.

Are there any existing proposals to allow that, or would such a proposal
have any merit?

Thanks,

Steve.

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.

On 23 March 2016 at 07:58, Stephen Kelly <steveire@gmail.com> wrote:
> Hi,
>
> The QObject class is not copyable for several reasons which are core to Qt:
>
>  http://doc.qt.io/qt-5/object.html#identity-vs-value
>
> It is also not movable for similar reasons (parent-child relationships,
> signal-slot connections and more). Even if issues like that could be
> addressed, it would still break any client code which holds a pointer to
> the
> object.
>
> So, QObject will remain non-copyable and non-movable until very radical
> changes in Qt happen, if ever.
>
> That means we can't fully use AAA fully with Qt code because
>
>  auto o = QObject{};
>
> won't compile.
>
> Creating QObject-derived instances on the stack is very common for some
> types, such as QFile:
>
>  http://doc.qt.io/qt-5/qfile.html#reading-files-directly
>
> It should be possible to write
>
>  auto file = QFile("in.txt");
>
> despite the QFile type being non-copyable and non-movable.
>
> Are there any existing proposals to allow that, or would such a proposal
> have any merit?

See http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/p0135r0.html.
It has been accepted
by EWG for C++17.

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.

Ville Voutilainen wrote:

>> Are there any existing proposals to allow that, or would such a proposal
>> have any merit?
>
> See http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/p0135r0.html.
> It has been accepted
> by EWG for C++17.

Great, thanks!

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.