[Qt-interest] About QScopedPointer

[Mihail Naydenov]

----- Original Message ----

> From: Thiago Macieira <thiago at kde.org>
> To: qt-interest at qt.nokia.com
> Sent: Fri, May 13, 2011 12:39:55 PM
> Subject: Re: [Qt-interest] About QScopedPointer
> 
> On Friday, 13 de May de 2011 00:47:56 Mihail Naydenov wrote:
> > I am in a  bit of a struggle how to pass a pointer to a
> > QScopedPointer-managed  pointer.
> > It seems impossible:
> > 
> >  QScopedPointer<Data> d;
> > 
> > fund(void** data);  //<  want to pass d into this
> 
> No, you don't.
> 
> You have a  QScopedPointer<Data>, which is equivalent to Data*. One level of 
> pointer.
> 
> That function takes a void**: two levels of  pointers.
> 
> If you had a simple Data *d; you'd pass &d. That usually  means that the called 
>
> function would modify the pointer.


Problem is sometimes the pointer is not initialized when constructed.

It is later initialized by some func(Data** data)

Now I will have to do

Data* p = NULL;

func(&p);

QScopedPointer<Data, Release> sp(p);

// use sp, forget about p

Which is a bit cumbersome 

> 
> That's a  really bad idea with QScopedPointer. It owns the pointer and you 
> should not  modify the value from underneath it.
> 
> > I guess QScopedPointer lacks a  T*& data() member function. Is this going to
> > be addressed. Or am I  missing something.
> 
> No, it's not going to be addressed. That method can  only be used to allow you 

> to modify the pointer that QScopedPointer tracks  without telling it.
> 
> You chose to use QScopedPointer so it would manage  the pointers for you.
> 
> -- 
> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>   Senior Product  Manager - Nokia, Qt Development Frameworks
>       PGP/GPG:  0x6EF45358; fingerprint:
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>