[Qt-interest] deleteLater() for QGraphicsItem

[Daniel Price]

You are most welcome :)

> -----Original Message-----
> From: Andreas Unger [mailto:andi.unger05 at gmail.com]
> Sent: 03 December 2009 20:22
> To: Daniel Price
> Cc: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] deleteLater() for QGraphicsItem
>
>
>
> On Thu, Dec 3, 2009 at 4:19 AM, Daniel Price <daniel.price at fxhome.com>
> wrote:
>
>
>       We hit the same problem but there is a really simply solution -
> when you remove the item from the scene, wrap the pointer to in a
> QObject-derived class which calls deleteLater() in the constructor.
> Create this object on the heap with new() but ignore the return
> pointer. In the destructor, delete the graphics item. Here's my
> templated version that can be used with any type:
>
>
>
>       #include <QObject>
>
>
>
>       template <typename T>
>
>       class DelayedDelete : public QObject
>
>       {
>
>       public:
>
>                       explicit DelayedDelete(T *&item) : m_item(item)
>
>                       {
>
>                                       item = 0;
>
>                                       deleteLater();
>
>                       }
>
>                       virtual ~DelayedDelete()
>
>                       {
>
>                                       delete m_item;
>
>                       }
>
>       private:
>
>                       T *m_item;
>
>       };
>
>
>
>       You'll notice that the constructor takes a reference to the
> original pointer which it sets to 0 after copying it in the initialize
> list - this avoid leaving a hanging pointer in the calling code which
> DelayedDelete has taken ownership of. Here's how it's called:
>
>
>
>       scene->removeItem(gfxItem);
>
>       new DelayedDelete<RectItem>(gfxItem); // would have crashed if
> gfxItem was deleted here
>
>
>
>       Where RectItem is my QGraphicsItem-derived class. As you can see
> it's fire-and-forget. Qt will delete the DelayedDelete instance during
> the next event loop. But as far as your code is concerned, gfxItem is
> dead.
>
>
> Fantastic! This worked for me.
>
> Thanks a lot,
> Andreas
>
>
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