Richard Heck <[EMAIL PROTECTED]> writes:
| Andre Poenitz wrote:
| > On Thu, May 31, 2007 at 09:12:56PM +0200, Peter Kümmel wrote:
| >
| >>> I tried to do something like this so I didn't have the same code in two
| >>> places:
| >>> QModelIndex & QCitationDialog::getSelectedIndex(QListView *) {
| >>> QModelIndexList const selIdx =
| >>> availableLV->selectionModel()->selectedIndexes();
| >>> if (selIdx.empty())
| >>> return QModelIndex(); //this is an invalid one.
| >>> return selIdx.first();
| >>> }
| >>> But that failed: warning: returns reference to temporary. Any ideas how
| >>> to avoid this and still return a reference? Or could I return a smart
| >>>
| >> returning "const QModelIndex &" should be save. But you could also
| >> return may value, copying QModelIndex isn't that expensive. The Qt
| >> code return often by value, QModelIndex was designed for this.
| >>
| > Apart from that
| >
| > QModelIndex & QCitationDialog::getSelectedIndex(QListView *) {
| > ...
| > if (selIdx.empty())
| > return QModelIndex(); //this is an invalid one.
| >
| > returns a reference to a temporary, which is useless in any case
| > as accessing it will invoke undefined behaviour.
| >
| Yes, the question was how to avoid doing that and still return a
| reference, if there is any such way.
When returning by copy you could give the temporary a name to let the
compiler use NRVO. (Optimization technique used by compilers.)
--
Lgb
