[Qgis-developer] Problems using QgsVectorLayer::selectedFeatures()

[Federico J. Fernández]

>
> I'm confused - you don't have to allocate any pointers for the list.
> The QList class uses implicit sharing of data (like many other qt
> classes), so the list can be passed by value very cheaply. Please
> paste the code of the whole method if it's not too long and indicate
> on what line the application crashes.
>

Hi Martin,

Thanks for your help. Here is the relevant code:

void MainWindow::mergeFeatures(void)
{
    if ( !this->currentLayer ) {
        QMessageBox::information( 0, tr( "Active layer is not vector" ), tr(
"The merge features tool only works on vector layers. Please select a vector
layer from the layer list" ) );
        return;
    }

    this->developmentsLayer->startEditing();

    if ( !this->developmentsLayer->isEditable() ) {
        QMessageBox::information( 0, tr( "Layer not editable" ), tr(
"Merging features can only be done for layers in editing mode. To use the
merge tool, go to  Layer->Toggle editing" ) );
        return;
    }

    const QgsFeatureIds &featureIdSet =
this->currentLayer->selectedFeaturesIds();
    if ( featureIdSet.size() < 2 ) {
        QMessageBox::information( 0, tr( "Not enough features selected" ),
tr( "The merge tool requires at least two selected features" ) );
        return;
    }

    //get initial selection (may be altered by attribute merge dialog later)
    QgsFeatureList &featureList = this->currentLayer->selectedFeatures();
//get QList<QgsFeature>
    bool canceled;
    QgsGeometry* unionGeom = unionGeometries( this->currentLayer,
featureList, canceled );
    if(!unionGeom) {
        if (!canceled) {
            QMessageBox::critical( 0, tr( "Merge failed" ), tr( "An error
occured during the merge operation" ) );
        }
        return;
    }

    this->developmentsLayer->beginEditCommand( tr( "Merged features" ) );

  //create new feature
  QgsFeature newFeature;
  newFeature.setGeometry( unionGeom );

  this->developmentsLayer->addFeature( newFeature, false );

  this->statusBar()->showMessage( tr("Saving new Development Project..."));

  this->developmentsLayer->endEditCommand();
  this->developmentsLayer->commitChanges();

  this->currentLayer->removeSelection();

  this->statusBar()->showMessage( tr("Project saved."));
}

Then, at method end, it yields:

Debug Assertion Failed!
>
> File: dbgdel.cpp, Line: 52
> Expression: _BLOCK_TYPE_IS_VALID(pHead->nBlockUse)
>

The backtrace shows the call to ~QList() as one of the last frames.

Thanks again..!

--
fede
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/qgis-developer/attachments/20110207/ed7e7c97/attachment.html