C++ QgsFeatureRequest函数代码示例

const QgsFeature* QgsActionMenu::feature()
{
  if ( !mFeature || !mFeature->isValid() )
  {
    QgsFeature* feat = new QgsFeature();
    if ( mActions->layer()->getFeatures( QgsFeatureRequest( mFeatureId ) ).nextFeature( *feat ) )
    {
      mFeature = feat;
      mOwnsFeature = true;
    }
    else
    {
      delete feat;
    }
  }

  return mFeature;
}

QgsFeature QgsRelationReferenceWidget::referencedFeature()
{
  QgsFeature f;
  if ( mReferencedLayer )
  {
    QgsFeatureId fid;
    if ( mReadOnlySelector )
    {
      fid = mFeatureId;
    }
    else
    {
      fid = mComboBox->itemData( mComboBox->currentIndex() ).value<QgsFeatureId>();
    }
    mReferencedLayer->getFeatures( QgsFeatureRequest().setFilterFid( fid ) ).nextFeature( f );
  }
  return f;
}

void QgsSelectedFeature::updateGeometry( const QgsGeometry *geom )
{
  delete mGeometry;

  if ( !geom )
  {
    QgsFeature f;
    mVlayer->getFeatures( QgsFeatureRequest().setFilterFid( mFeatureId ) ).nextFeature( f );
    if ( f.hasGeometry() )
      mGeometry = new QgsGeometry( f.geometry() );
    else
      mGeometry = new QgsGeometry();
  }
  else
  {
    mGeometry = new QgsGeometry( *geom );
  }
}

QgsFeature QgsRelationReferenceWidget::referencedFeature() const
{
  QgsFeature f;
  if ( mReferencedLayer )
  {
    QgsFeatureId fid;
    if ( mReadOnlySelector )
    {
      fid = mFeature.id();
    }
    else
    {
      fid = mComboBox->currentData( QgsAttributeTableModel::FeatureIdRole ).value<QgsFeatureId>();
    }
    mReferencedLayer->getFeatures( QgsFeatureRequest().setFilterFid( fid ) ).nextFeature( f );
  }
  return f;
}

QgsFeature QgsRelationReferenceWidget::referencedFeature() const
{
  QgsFeature f;
  if ( mReferencedLayer )
  {
    QgsFeatureRequest request;
    if ( mReadOnlySelector )
    {
      request = QgsFeatureRequest().setFilterFid( mFeature.id() );
    }
    else
    {
      request = mComboBox->currentFeatureRequest();
    }
    mReferencedLayer->getFeatures( request ).nextFeature( f );
  }
  return f;
}

int QgsVectorLayerEditUtils::translateFeature( QgsFeatureId featureId, double dx, double dy )
{
  if ( !mLayer->isSpatial() )
    return 1;

  QgsFeature f;
  if ( !mLayer->getFeatures( QgsFeatureRequest().setFilterFid( featureId ).setSubsetOfAttributes( QgsAttributeList() ) ).nextFeature( f ) || !f.hasGeometry() )
    return 1; //geometry not found

  QgsGeometry geometry = f.geometry();

  int errorCode = geometry.translate( dx, dy );
  if ( errorCode == 0 )
  {
    mLayer->editBuffer()->changeGeometry( featureId, geometry );
  }
  return errorCode;
}

bool QgsLayoutAtlas::prepareForFeature( const int featureI )
{
  if ( !mCoverageLayer )
  {
    return false;
  }

  if ( mFeatureIds.isEmpty() )
  {
    emit messagePushed( tr( "No matching atlas features" ) );
    return false;
  }

  if ( featureI >= mFeatureIds.size() )
  {
    return false;
  }

  mCurrentFeatureNo = featureI;

  // retrieve the next feature, based on its id
  if ( !mCoverageLayer->getFeatures( QgsFeatureRequest().setFilterFid( mFeatureIds[ featureI ].first ) ).nextFeature( mCurrentFeature ) )
    return false;

  mLayout->reportContext().blockSignals( true ); // setFeature emits changed, we don't want 2 signals
  mLayout->reportContext().setLayer( mCoverageLayer.get() );
  mLayout->reportContext().blockSignals( false );
  mLayout->reportContext().setFeature( mCurrentFeature );

  // must come after we've set the report context feature, or the expression context will have an outdated atlas feature
  QgsExpressionContext expressionContext = createExpressionContext();

  // generate filename for current feature
  if ( !evalFeatureFilename( expressionContext ) )
  {
    //error evaluating filename
    return false;
  }

  emit featureChanged( mCurrentFeature );
  emit messagePushed( QString( tr( "Atlas feature %1 of %2" ) ).arg( featureI + 1 ).arg( mFeatureIds.size() ) );

  return mCurrentFeature.isValid();
}

QgsGeometry* QgsTransectSample::findBaselineGeometry( QVariant strataId )
{
  if ( !mBaselineLayer )
  {
    return 0;
  }

  QgsFeatureIterator baseLineIt = mBaselineLayer->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QStringList( mBaselineStrataId ), mBaselineLayer->pendingFields() ) );
  QgsFeature fet;

  while ( baseLineIt.nextFeature( fet ) ) //todo: cache this in case there are many baslines
  {
    if ( strataId == fet.attribute( mBaselineStrataId ) || mShareBaseline )
    {
      Q_NOWARN_DEPRECATED_PUSH
      return fet.geometryAndOwnership();
      Q_NOWARN_DEPRECATED_POP
    }
  }

void QgsSizeScaleWidget::computeFromLayerTriggered()
{
  if ( !mLayer )
    return;

  QgsExpression expression( mExpressionWidget->currentField() );

  QgsExpressionContext context;
  context << QgsExpressionContextUtils::globalScope()
  << QgsExpressionContextUtils::projectScope()
  << QgsExpressionContextUtils::atlasScope( 0 )
  << QgsExpressionContextUtils::layerScope( mLayer );

  if ( ! expression.prepare( &context ) )
    return;

  QStringList lst( expression.referencedColumns() );

  QgsFeatureIterator fit = mLayer->getFeatures(
                             QgsFeatureRequest().setFlags( expression.needsGeometry()
                                                           ? QgsFeatureRequest::NoFlags
                                                           : QgsFeatureRequest::NoGeometry )
                             .setSubsetOfAttributes( lst, mLayer->fields() ) );

  // create list of non-null attribute values
  double min = DBL_MAX;
  double max = -DBL_MAX;
  QgsFeature f;
  while ( fit.nextFeature( f ) )
  {
    bool ok;
    context.setFeature( f );
    const double value = expression.evaluate( &context ).toDouble( &ok );
    if ( ok )
    {
      max = qMax( max, value );
      min = qMin( min, value );
    }
  }
  minValueSpinBox->setValue( min );
  maxValueSpinBox->setValue( max );
  updatePreview();
}

QgsGeometry QgsTransectSample::findBaselineGeometry( const QVariant& strataId )
{
  if ( !mBaselineLayer )
  {
    return QgsGeometry();
  }

  QgsFeatureIterator baseLineIt = mBaselineLayer->getFeatures( QgsFeatureRequest().setSubsetOfAttributes( QStringList( mBaselineStrataId ), mBaselineLayer->fields() ) );
  QgsFeature fet;

  while ( baseLineIt.nextFeature( fet ) ) //todo: cache this in case there are many baslines
  {
    if ( strataId == fet.attribute( mBaselineStrataId ) || mShareBaseline )
    {
      return fet.geometry();
    }
  }
  return QgsGeometry();
}

bool QgsFeaturePool::get( const QgsFeatureId& id , QgsFeature& feature )
{
  QMutexLocker lock( &mLayerMutex );
  QgsFeature* pfeature = mFeatureCache.object( id );
  if ( pfeature == 0 )
  {
    // Get new feature
    pfeature = new QgsFeature();
    // TODO: avoid always querying all attributes (attribute values are needed when merging by attribute)
    if ( !mLayer->getFeatures( QgsFeatureRequest( id ) ).nextFeature( *pfeature ) )
    {
      delete pfeature;
      return false;
    }
    mFeatureCache.insert( id, pfeature );
  }
  feature = *pfeature;
  return true;
}

void QgsAttributeTypeDialog::defaultExpressionChanged()
{
  QString expression = mExpressionWidget->expression();
  if ( expression.isEmpty() )
  {
    mDefaultPreviewLabel->setText( QString() );
    return;
  }

  QgsExpressionContext context = mLayer->createExpressionContext();

  if ( !mPreviewFeature.isValid() )
  {
    // get first feature
    QgsFeatureIterator it = mLayer->getFeatures( QgsFeatureRequest().setLimit( 1 ) );
    it.nextFeature( mPreviewFeature );
  }

  context.setFeature( mPreviewFeature );

  QgsExpression exp = QgsExpression( expression );
  exp.prepare( &context );

  if ( exp.hasParserError() )
  {
    mDefaultPreviewLabel->setText( "<i>" + exp.parserErrorString() + "</i>" );
    return;
  }

  QVariant val = exp.evaluate( &context );
  if ( exp.hasEvalError() )
  {
    mDefaultPreviewLabel->setText( "<i>" + exp.evalErrorString() + "</i>" );
    return;
  }

  QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( editorWidgetType() );

  QString previewText = fieldFormatter->representValue( mLayer, mFieldIdx, editorWidgetConfig(), QVariant(), val );

  mDefaultPreviewLabel->setText( "<i>" + previewText + "</i>" );
}

void QgsRubberSelectId::addFeature( QgsVectorLayer* lyr, QgsFeatureId fid )
{
  if ( mGeometryType != lyr->geometryType() )
  {
    reset();
    mGeometryType = lyr->geometryType();
    mRubberBand->reset( lyr->geometryType() );
    setStyle();
  }
  QgsFeature feat;
  if ( !lyr->getFeatures( QgsFeatureRequest().setFilterFid( fid ).setSubsetOfAttributes( QgsAttributeList() ) ).nextFeature( feat ) )
  {
    return;
  }
  if ( !feat.hasGeometry() )
  {
    return;
  }
  mRubberBand->setToGeometry( feat.geometry(), lyr );
} // void QgsRubberSelectId::addFeature( QgsVectorLayer* mLayer, int Id )

void QgsOfflineEditing::applyFeaturesAdded( QgsVectorLayer* offlineLayer, QgsVectorLayer* remoteLayer, sqlite3* db, int layerId )
{
  QString sql = QString( "SELECT \"fid\" FROM 'log_added_features' WHERE \"layer_id\" = %1" ).arg( layerId );
  QList<int> newFeatureIds = sqlQueryInts( db, sql );

  // get new features from offline layer
  QgsFeatureList features;
  for ( int i = 0; i < newFeatureIds.size(); i++ )
  {
    QgsFeature feature;
    if ( offlineLayer->getFeatures( QgsFeatureRequest().setFilterFid( newFeatureIds.at( i ) ) ).nextFeature( feature ) )
    {
      features << feature;
    }
  }

  // copy features to remote layer
  emit progressModeSet( QgsOfflineEditing::AddFeatures, features.size() );

  int i = 1;
  int newAttrsCount = remoteLayer->pendingFields().count();
  for ( QgsFeatureList::iterator it = features.begin(); it != features.end(); ++it )
  {
    QgsFeature f = *it;

    // NOTE: Spatialite provider ignores position of geometry column
    // restore gap in QgsAttributeMap if geometry column is not last (WORKAROUND)
    QMap<int, int> attrLookup = attributeLookup( offlineLayer, remoteLayer );
    QgsAttributes newAttrs( newAttrsCount );
    QgsAttributes attrs = f.attributes();
    for ( int it = 0; it < attrs.count(); ++it )
    {
      newAttrs[ attrLookup[ it ] ] = attrs[ it ];
    }
    f.setAttributes( newAttrs );

    remoteLayer->addFeature( f, false );

    emit progressUpdated( i++ );
  }
}

QgsFeatureIterator QgsVectorLayerUtils::getValuesIterator( const QgsVectorLayer *layer, const QString &fieldOrExpression, bool &ok, bool selectedOnly )
{
  std::unique_ptr<QgsExpression> expression;
  QgsExpressionContext context;

  int attrNum = layer->fields().lookupField( fieldOrExpression );
  if ( attrNum == -1 )
  {
    // try to use expression
    expression.reset( new QgsExpression( fieldOrExpression ) );
    context.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) );

    if ( expression->hasParserError() || !expression->prepare( &context ) )
    {
      ok = false;
      return QgsFeatureIterator();
    }
  }

  QSet<QString> lst;
  if ( !expression )
    lst.insert( fieldOrExpression );
  else
    lst = expression->referencedColumns();

  QgsFeatureRequest request = QgsFeatureRequest()
                              .setFlags( ( expression && expression->needsGeometry() ) ?
                                         QgsFeatureRequest::NoFlags :
                                         QgsFeatureRequest::NoGeometry )
                              .setSubsetOfAttributes( lst, layer->fields() );

  ok = true;
  if ( !selectedOnly )
  {
    return layer->getFeatures( request );
  }
  else
  {
    return layer->getSelectedFeatures( request );
  }
}