avoid detach when looping on fields and convert some Q_FOREACH (#7905)

* avoid detach when looping on fields and convert some Q_FOREACH

* fields already exist

Author: 3nids

src/app/qgsattributetabledialog.cpp

@@ -108,7 +108,8 @@ QgsAttributeTableDialog::QgsAttributeTableDialog( QgsVectorLayer *layer, QgsAttr
   connect( mActionExpressionSelect, &QAction::triggered, this, &QgsAttributeTableDialog::mActionExpressionSelect_triggered );
   connect( mMainView, &QgsDualView::showContextMenuExternally, this, &QgsAttributeTableDialog::showContextMenu );
 
-  Q_FOREACH ( const QgsField &field, mLayer->fields() )
+  const QgsFields fields = mLayer->fields();
+  for ( const QgsField &field : fields )
   {
     mVisibleFields.append( field.name() );
   }

src/core/qgsjsonutils.cpp

@@ -175,7 +175,8 @@ QString QgsJsonExporter::exportFeature( const QgsFeature &feature, const QVarian
           QgsFeatureIterator it = childLayer->getFeatures( req );
           QVector<QVariant> attributeWidgetCaches;
           int fieldIndex = 0;
-          for ( const auto &field : childLayer->fields() )
+          const QgsFields fields = childLayer->fields();
+          for ( const QgsField &field : fields )
           {
             QgsEditorWidgetSetup setup = field.editorWidgetSetup();
             QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );

src/core/qgsvectorlayereditbuffer.cpp

@@ -256,7 +256,8 @@ bool QgsVectorLayerEditBuffer::addAttribute( const QgsField &field )
   if ( field.name().isEmpty() )
     return false;
 
-  Q_FOREACH ( const QgsField &updatedField, L->fields() )
+  const QgsFields fields = L->fields();
+  for ( const QgsField &updatedField : fields )
   {
     if ( updatedField.name() == field.name() )
       return false;
@@ -303,7 +304,8 @@ bool QgsVectorLayerEditBuffer::renameAttribute( int index, const QString &newNam
   if ( index < 0 || index >= L->fields().count() )
     return false;
 
-  Q_FOREACH ( const QgsField &updatedField, L->fields() )
+  const QgsFields fields = L->fields();
+  for ( const QgsField &updatedField : fields )
   {
     if ( updatedField.name() == newName )
       return false;

src/gui/qgsnewauxiliarylayerdialog.cpp

@@ -27,7 +27,8 @@ QgsNewAuxiliaryLayerDialog::QgsNewAuxiliaryLayerDialog( QgsVectorLayer *layer, Q
 {
   setupUi( this );
 
-  for ( const QgsField &field : mLayer->fields() )
+  const QgsFields fields = mLayer->fields();
+  for ( const QgsField &field : fields )
     comboBox->addItem( field.name() );
 }
 

src/gui/qgspropertyoverridebutton.cpp

@@ -155,7 +155,8 @@ void QgsPropertyOverrideButton::updateFieldLists()
   if ( mVectorLayer )
   {
     // store just a list of fields of unknown type or those that match the expected type
-    Q_FOREACH ( const QgsField &f, mVectorLayer->fields() )
+    const QgsFields fields = mVectorLayer->fields();
+    for ( const QgsField &f : fields )
     {
       bool fieldMatch = false;
       QString fieldType;

src/gui/symbology/qgsvectorfieldsymbollayerwidget.cpp

@@ -39,7 +39,8 @@ QgsVectorFieldSymbolLayerWidget::QgsVectorFieldSymbolLayerWidget( QgsVectorLayer
     mXAttributeComboBox->addItem( QString() );
     mYAttributeComboBox->addItem( QString() );
     int i = 0;
-    Q_FOREACH ( const QgsField &f, vectorLayer()->fields() )
+    const QgsFields fields = vectorLayer()->fields();
+    for ( const QgsField &f : fields )
     {
       QString fieldName = f.name();
       mXAttributeComboBox->addItem( vectorLayer()->fields().iconForField( i ), fieldName );

src/providers/virtual/qgsvirtuallayersourceselect.cpp

@@ -300,7 +300,8 @@ void QgsVirtualLayerSourceSelect::updateLayersList()
     {
       apis->add( l->name() );
       QgsVectorLayer *vl = static_cast<QgsVectorLayer *>( l );
-      Q_FOREACH ( const QgsField &f, vl->fields().toList() )
+      const QgsFields fields = vl->fields();
+      for ( const QgsField &f : fields )
       {
         apis->add( f.name() );
       }

src/server/services/wms/qgswmsrenderer.cpp

@@ -1459,7 +1459,7 @@ namespace QgsWms
     mAccessControl->filterFeatures( layer, fReq );
 
     QStringList attributes;
-    for ( const QgsField &field : layer->fields().toList() )
+    for ( const QgsField &field : fields )
     {
       attributes.append( field.name() );
     }