QgsExpressionContextGenerator Class Reference

Abstract interface for generating an expression context. More...

#include <qgsexpressioncontextgenerator.h>

Inheritance diagram for QgsExpressionContextGenerator:

Public Member Functions
virtual	~QgsExpressionContextGenerator ()=default
virtual QgsExpressionContext	createExpressionContext () const =0
	This method needs to be reimplemented in all classes which implement this interface and return an expression context.

Detailed Description

Abstract interface for generating an expression context.

You need to implement this interface in a class and register this class with QgsFieldExpressionWidget::registerExpressionGenerator().

This is used for example in QgsPropertyOverrideButton or QgsFieldExpressionWidget classes which will ask for a new QgsExpressionContext every time the expression editor is opened. This way they are able to provide an up-to-date expression editor even when the environment changes.

Definition at line 35 of file qgsexpressioncontextgenerator.h.

Constructor & Destructor Documentation

~QgsExpressionContextGenerator()

virtual QgsExpressionContextGenerator::~QgsExpressionContextGenerator ( )

virtualdefault

Member Function Documentation

createExpressionContext()

virtual QgsExpressionContext QgsExpressionContextGenerator::createExpressionContext ( ) const

pure virtual

This method needs to be reimplemented in all classes which implement this interface and return an expression context.

Implemented in QgsVectorLayer, QgsExpressionBasedNumericFormatWidget, QgsLayout, QgsLayoutAtlas, QgsLayoutFrame, QgsLayoutItem, QgsLayoutItemAttributeTable, QgsLayoutItemLegend, QgsLayoutItemMap, QgsLayoutItemMapGrid, QgsLayoutItemMapItem, QgsLayoutMultiFrame, QgsLayoutObject, QgsPrintLayout, QgsProject, QgsCalloutWidget, QgsEditorConfigWidget, QgsExternalResourceConfigDlg, QgsLabelSettingsWidgetBase, QgsLayoutAttributeTableWidget, QgsLayoutElevationProfileWidget, QgsLayoutLabelWidget, QgsLayoutManualTableWidget, QgsLayoutScaleBarWidget, QgsNumericFormatWidget, QgsProcessingAlgorithmConfigurationWidget, QgsProcessingModelerParameterWidget, QgsProcessingAbstractParameterDefinitionWidget, QgsAbstractProcessingParameterWidgetWrapper, QgsMapCanvas, QgsTextFormatWidget, QgsVectorLayerTemporalPropertiesWidget, QgsRasterLayerProperties, QgsRasterTransparencyWidget, QgsCategorizedSymbolRendererWidget, QgsEmbeddedSymbolRendererWidget, QgsGraduatedSymbolRendererWidget, QgsHeatmapRendererWidget, QgsLayerPropertiesWidget, QgsPointClusterRendererWidget, QgsPointDisplacementRendererWidget, QgsRendererWidget, QgsSymbolLayerWidget, QgsTableEditorFormattingWidget, QgsAttributeActionPropertiesDialog, QgsAttributesFormProperties, and QgsAttributesDnDTree.

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The documentation for this class was generated from the following file:

• /build/qgis-3.40.0+99sid/src/core/qgsexpressioncontextgenerator.h