QgsExpressionContextGenerator class

Abstract interface for generating an expression context.

Contents

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.

Derived classes

class QgsAbstractProcessingParameterWidgetWrapper
A widget wrapper for Processing parameter value widgets.
class QgsDataDefinedValueDialog
Utility classes for "en masse" size definition.
class QgsEditorConfigWidget
This class should be subclassed for every configurable editor widget type.
class QgsLayout
Base class for layouts, which can contain items such as maps, labels, scalebars, etc.
class QgsLayoutObject
A base class for objects which belong to a layout.
class QgsPointClusterRendererWidget
A widget which allows configuration of the properties for a QgsPointClusterRenderer.
class QgsProcessingModelerParameterWidget
A widget for customising the value of Processing algorithm parameter inside a Processing model.
class QgsProject
Reads and writes project states.
class QgsVectorLayer
Represents a vector layer which manages a vector based data sets.

Public functions

auto createExpressionContext() const -> QgsExpressionContext pure virtual
This method needs to be reimplemented in all classes which implement this interface and return an expression context.

Function documentation

QgsExpressionContext QgsExpressionContextGenerator::createExpressionContext() const pure virtual

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