Class: QgsExpressionContextGenerator¶
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.
Note
This is an abstract class, with methods which must be implemented by a subclass.
The following methods must be implemented: createExpressionContext()
Class Hierarchy¶
Subclasses¶
Represents a vector layer which manages a vector based dataset. |
|
Base class for layouts, which can contain items such as maps, labels, scalebars, etc. |
|
Used to render |
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A base class for objects which belong to a layout. |
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Encapsulates a QGIS project, including sets of map layers and their styles, layouts, annotations, canvases, etc. |
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Base class for renderer settings widgets. |
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A widget wrapper for Processing parameter value widgets. |
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Base class for widgets which allow control over the properties of |
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Map canvas is a class for displaying all GIS data types on a canvas. |
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Base class for widgets which configure editor widget types. |
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A widget which allows configuration of the properties of a single |
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Abstract base class for widgets which allow users to specify the properties of a Processing parameter. |
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A configuration widget for processing algorithms allows providing additional configuration options directly on algorithm level, in addition to parameters. |
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A widget for customising the value of Processing algorithm parameters inside a Processing model. |
|
A widget for customizing text formatting settings. |
|
A widget for configuring the temporal properties for a vector layer. |
Abstract Methods
This method needs to be reimplemented in all classes which implement this interface and return an expression context. |
- class qgis.core.QgsExpressionContextGenerator[source]¶
Bases:
object
- abstract createExpressionContext(self) QgsExpressionContext [source]¶
This method needs to be reimplemented in all classes which implement this interface and return an expression context.
- Return type: