Subgroup: Default
Class: QgsDefaultValue¶
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class
qgis.core.
QgsDefaultValue
¶ Bases:
sip.wrapper
The QgsDefaultValue class provides a container for managing clientside default values for fields.
A QgsDefaultValue consists of an expression string that will be evaluated on the client when a defeault field value needs to be generated.
Usual values for such an expression are
- now() for a timestamp for a record
- @some_variable to insert a project or application level variable like
the username of the one digitizing a feature - $length to insert a derived attribute of a geometry
QgsDefaultValue also has a applyOnUpdate flag which will indicate that a default value should also be applied when a feature is updated. If this is not set, the default value will only be used when a feature is created.
New in version 3.0: Methods
applyOnUpdate
The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it’s created. expression
The expression will be evaluated whenever a default value needs to be calculated for a field. isValid
Returns if this default value should be applied. setApplyOnUpdate
The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it’s created. setExpression
The expression will be evaluated whenever a default value needs to be calculated for a field. Attributes
-
applyOnUpdate
(self) → bool¶ The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it’s created.
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expression
(self) → str¶ The expression will be evaluated whenever a default value needs to be calculated for a field.
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isValid
(self) → bool¶ Returns if this default value should be applied.
Returns: false if the expression is a null string.
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setApplyOnUpdate
(self, applyOnUpdate: bool)¶ The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it’s created.
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setExpression
(self, expression: str)¶ The expression will be evaluated whenever a default value needs to be calculated for a field.