Class: QgsExpressionFieldBuffer¶
- class qgis.core.QgsExpressionFieldBuffer¶
Bases:
sip.wrapper
Buffers information about expression fields for a vector layer.
New in version 2.6.
QgsExpressionFieldBuffer() Constructor for QgsExpressionFieldBuffer.
QgsExpressionFieldBuffer(
QgsExpressionFieldBuffer
)Methods
Add an expression to the buffer
- rtype:
List[QgsExpressionFieldBuffer.ExpressionField]
Reads expressions from project file
Remove an expression from the buffer
Renames an expression field at a given index
Changes the expression at a given index
Adds fields with the expressions buffered in this object to a
QgsFields
objectSaves expressions to xml under the layer node
- class ExpressionField(exp: str, fld: QgsField)¶
- class ExpressionField(QgsExpressionFieldBuffer.ExpressionField)
Bases:
sip.wrapper
- cachedExpression¶
- field¶
- addExpression(self, exp: str, fld: QgsField)¶
Add an expression to the buffer
- Parameters:
exp (str) – expression to add
fld (QgsField) – field to add
- expressions(self) List[QgsExpressionFieldBuffer.ExpressionField] ¶
- Return type:
- readXml(self, layer_node: QDomNode)¶
Reads expressions from project file
- Parameters:
layer_node (QDomNode) –
- removeExpression(self, index: int)¶
Remove an expression from the buffer
- Parameters:
index (int) – index of expression to remove
- renameExpression(self, index: int, name: str)¶
Renames an expression field at a given index
- Parameters:
index (int) – The index of the expression to change
name (str) – New name for field
New in version 3.0.
- updateExpression(self, index: int, exp: str)¶
Changes the expression at a given index
- Parameters:
index (int) – The index of the expression to change
exp (str) – The new expression to set
New in version 2.9.
- updateFields(self, flds: QgsFields)¶
Adds fields with the expressions buffered in this object to a
QgsFields
object- Parameters:
flds (QgsFields) – The fields to be updated
- writeXml(self, layer_node: QDomNode, document: QDomDocument)¶
Saves expressions to xml under the layer node
- Parameters:
layer_node (QDomNode) –
document (QDomDocument) –