Class: QgsExpressionFieldBuffer

class qgis.core.QgsExpressionFieldBuffer

Bases: sip.wrapper

Constructor for QgsExpressionFieldBuffer.

QgsExpressionFieldBuffer(QgsExpressionFieldBuffer)

Buffers information about expression fields for a vector layer.

New in version 2.6: Enums

Methods

addExpression	Add an expression to the buffer
expressions
readXml	Reads expressions from project file
removeExpression	Remove an expression from the buffer
renameExpression	Renames an expression field at a given index
updateExpression	Changes the expression at a given index
updateFields	Adds fields with the expressions buffered in this object to a QgsFields object
writeXml	Saves expressions to xml under the layer node

Signals

Attributes

class ExpressionField(exp: str, fld: QgsField)

Bases: sip.wrapper

QgsExpressionFieldBuffer.ExpressionField(QgsExpressionFieldBuffer.ExpressionField)

cachedExpression

field

addExpression(self, exp: str, fld: QgsField)

Add an expression to the buffer

Parameters

• exp – expression to add

• fld – field to add

expressions(self) → List[QgsExpressionFieldBuffer.ExpressionField]

readXml(self, layer_node: QDomNode)

Reads expressions from project file

removeExpression(self, index: int)

Remove an expression from the buffer

Parameters

index – index of expression to remove

renameExpression(self, index: int, name: str)

Renames an expression field at a given index

Parameters

• index – The index of the expression to change

• name – New name for field

New in version 3.0.

updateExpression(self, index: int, exp: str)

Changes the expression at a given index

Parameters

• index – The index of the expression to change

• exp – 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 – The fields to be updated

writeXml(self, layer_node: QDomNode, document: QDomDocument)

Saves expressions to xml under the layer node