Class: QgsExpressionFieldBuffer

class qgis.core.QgsExpressionFieldBuffer

Bases: sip.wrapper

Constructor for QgsExpressionFieldBuffer.

QgsExpressionFieldBuffer(QgsExpressionFieldBuffer)

Buffers information about expression fields for a vector layer.

Methods

addExpression

Add an expression to the buffer

expressions

rtype

object

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

class ExpressionField(exp: str, fld: QgsField)

Bases: sip.wrapper

QgsExpressionFieldBuffer.ExpressionField(QgsExpressionFieldBuffer.ExpressionField)

Parameters
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) → object
Return type

object

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) –