Class: QgsExpressionFieldBuffer

Buffers information about expression fields for a vector layer.

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

class qgis.core.QgsExpressionFieldBuffer

Bases: object

class ExpressionField(exp: str | None, fld: QgsField)

class ExpressionField(a0: QgsExpressionFieldBuffer.ExpressionField)

Bases: object

cachedExpression

field

addExpression(self, exp: str | None, fld: QgsField)

Add an expression to the buffer

Parameters:

• exp (Optional[str]) – expression to add

• fld (QgsField) – field to add

expressions(self) → List[QgsExpressionFieldBuffer.ExpressionField]

Return type:

List[QgsExpressionFieldBuffer.ExpressionField]

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 | None)

Renames an expression field at a given index

Parameters:

• index (int) – The index of the expression to change

• name (Optional[str]) – New name for field

updateExpression(self, index: int, exp: str | None)

Changes the expression at a given index

Parameters:

• index (int) – The index of the expression to change

• exp (Optional[str]) – The new expression to set

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)