Class: QgsExpressionNodeCondition¶

An expression node for CASE WHEN clauses.

Class Hierarchy¶

Base classes¶

QgsExpressionNode

Abstract base class for all nodes that can appear in an expression.

Methods

`conditions`	The list of WHEN THEN expression parts of the expression.
`elseExp`	The ELSE expression used for the condition.

Virtual Methods

In PyQGIS, only methods marked as virtual can be safely overridden in a Python subclass of QgsExpressionNodeCondition. See the FAQ for more details.

`evalNode`
`prepareNode`

class qgis.core.QgsExpressionNodeCondition[source]¶

Bases: QgsExpressionNode

__init__(conditions: Iterable[QgsExpressionNodeCondition.WhenThen] | None, elseExp: QgsExpressionNode | None = None)

Create a new node with the given list of conditions and an optional elseExp expression.

Parameters:

conditions (Optional[Iterable[QgsExpressionNodeCondition.WhenThen]])
elseExp (Optional[QgsExpressionNode] = None)

class WhenThen[source]¶

Bases: object

Represents a “WHEN… THEN…” portation of a CASE WHEN clause in an expression.

QgsExpressionNodeCondition.WhenThen(whenExp: Optional[QgsExpressionNode], thenExp: Optional[QgsExpressionNode]) A combination of when and then. Simple as that.

thenExp(self) → QgsExpressionNode | None[source]¶

The expression node that makes the THEN result part of the condition.

Return type:: Optional[QgsExpressionNode]
Returns:: The expression node that makes the THEN result part of the condition.

whenExp(self) → QgsExpressionNode | None[source]¶

The expression that makes the WHEN part of the condition.

Return type:: Optional[QgsExpressionNode]
Returns:: The expression node that makes the WHEN part of the condition check.

conditions(self) → List[QgsExpressionNodeCondition.WhenThen][source]¶

The list of WHEN THEN expression parts of the expression.

Return type:: List[QgsExpressionNodeCondition.WhenThen]
Returns:: The list of WHEN THEN expression parts of the expression.

elseExp(self) → QgsExpressionNode | None[source]¶

The ELSE expression used for the condition.

Return type:: Optional[QgsExpressionNode]
Returns:: The ELSE expression used for the condition.

virtual evalNode(self, parent: QgsExpression | None, context: QgsExpressionContext | None) → Any[source]¶

Parameters:

parent (Optional[QgsExpression])
context (Optional[QgsExpressionContext])

Return type:

Any

virtual prepareNode(self, parent: QgsExpression | None, context: QgsExpressionContext | None) → bool[source]¶

Parameters:

parent (Optional[QgsExpression])
context (Optional[QgsExpressionContext])

Return type:

bool