An expression node for CASE WHEN clauses. More...

#include <qgsexpressionnodeimpl.h>

Inheritance diagram for QgsExpressionNodeCondition:

Classes
class	WhenThen
	Represents a "WHEN... THEN..." portation of a CASE WHEN clause in an expression. More...

Public Types
typedef QList< QgsExpressionNodeCondition::WhenThen * >	WhenThenList

Public Types inherited from QgsExpressionNode
enum	NodeType { ntUnaryOperator , ntBinaryOperator , ntInOperator , ntFunction , ntLiteral , ntColumnRef , ntCondition , ntIndexOperator , ntBetweenOperator }
	Known node types. More...

Public Member Functions
	QgsExpressionNodeCondition (const QgsExpressionNodeCondition::WhenThenList &conditions, QgsExpressionNode *elseExp=nullptr)
	Create a new node with the given list of conditions and an optional elseExp expression.

	QgsExpressionNodeCondition (QgsExpressionNodeCondition::WhenThenList conditions, QgsExpressionNode elseExp=nullptr)
	Create a new node with the given list of conditions and an optional elseExp expression.

	~QgsExpressionNodeCondition () override

QgsExpressionNode *	clone () const override
	Generate a clone of this node.

WhenThenList	conditions () const
	The list of WHEN THEN expression parts of the expression.

QString	dump () const override
	Dump this node into a serialized (part) of an expression.

QgsExpressionNode *	elseExp () const
	The ELSE expression used for the condition.

QVariant	evalNode (QgsExpression parent, const QgsExpressionContext context) override
	Abstract virtual eval method Errors are reported to the parent.

bool	isStatic (QgsExpression parent, const QgsExpressionContext context) const override
	Returns `true` if this node can be evaluated for a static value.

bool	needsGeometry () const override
	Abstract virtual method which returns if the geometry is required to evaluate this expression.

QList< const QgsExpressionNode * >	nodes () const override
	Returns a list of all nodes which are used in this expression.

QgsExpressionNode::NodeType	nodeType () const override
	Gets the type of this node.

bool	prepareNode (QgsExpression parent, const QgsExpressionContext context) override
	Abstract virtual preparation method Errors are reported to the parent.

QSet< QString >	referencedColumns () const override
	Abstract virtual method which returns a list of columns required to evaluate this node.

QSet< QString >	referencedFunctions () const override
	Returns a set of all functions which are used in this expression.

QSet< QString >	referencedVariables () const override
	Returns a set of all variables which are used in this expression.

Public Member Functions inherited from QgsExpressionNode
virtual	~QgsExpressionNode ()=default

QVariant	cachedStaticValue () const
	Returns the node's static cached value.

const QgsExpressionNode *	effectiveNode () const
	Returns a reference to the simplest node which represents this node, after any compilation optimizations have been applied.

QVariant	eval (QgsExpression parent, const QgsExpressionContext context)
	Evaluate this node with the given context and parent.

bool	hasCachedStaticValue () const
	Returns `true` if the node can be replaced by a static cached value.

bool	prepare (QgsExpression parent, const QgsExpressionContext context)
	Prepare this node for evaluation.

void	setCachedStaticValue (const QVariant &value) const
	Sets the cached static value for the node.

Additional Inherited Members
Public Attributes inherited from QgsExpressionNode
int	parserFirstColumn = 0
	First column in the parser this node was found.

int	parserFirstLine = 0
	First line in the parser this node was found.

int	parserLastColumn = 0
	Last column in the parser this node was found.

int	parserLastLine = 0
	Last line in the parser this node was found.

Protected Member Functions inherited from QgsExpressionNode
	QgsExpressionNode ()=default

	QgsExpressionNode (const QgsExpressionNode &other)

void	cloneTo (QgsExpressionNode *target) const
	Copies the members of this node to the node provided in target.

QgsExpressionNode &	operator= (const QgsExpressionNode &other)

Protected Attributes inherited from QgsExpressionNode
QVariant	mCachedStaticValue
	Contains the static, precalculated value for the node if mHasCachedValue is `true`.

std::unique_ptr< QgsExpressionNode >	mCompiledSimplifiedNode
	Contains a compiled node which represents a simplified version of this node as a result of compilation optimizations.

bool	mHasCachedValue = false
	`true` if the node has a static, precalculated value.

Detailed Description

An expression node for CASE WHEN clauses.

Definition at line 560 of file qgsexpressionnodeimpl.h.

Member Typedef Documentation

◆ WhenThenList

typedef QList<QgsExpressionNodeCondition::WhenThen *> QgsExpressionNodeCondition::WhenThenList

Definition at line 608 of file qgsexpressionnodeimpl.h.

Constructor & Destructor Documentation

◆ QgsExpressionNodeCondition() [1/2]

QgsExpressionNodeCondition::QgsExpressionNodeCondition	(	QgsExpressionNodeCondition::WhenThenList *	conditions,
		QgsExpressionNode *	elseExp = `nullptr`
	)

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

Definition at line 1711 of file qgsexpressionnodeimpl.cpp.

◆ QgsExpressionNodeCondition() [2/2]

QgsExpressionNodeCondition::QgsExpressionNodeCondition	(	const QgsExpressionNodeCondition::WhenThenList &	conditions,
		QgsExpressionNode *	elseExp = `nullptr`
	)

inline

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

Definition at line 618 of file qgsexpressionnodeimpl.h.

◆ ~QgsExpressionNodeCondition()

QgsExpressionNodeCondition::~QgsExpressionNodeCondition ( )

override

Definition at line 1718 of file qgsexpressionnodeimpl.cpp.

Member Function Documentation

◆ clone()

QgsExpressionNode * QgsExpressionNodeCondition::clone ( ) const

overridevirtual

Generate a clone of this node.

Ownership is transferred to the caller.

Returns: a deep copy of this node.

Implements QgsExpressionNode.

Definition at line 1900 of file qgsexpressionnodeimpl.cpp.

◆ conditions()

WhenThenList QgsExpressionNodeCondition::conditions ( ) const

inline

The list of WHEN THEN expression parts of the expression.

Returns: The list of WHEN THEN expression parts of the expression.

Definition at line 634 of file qgsexpressionnodeimpl.h.

◆ dump()

QString QgsExpressionNodeCondition::dump ( ) const

overridevirtual

Dump this node into a serialized (part) of an expression.

The returned expression does not necessarily literally match the original expression, it's just guaranteed to behave the same way.

Implements QgsExpressionNode.

Definition at line 1815 of file qgsexpressionnodeimpl.cpp.

◆ elseExp()

QgsExpressionNode * QgsExpressionNodeCondition::elseExp ( ) const

inline

The ELSE expression used for the condition.

Returns: The ELSE expression used for the condition.

Definition at line 640 of file qgsexpressionnodeimpl.h.

◆ evalNode()

QVariant QgsExpressionNodeCondition::evalNode	(	QgsExpression *	parent,
		const QgsExpressionContext *	context
	)

overridevirtual

Abstract virtual eval method Errors are reported to the parent.

Implements QgsExpressionNode.

Definition at line 1729 of file qgsexpressionnodeimpl.cpp.

◆ isStatic()

bool QgsExpressionNodeCondition::isStatic	(	QgsExpression *	parent,
		const QgsExpressionContext *	context
	)		const

overridevirtual

Returns true if this node can be evaluated for a static value.

This is used during the prepare() step and in case it returns true, the value of this node will already be evaluated and the result cached (and therefore not re-evaluated in subsequent calls to eval()). In case this returns true, prepareNode() will never be called.

Implements QgsExpressionNode.

Definition at line 1912 of file qgsexpressionnodeimpl.cpp.

◆ needsGeometry()

bool QgsExpressionNodeCondition::needsGeometry ( ) const

overridevirtual

Abstract virtual method which returns if the geometry is required to evaluate this expression.

This needs to call needsGeometry() recursively on any child nodes.

Returns: true if a geometry is required to evaluate this expression

Implements QgsExpressionNode.

Definition at line 1888 of file qgsexpressionnodeimpl.cpp.

◆ nodes()

QList< const QgsExpressionNode * > QgsExpressionNodeCondition::nodes ( ) const

overridevirtual

Returns a list of all nodes which are used in this expression.

Note: not available in Python bindings

Since: QGIS 3.2

Implements QgsExpressionNode.

Definition at line 1873 of file qgsexpressionnodeimpl.cpp.

◆ nodeType()

QgsExpressionNode::NodeType QgsExpressionNodeCondition::nodeType ( ) const

overridevirtual

Gets the type of this node.

Returns: The type of this node

Implements QgsExpressionNode.

Definition at line 1724 of file qgsexpressionnodeimpl.cpp.

◆ prepareNode()

bool QgsExpressionNodeCondition::prepareNode	(	QgsExpression *	parent,
		const QgsExpressionContext *	context
	)

overridevirtual

Abstract virtual preparation method Errors are reported to the parent.

Implements QgsExpressionNode.

Definition at line 1755 of file qgsexpressionnodeimpl.cpp.

◆ referencedColumns()

QSet< QString > QgsExpressionNodeCondition::referencedColumns ( ) const

overridevirtual

Abstract virtual method which returns a list of columns required to evaluate this node.

When reimplementing this, you need to return any column that is required to evaluate this node and in addition recursively collect all the columns required to evaluate child nodes.

Warning: If the expression has been prepared via a call to QgsExpression::prepare(), or a call to QgsExpressionNode::prepare() for a node has been made, then some nodes in the expression may have been determined to evaluate to a static pre-calculatable value. In this case the results will omit attribute indices which are used by these pre-calculated nodes, regardless of their actual referenced columns. If you are seeking to use these functions to introspect an expression you must take care to do this with an unprepared expression node.

Returns: A list of columns required to evaluate this expression

Implements QgsExpressionNode.

Definition at line 1828 of file qgsexpressionnodeimpl.cpp.

◆ referencedFunctions()

QSet< QString > QgsExpressionNodeCondition::referencedFunctions ( ) const

overridevirtual

Returns a set of all functions which are used in this expression.

Note: In contrast to the referencedColumns() function this method is not affected by any previous calls to QgsExpressionNode::prepare().

Implements QgsExpressionNode.

Definition at line 1859 of file qgsexpressionnodeimpl.cpp.

◆ referencedVariables()

QSet< QString > QgsExpressionNodeCondition::referencedVariables ( ) const

overridevirtual

Returns a set of all variables which are used in this expression.

Note: In contrast to the referencedColumns() function this method is not affected by any previous calls to QgsExpressionNode::prepare().

Implements QgsExpressionNode.

Definition at line 1845 of file qgsexpressionnodeimpl.cpp.

The documentation for this class was generated from the following files:

/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/expression/qgsexpressionnodeimpl.h
/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/expression/qgsexpressionnodeimpl.cpp

Classes

Public Types

Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ WhenThenList

Constructor & Destructor Documentation

◆ QgsExpressionNodeCondition() [1/2]

◆ QgsExpressionNodeCondition() [2/2]

◆ ~QgsExpressionNodeCondition()

Member Function Documentation

◆ clone()

◆ conditions()

◆ dump()

◆ elseExp()

◆ evalNode()

◆ isStatic()

◆ needsGeometry()

◆ nodes()

◆ nodeType()

◆ prepareNode()

◆ referencedColumns()

◆ referencedFunctions()

◆ referencedVariables()