Handles the with_variable(name, value, node) expression function. More...

#include <qgsexpressionfunction.h>

Inheritance diagram for QgsWithVariableExpressionFunction:

Public Member Functions
	QgsWithVariableExpressionFunction ()

QVariant	func (const QVariantList &values, const QgsExpressionContext context, QgsExpression parent, const QgsExpressionNodeFunction *node) override
	Returns result of evaluating the function.

bool	isStatic (const QgsExpressionNodeFunction node, QgsExpression parent, const QgsExpressionContext *context) const override
	Will be called during prepare to determine if the function is static.

bool	prepare (const QgsExpressionNodeFunction node, QgsExpression parent, const QgsExpressionContext *context) const override
	This will be called during the prepare step() of an expression if it is not static.

QVariant	run (QgsExpressionNode::NodeList args, const QgsExpressionContext context, QgsExpression parent, const QgsExpressionNodeFunction node) override
	Evaluates the function, first evaluating all required arguments before passing them to the function's func() method.

Public Member Functions inherited from QgsExpressionFunction
	QgsExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList &params, const QString &group, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false)
	Constructor for function which uses named parameter list.

	QgsExpressionFunction (const QString &fnname, const QgsExpressionFunction::ParameterList &params, const QStringList &groups, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false)
	Constructor for function which uses named parameter list and group list.

	QgsExpressionFunction (const QString &fnname, int params, const QString &group, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false)
	Constructor for function which uses unnamed parameters.

	QgsExpressionFunction (const QString &fnname, int params, const QStringList &groups, const QString &helpText=QString(), bool lazyEval=false, bool handlesNull=false, bool isContextual=false)
	Constructor for function which uses unnamed parameters and group list.

virtual	~QgsExpressionFunction ()=default

virtual QStringList	aliases () const
	Returns a list of possible aliases for the function.

QString	group () const
	Returns the first group which the function belongs to.

QStringList	groups () const
	Returns a list of the groups the function belongs to.

virtual bool	handlesNull () const
	Returns `true` if the function handles NULL values in arguments by itself, and the default NULL value handling should be skipped.

const QString	helpText () const
	The help text for the function.

bool	isContextual () const
	Returns whether the function is only available if provided by a QgsExpressionContext object.

virtual bool	isDeprecated () const
	Returns `true` if the function is deprecated and should not be presented as a valid option to users in expression builders.

bool	lazyEval () const
	`true` if this function should use lazy evaluation.

int	minParams () const
	The minimum number of parameters this function takes.

QString	name () const
	The name of the function.

bool	operator== (const QgsExpressionFunction &other) const

const QgsExpressionFunction::ParameterList &	parameters () const
	Returns the list of named parameters for the function, if set.

int	params () const
	The number of parameters this function takes.

virtual QSet< QString >	referencedColumns (const QgsExpressionNodeFunction *node) const
	Returns a set of field names which are required for this function.

virtual bool	usesGeometry (const QgsExpressionNodeFunction *node) const
	Does this function use a geometry object.

Additional Inherited Members
Public Types inherited from QgsExpressionFunction
typedef QVariant(*	FcnEval) (const QVariantList &values, const QgsExpressionContext context, QgsExpression parent, const QgsExpressionNodeFunction *node)
	Function definition for evaluation against an expression context, using a list of values as parameters to the function.

typedef QList< QgsExpressionFunction::Parameter >	ParameterList
	List of parameters, used for function definition.

Static Protected Member Functions inherited from QgsExpressionFunction
static bool	allParamsStatic (const QgsExpressionNodeFunction node, QgsExpression parent, const QgsExpressionContext *context)
	This will return `true` if all the params for the provided function node are static within the constraints imposed by the context within the given parent.

Detailed Description

Handles the with_variable(name, value, node) expression function.

It temporarily appends a new scope to the expression context for all nested nodes.

Note: Not available in Python bindings

Definition at line 573 of file qgsexpressionfunction.h.

Constructor & Destructor Documentation

◆ QgsWithVariableExpressionFunction()

QgsWithVariableExpressionFunction::QgsWithVariableExpressionFunction ( )

Definition at line 9530 of file qgsexpressionfunction.cpp.

Member Function Documentation

◆ func()

QVariant QgsWithVariableExpressionFunction::func	(	const QVariantList &	values,
		const QgsExpressionContext *	context,
		QgsExpression *	parent,
		const QgsExpressionNodeFunction *	node
	)

overridevirtual

Returns result of evaluating the function.

Parameters

values	list of values passed to the function
context	context expression is being evaluated against
parent	parent expression
node	expression node

Returns: result of function

Implements QgsExpressionFunction.

Definition at line 9594 of file qgsexpressionfunction.cpp.

◆ isStatic()

bool QgsWithVariableExpressionFunction::isStatic	(	const QgsExpressionNodeFunction *	node,
		QgsExpression *	parent,
		const QgsExpressionContext *	context
	)		const

overridevirtual

Will be called during prepare to determine if the function is static.

A function is static if it will return the same value for every feature with different attributes and/or geometry.

By default this will return true, if all arguments that have been passed to the function are also static.

Reimplemented from QgsExpressionFunction.

Definition at line 9540 of file qgsexpressionfunction.cpp.

◆ prepare()

bool QgsWithVariableExpressionFunction::prepare	(	const QgsExpressionNodeFunction *	node,
		QgsExpression *	parent,
		const QgsExpressionContext *	context
	)		const

overridevirtual

This will be called during the prepare step() of an expression if it is not static.

This can be used by functions to do any preparation steps that might help to speedup the upcoming evaluation.

Reimplemented from QgsExpressionFunction.

Definition at line 9606 of file qgsexpressionfunction.cpp.

◆ run()

QVariant QgsWithVariableExpressionFunction::run	(	QgsExpressionNode::NodeList *	args,
		const QgsExpressionContext *	context,
		QgsExpression *	parent,
		const QgsExpressionNodeFunction *	node
	)

overridevirtual

Evaluates the function, first evaluating all required arguments before passing them to the function's func() method.

Reimplemented from QgsExpressionFunction.

Definition at line 9565 of file qgsexpressionfunction.cpp.

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

/home/fischer/src/qgis-3.38/src/core/expression/qgsexpressionfunction.h
/home/fischer/src/qgis-3.38/src/core/expression/qgsexpressionfunction.cpp

Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsWithVariableExpressionFunction()

Member Function Documentation

◆ func()

◆ isStatic()

◆ prepare()

◆ run()