Single scope for storing variables and functions for use within a QgsExpressionContext. More...

#include <qgsexpressioncontext.h>

Classes
struct	StaticVariable
	Single variable definition for use within a QgsExpressionContextScope. More...

Public Member Functions
	QgsExpressionContextScope (const QgsExpressionContextScope &other)

	QgsExpressionContextScope (const QString &name=QString())
	Constructor for QgsExpressionContextScope.

	~QgsExpressionContextScope ()

void	addFunction (const QString &name, QgsScopedExpressionFunction *function)
	Adds a function to the scope.

void	addHiddenVariable (const QString &hiddenVariable)
	Adds the passed variable to a list of hidden variables that won't be visible in the expression builder dialog and widget.

void	addLayerStore (QgsMapLayerStore *store)
	Adds a layer store to the scope.

void	addVariable (const QgsExpressionContextScope::StaticVariable &variable)
	Adds a variable into the context scope.

QString	description (const QString &name) const
	Returns the translated description for the variable with the specified name (if set).

QgsFeature	feature () const
	Sets the feature associated with the scope.

QStringList	filteredVariableNames () const
	Returns a filtered and sorted list of variable names contained within the scope.

QgsExpressionFunction *	function (const QString &name) const
	Retrieves a function from the scope.

QStringList	functionNames () const
	Retrieves a list of names of functions contained in the scope.

QgsGeometry	geometry () const
	Sets the geometry associated with the scope.

bool	hasFeature () const
	Returns `true` if the scope has a feature associated with it.

bool	hasFunction (const QString &name) const
	Tests whether a function with the specified name exists in the scope.

bool	hasGeometry () const
	Returns `true` if the scope has a geometry associated with it.

bool	hasVariable (const QString &name) const
	Tests whether a variable with the specified name exists in the scope.

QStringList	hiddenVariables () const
	Returns the list of variables hidden within the scope.

bool	isReadOnly (const QString &name) const
	Tests whether the specified variable is read only and should not be editable by users.

bool	isStatic (const QString &name) const
	Tests whether the variable with the specified name is static and can be cached.

QList< QgsMapLayerStore * >	layerStores () const
	Returns the list of layer stores associated with the scope.

QString	name () const
	Returns the friendly display name of the context scope.

QgsExpressionContextScope &	operator= (const QgsExpressionContextScope &other)

void	readXml (const QDomElement &element, const QgsReadWriteContext &context)
	Reads scope variables from an XML element.

void	removeFeature ()
	Removes any feature associated with the scope.

void	removeGeometry ()
	Removes any geometry associated with the scope.

void	removeHiddenVariable (const QString &hiddenVariable)
	Removes the passed variable from a list of hidden variables.

bool	removeVariable (const QString &name)
	Removes a variable from the context scope, if found.

void	setFeature (const QgsFeature &feature)
	Convenience function for setting a feature for the scope.

void	setFields (const QgsFields &fields)
	Convenience function for setting a fields for the scope.

void	setGeometry (const QgsGeometry &geometry)
	Convenience function for setting a geometry for the scope.

void	setHiddenVariables (const QStringList &hiddenVariables)
	Sets the list of variables intended to be hidden in the expression builder dialog and widget.

void	setVariable (const QString &name, const QVariant &value, bool isStatic=false)
	Convenience method for setting a variable in the context scope by name name and value.

QVariant	variable (const QString &name) const
	Retrieves a variable's value from the scope.

int	variableCount () const
	Returns the count of variables contained within the scope.

QStringList	variableNames () const
	Returns a list of variable names contained within the scope.

bool	writeXml (QDomElement &element, QDomDocument &document, const QgsReadWriteContext &context) const
	Writes scope variables to an XML element.

Detailed Description

Single scope for storing variables and functions for use within a QgsExpressionContext.

Examples include a project's scope, which could contain information about the current project such as the project file's location. QgsExpressionContextScope can encapsulate both variables (static values) and functions(which are calculated only when an expression is evaluated).

See QgsExpressionContextUtils for helper methods for working with QgsExpressionContextScope objects.

Definition at line 114 of file qgsexpressioncontext.h.

Constructor & Destructor Documentation

◆ QgsExpressionContextScope() [1/2]

QgsExpressionContextScope::QgsExpressionContextScope ( const QString & name = QString() )

Constructor for QgsExpressionContextScope.

Parameters

name	friendly display name for the context scope

Definition at line 38 of file qgsexpressioncontext.cpp.

◆ QgsExpressionContextScope() [2/2]

QgsExpressionContextScope::QgsExpressionContextScope ( const QgsExpressionContextScope & other )

Definition at line 44 of file qgsexpressioncontext.cpp.

◆ ~QgsExpressionContextScope()

QgsExpressionContextScope::~QgsExpressionContextScope ( )

Definition at line 83 of file qgsexpressioncontext.cpp.

Member Function Documentation

◆ addFunction()

void QgsExpressionContextScope::addFunction	(	const QString &	name,
		QgsScopedExpressionFunction *	function
	)

Adds a function to the scope.

Parameters

name	function name
function	function to insert. Ownership is transferred to the scope.

See also: addVariable()

Definition at line 249 of file qgsexpressioncontext.cpp.

◆ addHiddenVariable()

void QgsExpressionContextScope::addHiddenVariable ( const QString & hiddenVariable )

Adds the passed variable to a list of hidden variables that won't be visible in the expression builder dialog and widget.

See also: hiddenVariables(); setHiddenVariables(); removeHiddenVariable()

Since: QGIS 3.28

Definition at line 150 of file qgsexpressioncontext.cpp.

◆ addLayerStore()

void QgsExpressionContextScope::addLayerStore ( QgsMapLayerStore * store )

Adds a layer store to the scope.

Ownership of the store is not transferred to the scope, it is the caller's responsibility to ensure that the store remains alive for the duration of the expression context.

See also: layerStores()

Since: QGIS 3.30

Definition at line 162 of file qgsexpressioncontext.cpp.

◆ addVariable()

void QgsExpressionContextScope::addVariable ( const QgsExpressionContextScope::StaticVariable & variable )

Adds a variable into the context scope.

If a variable with the same name is already set then its value is overwritten, otherwise a new variable is added to the scope.

Parameters

variable definition of variable to insert

See also: setVariable(); addFunction()

Definition at line 102 of file qgsexpressioncontext.cpp.

◆ description()

QString QgsExpressionContextScope::description ( const QString & name ) const

Returns the translated description for the variable with the specified name (if set).

Definition at line 229 of file qgsexpressioncontext.cpp.

◆ feature()

QgsFeature QgsExpressionContextScope::feature ( ) const

inline

Sets the feature associated with the scope.

See also: setFeature(); hasFeature()

Definition at line 304 of file qgsexpressioncontext.h.

◆ filteredVariableNames()

QStringList QgsExpressionContextScope::filteredVariableNames ( ) const

Returns a filtered and sorted list of variable names contained within the scope.

Hidden variable names will be excluded, and the list will be sorted so that read only variables are listed first.

See also: variableNames()

Definition at line 201 of file qgsexpressioncontext.cpp.

◆ function()

QgsExpressionFunction * QgsExpressionContextScope::function ( const QString & name ) const

Retrieves a function from the scope.

Parameters

name	function name

Returns: function, or nullptr if matching function could not be found

See also: hasFunction(); functionNames(); variable()

Definition at line 239 of file qgsexpressioncontext.cpp.

◆ functionNames()

QStringList QgsExpressionContextScope::functionNames ( ) const

Retrieves a list of names of functions contained in the scope.

See also: function(); variableNames()

Definition at line 244 of file qgsexpressioncontext.cpp.

◆ geometry()

QgsGeometry QgsExpressionContextScope::geometry ( ) const

inline

Sets the geometry associated with the scope.

See also: setGeometry(); hasGeometry()

Since: QGIS 3.24

Definition at line 335 of file qgsexpressioncontext.h.

◆ hasFeature()

bool QgsExpressionContextScope::hasFeature ( ) const

inline

Returns true if the scope has a feature associated with it.

See also: feature()

Definition at line 297 of file qgsexpressioncontext.h.

◆ hasFunction()

bool QgsExpressionContextScope::hasFunction ( const QString & name ) const

Tests whether a function with the specified name exists in the scope.

Parameters

name	function name

Returns: true if matching function was found in the scope

See also: function(); hasFunction()

Definition at line 234 of file qgsexpressioncontext.cpp.

◆ hasGeometry()

bool QgsExpressionContextScope::hasGeometry ( ) const

inline

Returns true if the scope has a geometry associated with it.

See also: geometry()

Since: QGIS 3.24

Definition at line 327 of file qgsexpressioncontext.h.

◆ hasVariable()

bool QgsExpressionContextScope::hasVariable ( const QString & name ) const

Tests whether a variable with the specified name exists in the scope.

Parameters

name	variable name

Returns: true if matching variable was found in the scope

See also: variable(); hasFunction()

Definition at line 116 of file qgsexpressioncontext.cpp.

◆ hiddenVariables()

QStringList QgsExpressionContextScope::hiddenVariables ( ) const

Returns the list of variables hidden within the scope.

See also: setHiddenVariables(); addHiddenVariable(); removeHiddenVariable()

Since: QGIS 3.28

Definition at line 140 of file qgsexpressioncontext.cpp.

◆ isReadOnly()

bool QgsExpressionContextScope::isReadOnly ( const QString & name ) const

Tests whether the specified variable is read only and should not be editable by users.

Parameters

name	variable name

Returns: true if variable is read only

Definition at line 219 of file qgsexpressioncontext.cpp.

◆ isStatic()

bool QgsExpressionContextScope::isStatic ( const QString & name ) const

Tests whether the variable with the specified name is static and can be cached.

Definition at line 224 of file qgsexpressioncontext.cpp.

◆ layerStores()

QList< QgsMapLayerStore * > QgsExpressionContextScope::layerStores ( ) const

Returns the list of layer stores associated with the scope.

See also: addLayerStore()

Since: QGIS 3.30

Definition at line 167 of file qgsexpressioncontext.cpp.

◆ name()

QString QgsExpressionContextScope::name ( ) const

inline

Returns the friendly display name of the context scope.

Definition at line 171 of file qgsexpressioncontext.h.

◆ operator=()

QgsExpressionContextScope & QgsExpressionContextScope::operator= ( const QgsExpressionContextScope & other )

Definition at line 61 of file qgsexpressioncontext.cpp.

◆ readXml()

void QgsExpressionContextScope::readXml	(	const QDomElement &	element,
		const QgsReadWriteContext &	context
	)

Reads scope variables from an XML element.

See also: writeXml()

Since: QGIS 3.6

Definition at line 260 of file qgsexpressioncontext.cpp.

◆ removeFeature()

void QgsExpressionContextScope::removeFeature ( )

inline

Removes any feature associated with the scope.

See also: setFeature(); hasFeature()

Definition at line 320 of file qgsexpressioncontext.h.

◆ removeGeometry()

void QgsExpressionContextScope::removeGeometry ( )

inline

Removes any geometry associated with the scope.

See also: setGeometry(); hasGeometry()

Since: QGIS 3.24

Definition at line 353 of file qgsexpressioncontext.h.

◆ removeHiddenVariable()

void QgsExpressionContextScope::removeHiddenVariable ( const QString & hiddenVariable )

Removes the passed variable from a list of hidden variables.

See also: hiddenVariables(); setHiddenVariables(); addHiddenVariable()

Since: QGIS 3.28

Definition at line 156 of file qgsexpressioncontext.cpp.

◆ removeVariable()

bool QgsExpressionContextScope::removeVariable ( const QString & name )

Removes a variable from the context scope, if found.

Parameters

name	name of variable to remove

Returns: true if variable was removed from the scope, false if matching variable was not found within the scope

Definition at line 107 of file qgsexpressioncontext.cpp.

◆ setFeature()

void QgsExpressionContextScope::setFeature ( const QgsFeature & feature )

inline

Convenience function for setting a feature for the scope.

Any existing feature set by the scope will be overwritten.

Parameters

feature feature for scope

See also: removeFeature(); feature()

Definition at line 313 of file qgsexpressioncontext.h.

◆ setFields()

void QgsExpressionContextScope::setFields ( const QgsFields & fields )

Convenience function for setting a fields for the scope.

Any existing fields set by the scope will be overwritten.

Parameters

fields fields for scope

Definition at line 255 of file qgsexpressioncontext.cpp.

◆ setGeometry()

void QgsExpressionContextScope::setGeometry ( const QgsGeometry & geometry )

inline

Convenience function for setting a geometry for the scope.

Any existing geometry set by the scope will be overwritten.

See also: removeGeometry(); geometry()

Since: QGIS 3.24

Definition at line 345 of file qgsexpressioncontext.h.

◆ setHiddenVariables()

void QgsExpressionContextScope::setHiddenVariables ( const QStringList & hiddenVariables )

Sets the list of variables intended to be hidden in the expression builder dialog and widget.

See also: hiddenVariables(); addHiddenVariable(); removeHiddenVariable()

Since: QGIS 3.28

Definition at line 145 of file qgsexpressioncontext.cpp.

◆ setVariable()

void QgsExpressionContextScope::setVariable	(	const QString &	name,
		const QVariant &	value,
		bool	isStatic = `false`
	)

Convenience method for setting a variable in the context scope by name name and value.

If a variable with the same name is already set then its value is overwritten, otherwise a new variable is added to the scope. If the isStatic parameter is set to true, this variable can be cached during the execution of QgsExpression::prepare().

See also: addVariable()

Definition at line 88 of file qgsexpressioncontext.cpp.

◆ variable()

QVariant QgsExpressionContextScope::variable ( const QString & name ) const

Retrieves a variable's value from the scope.

Parameters

name	variable name

Returns: variable value, or invalid QVariant if matching variable could not be found

See also: hasVariable(); function()

Definition at line 121 of file qgsexpressioncontext.cpp.

◆ variableCount()

int QgsExpressionContextScope::variableCount ( ) const

inline

Returns the count of variables contained within the scope.

Definition at line 257 of file qgsexpressioncontext.h.

◆ variableNames()

QStringList QgsExpressionContextScope::variableNames ( ) const

Returns a list of variable names contained within the scope.

See also: functionNames(); filteredVariableNames()

Definition at line 126 of file qgsexpressioncontext.cpp.

◆ writeXml()

bool QgsExpressionContextScope::writeXml	(	QDomElement &	element,
		QDomDocument &	document,
		const QgsReadWriteContext &	context
	)		const

Writes scope variables to an XML element.

See also: readXml()

Since: QGIS 3.6

Definition at line 278 of file qgsexpressioncontext.cpp.

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

/build/qgis-3.41.0+git20241214+cea29feecf2+99sid/src/core/qgsexpressioncontext.h
/build/qgis-3.41.0+git20241214+cea29feecf2+99sid/src/core/qgsexpressioncontext.cpp

Classes

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ QgsExpressionContextScope() [1/2]

◆ QgsExpressionContextScope() [2/2]

◆ ~QgsExpressionContextScope()

Member Function Documentation

◆ addFunction()

◆ addHiddenVariable()

◆ addLayerStore()

◆ addVariable()

◆ description()

◆ feature()

◆ filteredVariableNames()

◆ function()

◆ functionNames()

◆ geometry()

◆ hasFeature()

◆ hasFunction()

◆ hasGeometry()

◆ hasVariable()

◆ hiddenVariables()

◆ isReadOnly()

◆ isStatic()

◆ layerStores()

◆ name()

◆ operator=()

◆ readXml()

◆ removeFeature()

◆ removeGeometry()

◆ removeHiddenVariable()

◆ removeVariable()

◆ setFeature()

◆ setFields()

◆ setGeometry()

◆ setHiddenVariables()

◆ setVariable()

◆ variable()

◆ variableCount()

◆ variableNames()

◆ writeXml()