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

	QgsExpressionContextScope (const QgsExpressionContextScope &other)
	Copy constructor. More...

	~QgsExpressionContextScope ()

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

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

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

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

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

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

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

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

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

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

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

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

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

QgsExpressionContextScope &	operator= (const QgsExpressionContextScope &other)

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

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

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

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

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. More...

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

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

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

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.

Since: QGIS 2.12

Definition at line 129 of file qgsexpressioncontext.h.

Constructor & Destructor Documentation

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

Constructor for QgsExpressionContextScope.

Parameters

name	friendly display name for the context scope

Definition at line 56 of file qgsexpressioncontext.cpp.

QgsExpressionContextScope::QgsExpressionContextScope ( const QgsExpressionContextScope & other )

Copy constructor.

Definition at line 62 of file qgsexpressioncontext.cpp.

QgsExpressionContextScope::~QgsExpressionContextScope ( )

Definition at line 93 of file qgsexpressioncontext.cpp.

Member Function Documentation

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 213 of file qgsexpressioncontext.cpp.

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 113 of file qgsexpressioncontext.cpp.

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

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

Since: QGIS 3.0

Definition at line 193 of file qgsexpressioncontext.cpp.

QgsFeature QgsExpressionContextScope::feature ( ) const

inline

Sets the feature associated with the scope.

See also: setFeature(); hasFeature()

Since: QGIS 3.0

Definition at line 326 of file qgsexpressioncontext.h.

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 166 of file qgsexpressioncontext.cpp.

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

Retrieves a function from the scope.

Parameters

name	function name

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

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

Definition at line 203 of file qgsexpressioncontext.cpp.

QStringList QgsExpressionContextScope::functionNames ( ) const

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

See also: function(); variableNames()

Definition at line 208 of file qgsexpressioncontext.cpp.

bool QgsExpressionContextScope::hasFeature ( ) const

inline

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

See also: feature()

Since: QGIS 3.0

Definition at line 318 of file qgsexpressioncontext.h.

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 198 of file qgsexpressioncontext.cpp.

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 123 of file qgsexpressioncontext.cpp.

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 183 of file qgsexpressioncontext.cpp.

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

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

Since: QGIS 3.0

Definition at line 188 of file qgsexpressioncontext.cpp.

QString QgsExpressionContextScope::name ( ) const

inline

Returns the friendly display name of the context scope.

Definition at line 189 of file qgsexpressioncontext.h.

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

Definition at line 75 of file qgsexpressioncontext.cpp.

void QgsExpressionContextScope::removeFeature ( )

inline

Removes any feature associated with the scope.

See also: setFeature(); hasFeature()

Since: QGIS 3.0

Definition at line 343 of file qgsexpressioncontext.h.

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 118 of file qgsexpressioncontext.cpp.

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 335 of file qgsexpressioncontext.h.

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 219 of file qgsexpressioncontext.cpp.

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().