Class storing parameters of a scale expression, which is a subclass of QgsExpression for expressions which return a size or width. More...

#include <qgsscaleexpression.h>

Inheritance diagram for QgsScaleExpression:

[legend]

Public Types
enum	Type { Linear, Area, Flannery, Exponential, Unknown }

Public Types inherited from QgsExpression
enum	BinaryOperator { boOr, boAnd, boEQ, boNE, boLE, boGE, boLT, boGT, boRegexp, boLike, boNotLike, boILike, boNotILike, boIs, boIsNot, boPlus, boMinus, boMul, boDiv, boIntDiv, boMod, boPow, boConcat }
	list of binary operators More...

typedef QVariant(*	FcnEval) (const QVariantList &values, const QgsFeature f, QgsExpression parent)

typedef QVariant(*	FcnEvalContext) (const QVariantList &values, const QgsExpressionContext context, QgsExpression parent)
	Function definition for evaluation against an expression context, using a list of values as parameters to the function. More...

typedef QgsInterval	Interval

enum	NodeType { ntUnaryOperator, ntBinaryOperator, ntInOperator, ntFunction, ntLiteral, ntColumnRef, ntCondition }

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

enum	SpatialOperator { soBbox, soIntersects, soContains, soCrosses, soEquals, soDisjoint, soOverlaps, soTouches, soWithin }

enum	UnaryOperator { uoNot, uoMinus }
	list of unary operators More...

typedef QList< WhenThen * >	WhenThenList

Public Member Functions
	QgsScaleExpression (const QString &expression)
	Constructor for QgsScaleExpression which parses an expression string to determine whether it's a scale expression. More...

	QgsScaleExpression (Type type, const QString &baseExpression, double minValue, double maxValue, double minSize, double maxSize, double nullSize=0, double exponent=1)
	Constructor for QgsScaleExpression which creates an expression from specified parameters. More...

QString	baseExpression () const
	Returns the base expression string (or field reference) used for calculating the values to be mapped to a size. More...

double	exponent () const
	Returns the exponent of the exponential expression. More...

double	maxSize () const
	Returns the maximum size calculated by the expression. More...

double	maxValue () const
	Returns the maximum value expected by the expression. More...

double	minSize () const
	Returns the minimum size calculated by the expression. More...

double	minValue () const
	Returns the minimum value expected by the expression. More...

double	nullSize () const
	Returns the size value when expression evaluates to NULL. More...

	operator bool () const

double	size (double value) const
	Calculates the size corresponding to a specific value. More...

Type	type () const
	Returns the scale expression's type (method used to calculate the size from a value). More...

Public Member Functions inherited from QgsExpression
	QgsExpression (const QString &expr)
	Creates a new expression based on the provided string. More...

	QgsExpression (const QgsExpression &other)
	Create a copy of this expression. More...

	QgsExpression ()
	Create an empty expression. More...

	~QgsExpression ()

void	acceptVisitor (Visitor &v) const
	Entry function for the visitor pattern. More...

QgsUnitTypes::AreaUnit	areaUnits () const
	Returns the desired areal units for calculations involving geomCalculator(), eg "$area". More...

Q_DECL_DEPRECATED int	currentRowNumber ()
	Return the number used for $rownum special column. More...

QGis::UnitType	distanceUnits () const
	Returns the desired distance units for calculations involving geomCalculator(), eg "$length" and "$perimeter". More...

QString	dump () const
	Return an expression string, constructed from the internal abstract syntax tree. More...

QString	evalErrorString () const
	Returns evaluation error. More...

Q_DECL_DEPRECATED QVariant	evaluate (const QgsFeature *f)
	Evaluate the feature and return the result. More...

Q_DECL_DEPRECATED QVariant	evaluate (const QgsFeature &f)
	Evaluate the feature and return the result. More...

Q_DECL_DEPRECATED QVariant	evaluate (const QgsFeature *f, const QgsFields &fields)
	Evaluate the feature and return the result. More...

Q_DECL_DEPRECATED QVariant	evaluate (const QgsFeature &f, const QgsFields &fields)
	Evaluate the feature and return the result. More...

QVariant	evaluate ()
	Evaluate the feature and return the result. More...

QVariant	evaluate (const QgsExpressionContext *context)
	Evaluate the expression against the specified context and return the result. More...

QString	expression () const
	Return the original, unmodified expression string. More...

QgsDistanceArea *	geomCalculator ()
	Return calculator used for distance and area calculations (used by $length, $area and $perimeter functions only) More...

bool	hasEvalError () const
	Returns true if an error occurred when evaluating last input. More...

bool	hasParserError () const
	Returns true if an error occurred when parsing the input expression. More...

bool	isField () const
	Checks whether an expression consists only of a single field reference. More...

bool	isValid () const
	Checks if this expression is valid. More...

bool	needsGeometry () const
	Returns true if the expression uses feature geometry for some computation. More...

QgsExpression &	operator= (const QgsExpression &other)
	Create a copy of this expression. More...

bool	operator== (const QgsExpression &other) const
	Compares two expressions. More...

QString	parserErrorString () const
	Returns parser error. More...

Q_DECL_DEPRECATED bool	prepare (const QgsFields &fields)
	Get the expression ready for evaluation - find out column indexes. More...

bool	prepare (const QgsExpressionContext *context)
	Get the expression ready for evaluation - find out column indexes. More...

QStringList	referencedColumns () const
	Get list of columns referenced by the expression. More...

const Node *	rootNode () const
	Returns root node of the expression. Root node is null is parsing has failed. More...

double	scale ()

void	setAreaUnits (QgsUnitTypes::AreaUnit unit)
	Sets the desired areal units for calculations involving geomCalculator(), eg "$area". More...

Q_DECL_DEPRECATED void	setCurrentRowNumber (int rowNumber)
	Set the number for $rownum special column. More...

void	setDistanceUnits (QGis::UnitType unit)
	Sets the desired distance units for calculations involving geomCalculator(), eg "$length" and "$perimeter". More...

void	setEvalErrorString (const QString &str)
	Set evaluation error (used internally by evaluation functions) More...

void	setExpression (const QString &expression)
	Set the expression string, will reset the whole internal structure. More...

void	setGeomCalculator (const QgsDistanceArea &calc)
	Sets the geometry calculator used for distance and area calculations in expressions. More...

void	setScale (double scale)

Additional Inherited Members
Static Public Member Functions inherited from QgsExpression
static const QStringList &	BuiltinFunctions ()

static void	cleanRegisteredFunctions ()
	Deletes all registered functions whose ownership have been transferred to the expression engine. More...

static QString	createFieldEqualityExpression (const QString &fieldName, const QVariant &value)
	Create an expression allowing to evaluate if a field is equal to a value. More...

static double	evaluateToDouble (const QString &text, const double fallbackValue)
	Attempts to evaluate a text string as an expression to a resultant double value. More...

static QString	formatPreviewString (const QVariant &value)
	Formats an expression result for friendly display to the user. More...

static int	functionCount ()
	Returns the number of functions defined in the parser. More...

static int	functionIndex (const QString &name)
	return index of the function in Functions array More...

static const QList< Function * > &	Functions ()

static QString	group (const QString &group)
	Returns the translated name for a function group. More...

static bool	hasSpecialColumn (const QString &name)
	Check whether a special column exists. More...

static QString	helptext (QString name)
	Returns the help text for a specified function. More...

static bool	isFunctionName (const QString &name)
	tells whether the identifier is a name of existing function More...

static Q_DECL_DEPRECATED bool	isValid (const QString &text, const QgsFields &fields, QString &errorMessage)

static bool	isValid (const QString &text, const QgsExpressionContext *context, QString &errorMessage)
	Tests whether a string is a valid expression. More...

static QString	quotedColumnRef (QString name)
	Returns a quoted column reference (in double quotes) More...

static QString	quotedString (QString text)
	Returns a quoted version of a string (in single quotes) More...

static QString	quotedValue (const QVariant &value)
	Returns a string representation of a literal value, including appropriate quotations where required. More...

static QString	quotedValue (const QVariant &value, QVariant::Type type)
	Returns a string representation of a literal value, including appropriate quotations where required. More...

static bool	registerFunction (Function *function, bool transferOwnership=false)
	Registers a function to the expression engine. More...

static Q_DECL_DEPRECATED QString	replaceExpressionText (const QString &action, const QgsFeature feat, QgsVectorLayer layer, const QMap< QString, QVariant > substitutionMap=nullptr, const QgsDistanceArea distanceArea=nullptr)
	This function currently replaces each expression between [% and %] in the string with the result of its evaluation on the feature passed as argument. More...

static QString	replaceExpressionText (const QString &action, const QgsExpressionContext context, const QMap< QString, QVariant > substitutionMap=nullptr, const QgsDistanceArea *distanceArea=nullptr)
	This function replaces each expression between [% and %] in the string with the result of its evaluation with the specified context. More...

static Q_DECL_DEPRECATED void	setSpecialColumn (const QString &name, const QVariant &value)
	Assign a special column. More...

static Q_DECL_DEPRECATED QVariant	specialColumn (const QString &name)
	Return the value of the given special column or a null QVariant if undefined. More...

static QList< Function * >	specialColumns ()
	Returns a list of special Column definitions. More...

static bool	unregisterFunction (const QString &name)
	Unregisters a function from the expression engine. More...

static Q_DECL_DEPRECATED void	unsetSpecialColumn (const QString &name)
	Unset a special column. More...

static QString	variableHelpText (const QString &variableName, bool showValue=true, const QVariant &value=QVariant())
	Returns the help text for a specified variable. More...

Static Public Attributes inherited from QgsExpression
static const char *	BinaryOperatorText []

static QStringList	gmBuiltinFunctions

static QList< Function * >	gmFunctions

static QList< Function * >	gmOwnedFunctions
	List of functions owned by the expression engine. More...

static const char *	UnaryOperatorText []

Protected Member Functions inherited from QgsExpression
void	detach ()
	Helper for implicit sharing. More...

void	initGeomCalculator ()

Static Protected Member Functions inherited from QgsExpression
static void	initFunctionHelp ()

static void	initVariableHelp ()

Protected Attributes inherited from QgsExpression
QgsExpressionPrivate *	d

Static Protected Attributes inherited from QgsExpression
static QHash< QString, Help >	gFunctionHelpTexts

static QHash< QString, QString >	gGroups

static QMap< QString, QString >	gmSpecialColumnGroups

static QMap< QString, QVariant >	gmSpecialColumns

static QHash< QString, QString >	gVariableHelpTexts

Detailed Description

Class storing parameters of a scale expression, which is a subclass of QgsExpression for expressions which return a size or width.

Note: Added in version 2.9

Definition at line 28 of file qgsscaleexpression.h.

Member Enumeration Documentation

◆ Type

enum QgsScaleExpression::Type

Enumerator
Linear
Area
Flannery
Exponential
Unknown

Definition at line 32 of file qgsscaleexpression.h.

Constructor & Destructor Documentation

◆ QgsScaleExpression() [1/2]

QgsScaleExpression::QgsScaleExpression ( const QString & expression )

Constructor for QgsScaleExpression which parses an expression string to determine whether it's a scale expression.

Parameters

expression expression string

Definition at line 21 of file qgsscaleexpression.cpp.

◆ QgsScaleExpression() [2/2]

QgsScaleExpression::QgsScaleExpression	(	Type	type,
		const QString &	baseExpression,
		double	minValue,
		double	maxValue,
		double	minSize,
		double	maxSize,
		double	nullSize = `0`,
		double	exponent = `1`
	)

Constructor for QgsScaleExpression which creates an expression from specified parameters.

Parameters

type	scale method
baseExpression	expression (or field) used for value
minValue	minimum value, corresponds to specified minimum size
maxValue	maximum value, corresponds to specified maximum size
minSize	minimum size
maxSize	maximum size
nullSize	size in case expression evaluates to NULL
exponent	to use in case of Exponential type

Definition at line 34 of file qgsscaleexpression.cpp.

Member Function Documentation

◆ baseExpression()

QString QgsScaleExpression::baseExpression ( ) const

inline

Returns the base expression string (or field reference) used for calculating the values to be mapped to a size.

Definition at line 103 of file qgsscaleexpression.h.

◆ exponent()

double QgsScaleExpression::exponent ( ) const

inline

Returns the exponent of the exponential expression.

See also: exponent

Definition at line 98 of file qgsscaleexpression.h.

◆ maxSize()

double QgsScaleExpression::maxSize ( ) const

inline

Returns the maximum size calculated by the expression.

See also: minSize

Definition at line 76 of file qgsscaleexpression.h.

◆ maxValue()

double QgsScaleExpression::maxValue ( ) const

inline

Returns the maximum value expected by the expression.

The maximum value corresponds to the expression's maximum size.

See also: minValue

Definition at line 88 of file qgsscaleexpression.h.

◆ minSize()

double QgsScaleExpression::minSize ( ) const

inline

Returns the minimum size calculated by the expression.

See also: maxSize

Definition at line 71 of file qgsscaleexpression.h.

◆ minValue()

double QgsScaleExpression::minValue ( ) const

inline

Returns the minimum value expected by the expression.

The minimum value corresponds to the expression's minimum size.

See also: maxValue

Definition at line 82 of file qgsscaleexpression.h.

◆ nullSize()

double QgsScaleExpression::nullSize ( ) const

inline

Returns the size value when expression evaluates to NULL.

See also: nullSize

Definition at line 93 of file qgsscaleexpression.h.

◆ operator bool()

QgsScaleExpression::operator bool ( ) const

inline

Definition at line 60 of file qgsscaleexpression.h.

◆ size()

double QgsScaleExpression::size ( double value ) const

Calculates the size corresponding to a specific value.

Parameters

value

Returns: calculated size using expression's parameters and type

Definition at line 155 of file qgsscaleexpression.cpp.

◆ type()

Type QgsScaleExpression::type ( ) const

inline

Returns the scale expression's type (method used to calculate the size from a value).

Definition at line 108 of file qgsscaleexpression.h.

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

/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsscaleexpression.h
/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsscaleexpression.cpp

Public Types

Public Member Functions

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ Type

Constructor & Destructor Documentation

◆ QgsScaleExpression() [1/2]

◆ QgsScaleExpression() [2/2]

Member Function Documentation

◆ baseExpression()

◆ exponent()

◆ maxSize()

◆ maxValue()

◆ minSize()

◆ minValue()

◆ nullSize()

◆ operator bool()

◆ size()

◆ type()