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Public Member Functions | List of all members
QgsExpression::Function Class Referenceabstract

A abstract base class for defining QgsExpression functions. More...

#include <qgsexpression.h>

Inheritance diagram for QgsExpression::Function:
Inheritance graph
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Public Member Functions

 Function (const QString &fnname, int params, QString group, QString helpText=QString(), bool usesGeometry=false, QStringList referencedColumns=QStringList(), bool lazyEval=false, bool handlesNull=false)
 
virtual ~Function ()
 
virtual QStringList aliases () const
 Returns a list of possible aliases for the function. More...
 
virtual QVariant func (const QVariantList &values, const QgsFeature *f, QgsExpression *parent)=0
 
QString group ()
 The group the function belongs to. More...
 
virtual bool handlesNull () const
 
const QString helptext ()
 The help text for the function. More...
 
bool lazyEval ()
 True if this function should use lazy evaluation. More...
 
QString name ()
 The name of the function. More...
 
bool operator== (const Function &other) const
 
int params ()
 The number of parameters this function takes. More...
 
virtual QStringList referencedColumns () const
 
bool usesgeometry ()
 Does this function use a geometry object. More...
 

Detailed Description

A abstract base class for defining QgsExpression functions.

Definition at line 286 of file qgsexpression.h.

Constructor & Destructor Documentation

QgsExpression::Function::Function ( const QString fnname,
int  params,
QString  group,
QString  helpText = QString(),
bool  usesGeometry = false,
QStringList  referencedColumns = QStringList(),
bool  lazyEval = false,
bool  handlesNull = false 
)
inline

Definition at line 289 of file qgsexpression.h.

virtual QgsExpression::Function::~Function ( )
inlinevirtual

Definition at line 307 of file qgsexpression.h.

Member Function Documentation

virtual QStringList QgsExpression::Function::aliases ( ) const
inlinevirtual

Returns a list of possible aliases for the function.

These include other permissible names for the function, eg deprecated names.

Returns
list of known aliases
Note
added in QGIS 2.9

Reimplemented in QgsExpression::StaticFunction.

Definition at line 321 of file qgsexpression.h.

virtual QVariant QgsExpression::Function::func ( const QVariantList &  values,
const QgsFeature f,
QgsExpression parent 
)
pure virtual
QString QgsExpression::Function::group ( )
inline

The group the function belongs to.

Definition at line 331 of file qgsexpression.h.

virtual bool QgsExpression::Function::handlesNull ( ) const
inlinevirtual

Definition at line 345 of file qgsexpression.h.

const QString QgsExpression::Function::helptext ( )
inline

The help text for the function.

Definition at line 333 of file qgsexpression.h.

bool QgsExpression::Function::lazyEval ( )
inline

True if this function should use lazy evaluation.

Lazy evaluation functions take QgsExpression::Node objects rather than the node results when called. You can use node->eval(parent, feature) to evaluate the node and return the result Functions are non lazy default and will be given the node return value when called

Definition at line 326 of file qgsexpression.h.

QString QgsExpression::Function::name ( )
inline

The name of the function.

Definition at line 310 of file qgsexpression.h.

bool QgsExpression::Function::operator== ( const Function other) const
inline

Definition at line 337 of file qgsexpression.h.

int QgsExpression::Function::params ( )
inline

The number of parameters this function takes.

Definition at line 312 of file qgsexpression.h.

virtual QStringList QgsExpression::Function::referencedColumns ( ) const
inlinevirtual

Definition at line 328 of file qgsexpression.h.

bool QgsExpression::Function::usesgeometry ( )
inline

Does this function use a geometry object.

Definition at line 314 of file qgsexpression.h.


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