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/** \ingroup core
* \class QgsDataDefined
* A container class for data source field mapping or expression.
* \note QgsDataDefined objects are implicitly shared.
*/
class QgsDataDefined
{
%TypeHeaderCode
#include <qgsdatadefined.h>
%End
public:
/**
* Construct a new data defined object
*
* @param active Whether the current data defined is active
* @param useexpr Whether to use expression instead of field
* @param expr Expression string
* @param field Field name string
*/
QgsDataDefined( bool active = false,
bool useexpr = false,
const QString& expr = QString(),
const QString& field = QString() );
/**
* Construct a new data defined object, analysing the expression to determine
* if it's a simple field reference or an expression.
* @param expression can be null
*/
explicit QgsDataDefined( const QgsExpression * expression );
/**
* Construct a new data defined object, analysing the string to determine
* if it's a simple field reference or an expression
* @param string field reference or an expression, can be empty
* @note added in QGIS 2.9
*/
explicit QgsDataDefined( const QString& string );
/**
* Copy constructor. Note that copies of data defined objects with expressions
* will not be prepared.
*/
QgsDataDefined( const QgsDataDefined& other );
/** Creates a QgsDataDefined from a decoded QgsStringMap.
* @param map string map encoding of QgsDataDefined
* @param baseName base name for values in the string map
* @returns new QgsDataDefined if string map was successfully interpreted
* @see toMap
* @note added in QGIS 2.9
*/
static QgsDataDefined* fromMap( const QgsStringMap& map, const QString& baseName = QString() );
virtual ~QgsDataDefined();
/** Returns whether the data defined container is set to all the default
* values, ie, disabled, with empty expression and no assigned field
* @returns true if data defined container is set to default values
* @note added in QGIS 2.7
*/
bool hasDefaultValues() const;
bool isActive() const;
void setActive( bool active );
/**
* Returns if the field or the expression part is active.
*
* @return True if it is in expression mode.
*/
bool useExpression() const;
/**
* Controls if the field or the expression part is active.
* For QGIS<=2.10 it is mandatory to call this after {@link setExpressionString}
* or {@link setField}.
*
* @param use True if it should be set to expression mode.
*/
void setUseExpression( bool use );
/**
* Returns the expression string of this QgsDataDefined.
*
* @return An expression
*
* @see field()
* @see expressionOrField()
*/
QString expressionString() const;
/**
* Sets the expression for this QgsDataDefined.
* Will also set useExpression to true.
*
* @param expr The expression to set
*
* @see setField
*/
void setExpressionString( const QString& expr );
/**
* Returns an expression which represents a single field if useExpression returns false, otherwise
* returns the current expression string.
* @return An expression
*
* @note added in 2.12
*/
QString expressionOrField() const;
//! @note not available in python bindings
//QMap<QString, QVariant> expressionParams() const;
//! @note not available in python bindings
//void setExpressionParams( QMap<QString, QVariant> params );
void insertExpressionParam( const QString& key, const QVariant& param );
/** Prepares the expression using a vector layer
* @param layer vector layer
* @returns true if expression was successfully prepared
* @deprecated use QgsExpressionContext variant instead
*/
bool prepareExpression( QgsVectorLayer* layer ) /Deprecated/;
/** Prepares the expression using a fields collection
* @param fields
* @returns true if expression was successfully prepared
* @note added in QGIS 2.9
* @deprecated use QgsExpressionContext variant instead
*/
bool prepareExpression( const QgsFields &fields ) /Deprecated/;
/** Prepares the expression using an expression context.
* @param context expression context
* @returns true if expression was successfully prepared
* @note added in QGIS 2.12
*/
bool prepareExpression( const QgsExpressionContext &context = QgsExpressionContext() );
/** Returns whether the data defined object's expression is prepared
* @returns true if expression is prepared
*/
bool expressionIsPrepared() const;
QgsExpression* expression();
/** Returns the columns referenced by the QgsDataDefined
* @param layer vector layer, used for preparing the expression if required
* @deprecated use QgsExpressionContext variant instead
*/
QStringList referencedColumns( QgsVectorLayer* layer ) /Deprecated/;
/** Returns the columns referenced by the QgsDataDefined
* @param fields vector layer, used for preparing the expression if required
* @note added in QGIS 2.9
* @deprecated use QgsExpressionContext variant instead
*/
QStringList referencedColumns( const QgsFields& fields ) /Deprecated/;
/** Returns the columns referenced by the QgsDataDefined
* @param context expression context, used for preparing the expression if required
* @note added in QGIS 2.12
*/
QStringList referencedColumns( const QgsExpressionContext& context = QgsExpressionContext() );
/**
* Get the field which this QgsDataDefined represents. Be aware that this may return
* a field name which may not be active if useExpression is true.
*
* @return A fieldname
*
* @see expressionOrField()
*/
QString field() const;
/**
* Set the field name which this QgsDataDefined represents.
* Will set useExpression to false.
*
* @param field
*/
void setField( const QString& field );
/** Encodes the QgsDataDefined into a string map.
* @param baseName optional base name for values in the string map. Can be used
* to differentiate multiple QgsDataDefineds encoded in the same string map.
* @see fromMap
*/
QMap< QString, QString > toMap( const QString& baseName = QString() ) const;
/** Returns a DOM element containing the properties of the data defined container.
* @param document DOM document
* @param elementName name for DOM element
* @returns DOM element corresponding to data defined container
* @note added in QGIS 2.7
* @see setFromXmlElement
*/
QDomElement toXmlElement( QDomDocument &document, const QString &elementName ) const;
/** Sets the properties of the data defined container from an XML element. Calling
* this will overwrite all the current properties of the container.
* @param element DOM element
* @returns true if properties were successfully read from element
* @note added in QGIS 2.7
* @see toXmlElement
*/
bool setFromXmlElement( const QDomElement& element );
bool operator==( const QgsDataDefined &other ) const;
bool operator!=( const QgsDataDefined &other ) const;
};
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