qgsdatadefinedutils.h File Reference

#include <algorithm>
#include <array>
#include <optional>
#include "qgis_core.h"

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Classes
class	QgsDataDefinedStringDecoder< V, N >
	A template based class for efficiently decoding a string value to a corresponding enum value. More...

Macros
#define	SIP_NO_FILE

Functions
template<typename V, size_t N>
constexpr QgsDataDefinedStringDecoder< V, N >	makeDataDefinedStringDecoder (const DataDefinedDecoderEntry< V >(&values)[N])
	Creates a QgsDataDefinedStringDecoder from a hardcoded lookup table.

Macro Definition Documentation

SIP_NO_FILE

#define SIP_NO_FILE

Definition at line 25 of file qgsdatadefinedutils.h.

Function Documentation

makeDataDefinedStringDecoder()

template<typename V, size_t N>

QgsDataDefinedStringDecoder< V, N > makeDataDefinedStringDecoder ( const DataDefinedDecoderEntry< V >(&) values[N] )

constexpr

Creates a QgsDataDefinedStringDecoder from a hardcoded lookup table.

String keys must:

• be non-empty
• start with a letter character (a-z)
• be completely lower-case
• be unique
• not contain spaces, hyphens or underscores

Usage:

// create a decoder once as a static object
static constexpr auto sPointPositionMap = makeDataDefinedStringDecoder<Qgis::LabelPredefinedPointPosition>( {
{ u"topleft", Qgis::LabelPredefinedPointPosition::TopLeft },
{ u"topright", Qgis::LabelPredefinedPointPosition::TopRight }
} );
 
// use the static object to lookup candidate string values
if ( auto evaluatedPosition = sPointPositionMap.lookup( candidate ) )
{
  // string was successfully matched, use the matched enum value
  Qgis::LabelPredefinedPointPosition position = *evaluatedPosition;
}
else
{
  // string did not match any entry in the lookup table...
}

Since

QGIS 4.4

Definition at line 256 of file qgsdatadefinedutils.h.