QGIS API Documentation 3.34.0-Prizren (ffbdd678812)
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qgsalgorithmorderbyexpression.cpp
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1/***************************************************************************
2 qgsalgorithmorderbyexpression.h
3 ---------------------
4 begin : November 2017
5 copyright : (C) 2017 by Etienne Trimaille
6 email : etienne dot trimaille at gmail dot com
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
18
20#include "qgsfeaturerequest.h"
21
22
24
25QString QgsOrderByExpressionAlgorithm::name() const
26{
27 return QStringLiteral( "orderbyexpression" );
28}
29
30QString QgsOrderByExpressionAlgorithm::displayName() const
31{
32 return QObject::tr( "Order by expression" );
33}
34
35QStringList QgsOrderByExpressionAlgorithm::tags() const
36{
37 return QObject::tr( "orderby,sort,expression,field" ).split( ',' );
38}
39
40QString QgsOrderByExpressionAlgorithm::group() const
41{
42 return QObject::tr( "Vector general" );
43}
44
45QString QgsOrderByExpressionAlgorithm::groupId() const
46{
47 return QStringLiteral( "vectorgeneral" );
48}
49
50void QgsOrderByExpressionAlgorithm::initAlgorithm( const QVariantMap & )
51{
52 addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ), QList< int >() << QgsProcessing::TypeVector ) );
53 addParameter( new QgsProcessingParameterExpression( QStringLiteral( "EXPRESSION" ), QObject::tr( "Expression" ), QVariant(), QStringLiteral( "INPUT" ) ) );
54 addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "ASCENDING" ), QObject::tr( "Sort ascending" ), true ) );
55 addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "NULLS_FIRST" ), QObject::tr( "Sort nulls first" ), false ) );
56
57 addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Ordered" ) ) );
58}
59
60QString QgsOrderByExpressionAlgorithm::shortHelpString() const
61{
62 return QObject::tr( "This algorithm sorts a vector layer according to an expression. Be careful, it might not work as expected with some providers, "
63 "the order might not be kept every time.\n\n"
64 "For help with QGIS expression functions, see the inbuilt help for specific functions "
65 "which is available in the expression builder." );
66}
67
68QgsOrderByExpressionAlgorithm *QgsOrderByExpressionAlgorithm::createInstance() const
69{
70 return new QgsOrderByExpressionAlgorithm();
71}
72
73QVariantMap QgsOrderByExpressionAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
74{
75 std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
76 if ( !source )
77 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
78
79 const QString expressionString = parameterAsExpression( parameters, QStringLiteral( "EXPRESSION" ), context );
80
81 const bool ascending = parameterAsBoolean( parameters, QStringLiteral( "ASCENDING" ), context );
82 const bool nullsFirst = parameterAsBoolean( parameters, QStringLiteral( "NULLS_FIRST" ), context );
83
84 QString sinkId;
85 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, sinkId, source->fields(), source->wkbType(), source->sourceCrs() ) );
86 if ( !sink )
87 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
88
89 const long count = source->featureCount();
90 const double step = count > 0 ? 100.0 / count : 1;
91 int current = 0;
92
93 QgsFeatureRequest request;
94 request.addOrderBy( expressionString, ascending, nullsFirst );
95
96 QgsFeature inFeature;
98 while ( features.nextFeature( inFeature ) )
99 {
100 if ( feedback->isCanceled() )
101 {
102 break;
103 }
104 if ( !sink->addFeature( inFeature ) )
105 throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
106 feedback->setProgress( current * step );
107 current++;
108 }
109
110 QVariantMap outputs;
111 outputs.insert( QStringLiteral( "OUTPUT" ), sinkId );
112 return outputs;
113}
114
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
This class wraps a request for features to a vector layer (or directly its vector data provider).
QgsFeatureRequest & addOrderBy(const QString &expression, bool ascending=true)
Adds a new OrderByClause, appending it as the least important one.
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:56
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition qgsfeedback.h:54
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition qgsfeedback.h:63
Contains information about the context in which a processing algorithm is executed.
Custom exception class for processing related exceptions.
@ FlagSkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
Base class for providing feedback from a processing algorithm.
A boolean parameter for processing algorithms.
An expression parameter for processing algorithms.
A feature sink output for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.
@ TypeVector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...