22QString QgsExtractByAttributeAlgorithm::name()
const
24 return QStringLiteral(
"extractbyattribute" );
27QString QgsExtractByAttributeAlgorithm::displayName()
const
29 return QObject::tr(
"Extract by attribute" );
32QStringList QgsExtractByAttributeAlgorithm::tags()
const
34 return QObject::tr(
"extract,filter,attribute,value,contains,null,field" ).split(
',' );
37QString QgsExtractByAttributeAlgorithm::group()
const
39 return QObject::tr(
"Vector selection" );
42QString QgsExtractByAttributeAlgorithm::groupId()
const
44 return QStringLiteral(
"vectorselection" );
47void QgsExtractByAttributeAlgorithm::initAlgorithm(
const QVariantMap & )
51 addParameter(
new QgsProcessingParameterField( QStringLiteral(
"FIELD" ), QObject::tr(
"Selection attribute" ), QVariant(), QStringLiteral(
"INPUT" ) ) );
59 << QObject::tr(
"begins with" )
60 << QObject::tr(
"contains" )
61 << QObject::tr(
"is null" )
62 << QObject::tr(
"is not null" )
63 << QObject::tr(
"does not contain" ),
false, 0 ) );
70 addParameter( failOutput );
73QString QgsExtractByAttributeAlgorithm::shortHelpString()
const
75 return QObject::tr(
"This algorithm creates a new vector layer that only contains matching features from an input layer. "
76 "The criteria for adding features to the resulting layer is defined based on the values "
77 "of an attribute from the input layer." );
80QgsExtractByAttributeAlgorithm *QgsExtractByAttributeAlgorithm::createInstance()
const
82 return new QgsExtractByAttributeAlgorithm();
87 std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral(
"INPUT" ), context ) );
91 const QString fieldName = parameterAsString( parameters, QStringLiteral(
"FIELD" ), context );
92 const Operation op =
static_cast< Operation
>( parameterAsEnum( parameters, QStringLiteral(
"OPERATOR" ), context ) );
93 const QString value = parameterAsString( parameters, QStringLiteral(
"VALUE" ), context );
95 QString matchingSinkId;
96 std::unique_ptr< QgsFeatureSink > matchingSink( parameterAsSink( parameters, QStringLiteral(
"OUTPUT" ), context, matchingSinkId, source->fields(),
97 source->wkbType(), source->sourceCrs() ) );
101 QString nonMatchingSinkId;
102 std::unique_ptr< QgsFeatureSink > nonMatchingSink( parameterAsSink( parameters, QStringLiteral(
"FAIL_OUTPUT" ), context, nonMatchingSinkId, source->fields(),
103 source->wkbType(), source->sourceCrs() ) );
105 const int idx = source->fields().lookupField( fieldName );
107 throw QgsProcessingException( QObject::tr(
"Field '%1' was not found in INPUT source" ).arg( fieldName ) );
109 const QMetaType::Type fieldType = source->fields().at( idx ).type();
111 if ( fieldType != QMetaType::Type::QString && ( op == BeginsWith || op == Contains || op == DoesNotContain ) )
117 method = QObject::tr(
"begins with" );
120 method = QObject::tr(
"contains" );
123 method = QObject::tr(
"does not contain" );
130 throw QgsProcessingException( QObject::tr(
"Operator '%1' can be used only with string fields." ).arg( method ) );
139 expr = QStringLiteral(
"%1 = %3" ).arg( fieldRef, quotedVal );
142 expr = QStringLiteral(
"%1 != %3" ).arg( fieldRef, quotedVal );
145 expr = QStringLiteral(
"%1 > %3" ).arg( fieldRef, quotedVal );
147 case GreaterThanEqualTo:
148 expr = QStringLiteral(
"%1 >= %3" ).arg( fieldRef, quotedVal );
151 expr = QStringLiteral(
"%1 < %3" ).arg( fieldRef, quotedVal );
153 case LessThanEqualTo:
154 expr = QStringLiteral(
"%1 <= %3" ).arg( fieldRef, quotedVal );
157 expr = QStringLiteral(
"%1 LIKE '%2%'" ).arg( fieldRef, value );
160 expr = QStringLiteral(
"%1 LIKE '%%2%'" ).arg( fieldRef, value );
163 expr = QStringLiteral(
"%1 IS NULL" ).arg( fieldRef );
166 expr = QStringLiteral(
"%1 IS NOT NULL" ).arg( fieldRef );
169 expr = QStringLiteral(
"%1 NOT LIKE '%%2%'" ).arg( fieldRef, value );
174 if ( expression.hasParserError() )
179 QgsExpressionContext expressionContext = createExpressionContext( parameters, context, source.get() );
181 const long count = source->featureCount();
183 const double step = count > 0 ? 100.0 / count : 1;
186 if ( !nonMatchingSink )
203 throw QgsProcessingException( writeFeatureError( matchingSink.get(), parameters, QStringLiteral(
"OUTPUT" ) ) );
212 expressionContext.
setFields( source->fields() );
213 expression.prepare( &expressionContext );
225 if ( expression.evaluate( &expressionContext ).toBool() )
228 throw QgsProcessingException( writeFeatureError( matchingSink.get(), parameters, QStringLiteral(
"OUTPUT" ) ) );
233 throw QgsProcessingException( writeFeatureError( nonMatchingSink.get(), parameters, QStringLiteral(
"FAIL_OUTPUT" ) ) );
243 outputs.insert( QStringLiteral(
"OUTPUT" ), matchingSinkId );
244 if ( nonMatchingSink )
245 outputs.insert( QStringLiteral(
"FAIL_OUTPUT" ), nonMatchingSinkId );
@ Vector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
@ VectorAnyGeometry
Any vector layer with geometry.
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
Expression contexts are used to encapsulate the parameters around which a QgsExpression should be eva...
void setFeature(const QgsFeature &feature)
Convenience function for setting a feature for the context.
void setFields(const QgsFields &fields)
Convenience function for setting a fields for the context.
Class for parsing and evaluation of expressions (formerly called "search strings").
static QString quotedValue(const QVariant &value)
Returns a string representation of a literal value, including appropriate quotations where required.
static QString quotedColumnRef(QString name)
Returns a quoted column reference (in double quotes)
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
Fetch next feature and stores in f, returns true on success.
This class wraps a request for features to a vector layer (or directly its vector data provider).
QgsFeatureRequest & setFilterExpression(const QString &expression)
Set the filter expression.
QgsFeatureRequest & setExpressionContext(const QgsExpressionContext &context)
Sets the expression context used to evaluate filter expressions.
@ FastInsert
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
bool isCanceled() const
Tells whether the operation has been canceled already.
void setProgress(double progress)
Sets the current progress for the feedback object.
Contains information about the context in which a processing algorithm is executed.
void setCreateByDefault(bool createByDefault)
Sets whether the destination should be created by default.
Custom exception class for processing related exceptions.
Base class for providing feedback from a processing algorithm.
An enum based parameter for processing algorithms, allowing for selection from predefined values.
A feature sink output for processing algorithms.
An input feature source (such as vector layers) parameter for processing algorithms.
A vector layer or feature source field parameter for processing algorithms.
A string parameter for processing algorithms.