qgsalgorithmfieldcalculator.cpp

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/***************************************************************************
                         qgsalgorithmfieldcalculator.h
                         ----------------------
    begin                : September 2020
    copyright            : (C) 2020 by Ivan Ivanov
    email                : [email protected]
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
 
#include "qgsalgorithmfieldcalculator.h"
#include "qgsexpressioncontextutils.h"
 
 
QString QgsFieldCalculatorAlgorithm::name() const
{
  return QStringLiteral( "fieldcalculator" );
}
 
QString QgsFieldCalculatorAlgorithm::displayName() const
{
  return QObject::tr( "Field calculator" );
}
 
QStringList QgsFieldCalculatorAlgorithm::tags() const
{
  return QObject::tr( "field,calculator,vector" ).split( ',' );
}
 
QString QgsFieldCalculatorAlgorithm::group() const
{
  return QObject::tr( "Vector table" );
}
 
QString QgsFieldCalculatorAlgorithm::groupId() const
{
  return QStringLiteral( "vectortable" );
}
 
QString QgsFieldCalculatorAlgorithm::outputName() const
{
  return QObject::tr( "Calculated" );
}
 
QList<int> QgsFieldCalculatorAlgorithm::inputLayerTypes() const
{
  return QList<int>() << QgsProcessing::TypeVector;
}
 
QgsProcessingFeatureSource::Flag QgsFieldCalculatorAlgorithm::sourceFlags() const
{
  return QgsProcessingFeatureSource::FlagSkipGeometryValidityChecks;
}
 
void QgsFieldCalculatorAlgorithm::initParameters( const QVariantMap &configuration )
{
  Q_UNUSED( configuration );
 
  const QStringList fieldTypes = QStringList( {QObject::tr( "Float" ), QObject::tr( "Integer" ), QObject::tr( "String" ), QObject::tr( "Date" ) } );
 
  std::unique_ptr< QgsProcessingParameterString > fieldName = std::make_unique< QgsProcessingParameterString > ( QStringLiteral( "FIELD_NAME" ), QObject::tr( "Field name" ), QVariant(), false );
  std::unique_ptr< QgsProcessingParameterEnum > fieldType = std::make_unique< QgsProcessingParameterEnum > ( QStringLiteral( "FIELD_TYPE" ), QObject::tr( "Result field type" ), fieldTypes, false, 0 );
  std::unique_ptr< QgsProcessingParameterNumber > fieldLength = std::make_unique< QgsProcessingParameterNumber > ( QStringLiteral( "FIELD_LENGTH" ), QObject::tr( "Result field length" ), QgsProcessingParameterNumber::Integer, QVariant( 0 ), false, 0 );
  std::unique_ptr< QgsProcessingParameterNumber > fieldPrecision = std::make_unique< QgsProcessingParameterNumber > ( QStringLiteral( "FIELD_PRECISION" ), QObject::tr( "Result field precision" ), QgsProcessingParameterNumber::Integer, QVariant( 0 ), false, 0 );
  std::unique_ptr< QgsProcessingParameterExpression > expression = std::make_unique< QgsProcessingParameterExpression> ( QStringLiteral( "FORMULA" ), QObject::tr( "Formula" ), QVariant(), QStringLiteral( "INPUT" ), false );
 
  expression->setMetadata( QVariantMap( {{"inlineEditor", true}} ) );
 
  addParameter( fieldName.release() );
  addParameter( fieldType.release() );
  addParameter( fieldLength.release() );
  addParameter( fieldPrecision.release() );
  addParameter( expression.release() );
}
 
QgsFields QgsFieldCalculatorAlgorithm::outputFields( const QgsFields & ) const
{
  return mFields;
}
 
QString QgsFieldCalculatorAlgorithm::shortHelpString() const
{
  return QObject::tr( "This algorithm computes a new vector layer with the same features of the input layer, "
                      "but either overwriting an existing attribute or adding an additional attribute. The values of this field "
                      "are computed from each feature using an expression, based on the properties and attributes of the feature. "
                      "Note that if \"Field name\" is an existing field in the layer then all the rest of the field settings are ignored." );
}
 
QgsFieldCalculatorAlgorithm *QgsFieldCalculatorAlgorithm::createInstance() const
{
  return new QgsFieldCalculatorAlgorithm();
}
 
 
bool QgsFieldCalculatorAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  std::unique_ptr< QgsProcessingFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
 
  if ( !source )
    throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
 
  QList<QVariant::Type> fieldTypes( {QVariant::Double, QVariant::Int, QVariant::String, QVariant::Date} );
 
  // prepare fields
  const int fieldTypeIdx = parameterAsInt( parameters, QStringLiteral( "FIELD_TYPE" ), context );
  const int fieldLength = parameterAsInt( parameters, QStringLiteral( "FIELD_LENGTH" ), context );
  const int fieldPrecision = parameterAsInt( parameters, QStringLiteral( "FIELD_PRECISION" ), context );
  const QString fieldName = parameterAsString( parameters, QStringLiteral( "FIELD_NAME" ), context );
 
  const QVariant::Type fieldType = fieldTypes[fieldTypeIdx];
 
  if ( fieldName.isEmpty() )
    throw QgsProcessingException( QObject::tr( "Field name must not be an empty string" ) );
 
  const QgsField field(
    fieldName,
    fieldType,
    QString(),
    fieldLength,
    fieldPrecision
  );
 
  mFields = source->fields();
 
  const int fieldIdx = mFields.indexFromName( field.name() );
 
  if ( fieldIdx < 0 )
  {
    mFields.append( field );
  }
  else
  {
    feedback->pushWarning( QObject::tr( "Field name %1 already exists and will be replaced" ).arg( field.name() ) );
  }
 
  const QString dest;
 
  mFieldIdx = mFields.lookupField( field.name() );
 
  // prepare expression
  const QString expressionString = parameterAsString( parameters, QStringLiteral( "FORMULA" ), context );
  mExpressionContext = createExpressionContext( parameters, context, source.get() );
  mExpression = QgsExpression( expressionString );
  mDa.setSourceCrs( source->sourceCrs(), context.transformContext() );
  mDa.setEllipsoid( context.ellipsoid() );
 
  mExpression.setGeomCalculator( &mDa );
  mExpression.setDistanceUnits( context.distanceUnit() );
  mExpression.setAreaUnits( context.areaUnit() );
 
  if ( mExpression.hasParserError() )
    throw QgsProcessingException( QObject::tr( "Parser error with formula expression \"%2\": %3" )
                                  .arg( expressionString, mExpression.parserErrorString() ) );
 
  mExpression.prepare( &mExpressionContext );
 
  return true;
}
 
QgsFeatureList QgsFieldCalculatorAlgorithm::processFeature( const QgsFeature &feature, QgsProcessingContext &, QgsProcessingFeedback * )
{
  QgsAttributes attributes( mFields.size() );
  const QStringList fieldNames = mFields.names();
  for ( const QString &fieldName : fieldNames )
  {
    const int attributeIndex = feature.fieldNameIndex( fieldName );
 
    if ( attributeIndex >= 0 )
      attributes[attributeIndex] = feature.attribute( fieldName );
  }
 
  if ( mExpression.isValid() )
  {
    mExpressionContext.setFeature( feature );
    mExpressionContext.lastScope()->setVariable( QStringLiteral( "row_number" ), mRowNumber );
 
    const QVariant value = mExpression.evaluate( &mExpressionContext );
 
    if ( mExpression.hasEvalError() )
    {
      throw QgsProcessingException( QObject::tr( "Evaluation error in expression \"%1\": %2" )
                                    .arg( mExpression.expression(), mExpression.evalErrorString() ) );
    }
 
    attributes[mFieldIdx] = value;
  }
  else
  {
    attributes[mFieldIdx] = QVariant();
  }
 
  QgsFeature f = feature;
  f.setAttributes( attributes );
  mRowNumber++;
  return QgsFeatureList() << f;
}
 
bool QgsFieldCalculatorAlgorithm::supportInPlaceEdit( const QgsMapLayer *layer ) const
{
  Q_UNUSED( layer )
  return false;
}