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Algorithms and other processing code should use this method (instead of dataobjects.getLayerFromString) to retrieve layers from a string, as it considers the processing context and allows resolving strings to temporarily stored layers. This permits processing models to function correctly when intermediate results are stored as memory layers. Subsequent model algorithms can then access these temporary layers as inputs. All temporary layers will be removed when the context object is destroyed after the model algorithm is run.
96 lines
3.7 KiB
Python
96 lines
3.7 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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SelectByExpression.py
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---------------------
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Date : July 2014
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Copyright : (C) 2014 by Michael Douchin
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Michael Douchin'
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__date__ = 'July 2014'
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__copyright__ = '(C) 2014, Michael Douchin'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsApplication,
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QgsExpression,
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QgsVectorLayer)
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.core.parameters import ParameterVector
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from processing.core.parameters import ParameterSelection
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from processing.core.outputs import OutputVector
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.parameters import ParameterExpression
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from processing.tools import dataobjects
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class SelectByExpression(GeoAlgorithm):
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LAYERNAME = 'LAYERNAME'
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EXPRESSION = 'EXPRESSION'
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RESULT = 'RESULT'
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METHOD = 'METHOD'
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def icon(self):
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return QgsApplication.getThemeIcon("/providerQgis.svg")
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def svgIconPath(self):
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return QgsApplication.iconPath("providerQgis.svg")
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def group(self):
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return self.tr('Vector selection tools')
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def name(self):
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return 'selectbyexpression'
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def displayName(self):
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return self.tr('Select by expression')
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def defineCharacteristics(self):
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self.methods = [self.tr('creating new selection'),
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self.tr('adding to current selection'),
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self.tr('removing from current selection'),
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self.tr('selecting within current selection')]
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self.addParameter(ParameterVector(self.LAYERNAME,
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self.tr('Input Layer')))
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self.addParameter(ParameterExpression(self.EXPRESSION,
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self.tr("Expression"), parent_layer=self.LAYERNAME))
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self.addParameter(ParameterSelection(self.METHOD,
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self.tr('Modify current selection by'), self.methods, 0))
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self.addOutput(OutputVector(self.RESULT, self.tr('Selected (expression)'), True))
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def processAlgorithm(self, context, feedback):
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filename = self.getParameterValue(self.LAYERNAME)
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layer = dataobjects.QgsProcessingUtils.mapLayerFromString(filename, context)
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method = self.getParameterValue(self.METHOD)
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if method == 0:
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behavior = QgsVectorLayer.SetSelection
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elif method == 1:
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behavior = QgsVectorLayer.AddToSelection
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elif method == 2:
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behavior = QgsVectorLayer.RemoveFromSelection
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elif method == 3:
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behavior = QgsVectorLayer.IntersectSelection
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expression = self.getParameterValue(self.EXPRESSION)
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qExp = QgsExpression(expression)
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if qExp.hasParserError():
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raise GeoAlgorithmExecutionException(qExp.parserErrorString())
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layer.selectByExpression(expression, behavior)
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self.setOutputValue(self.RESULT, filename)
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