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1e13d733c2
initAlgorithm() method This allows 2 benefits: - algorithms can be subclassed and have subclasses add additional parameters/outputs to the algorithm. With the previous approach of declaring parameters/outputs in the constructor, it's not possible to call virtual methods to add additional parameters/ outputs (since you can't call virtual methods from a constructor). - initAlgorithm takes a variant map argument, allowing the algorithm to dynamically adjust its declared parameters and outputs according to this configuration map. This potentially allows model algorithms which can be configured to have variable numbers of parameters and outputs at run time. E.g. a "router" algorithm which directs features to one of any number of output sinks depending on some user configured criteria.
173 lines
7.0 KiB
Python
173 lines
7.0 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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FieldsCalculator.py
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---------------------
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Date : August 2012
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Copyright : (C) 2012 by Victor Olaya
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Email : volayaf at gmail dot com
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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__ = 'Victor Olaya'
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__date__ = 'August 2012'
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__copyright__ = '(C) 2012, Victor Olaya'
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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.PyQt.QtCore import QVariant
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from qgis.core import (QgsExpression,
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QgsExpressionContext,
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QgsExpressionContextUtils,
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QgsFeature,
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QgsFeatureSink,
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QgsField,
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QgsDistanceArea,
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QgsProject,
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QgsApplication,
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QgsProcessingUtils)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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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 ParameterString
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from processing.core.parameters import ParameterNumber
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from processing.core.parameters import ParameterBoolean
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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 .ui.FieldsCalculatorDialog import FieldsCalculatorDialog
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class FieldsCalculator(QgisAlgorithm):
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INPUT_LAYER = 'INPUT_LAYER'
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NEW_FIELD = 'NEW_FIELD'
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FIELD_NAME = 'FIELD_NAME'
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FIELD_TYPE = 'FIELD_TYPE'
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FIELD_LENGTH = 'FIELD_LENGTH'
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FIELD_PRECISION = 'FIELD_PRECISION'
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FORMULA = 'FORMULA'
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OUTPUT_LAYER = 'OUTPUT_LAYER'
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TYPES = [QVariant.Double, QVariant.Int, QVariant.String, QVariant.Date]
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def group(self):
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return self.tr('Vector table tools')
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def __init__(self):
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super().__init__()
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def initAlgorithm(self, config=None):
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self.type_names = [self.tr('Float'),
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self.tr('Integer'),
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self.tr('String'),
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self.tr('Date')]
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self.addParameter(ParameterVector(self.INPUT_LAYER,
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self.tr('Input layer')))
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self.addParameter(ParameterString(self.FIELD_NAME,
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self.tr('Result field name')))
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self.addParameter(ParameterSelection(self.FIELD_TYPE,
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self.tr('Field type'), self.type_names))
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self.addParameter(ParameterNumber(self.FIELD_LENGTH,
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self.tr('Field length'), 1, 255, 10))
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self.addParameter(ParameterNumber(self.FIELD_PRECISION,
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self.tr('Field precision'), 0, 15, 3))
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self.addParameter(ParameterBoolean(self.NEW_FIELD,
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self.tr('Create new field'), True))
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self.addParameter(ParameterString(self.FORMULA, self.tr('Formula')))
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self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Calculated')))
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def name(self):
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return 'fieldcalculator'
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def displayName(self):
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return self.tr('Field calculator')
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def processAlgorithm(self, parameters, context, feedback):
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layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT_LAYER), context)
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fieldName = self.getParameterValue(self.FIELD_NAME)
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fieldType = self.TYPES[self.getParameterValue(self.FIELD_TYPE)]
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width = self.getParameterValue(self.FIELD_LENGTH)
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precision = self.getParameterValue(self.FIELD_PRECISION)
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newField = self.getParameterValue(self.NEW_FIELD)
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formula = self.getParameterValue(self.FORMULA)
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output = self.getOutputFromName(self.OUTPUT_LAYER)
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fields = layer.fields()
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if newField:
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fields.append(QgsField(fieldName, fieldType, '', width, precision))
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writer = output.getVectorWriter(fields, layer.wkbType(), layer.crs(), context)
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exp = QgsExpression(formula)
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da = QgsDistanceArea()
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da.setSourceCrs(layer.crs())
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da.setEllipsoid(QgsProject.instance().ellipsoid())
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exp.setGeomCalculator(da)
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exp.setDistanceUnits(QgsProject.instance().distanceUnits())
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exp.setAreaUnits(QgsProject.instance().areaUnits())
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exp_context = QgsExpressionContext(QgsExpressionContextUtils.globalProjectLayerScopes(layer))
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if not exp.prepare(exp_context):
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raise GeoAlgorithmExecutionException(
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self.tr('Evaluation error: {0}').format(exp.evalErrorString()))
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outFeature = QgsFeature()
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outFeature.initAttributes(len(fields))
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outFeature.setFields(fields)
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error = ''
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calculationSuccess = True
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features = QgsProcessingUtils.getFeatures(layer, context)
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total = 100.0 / layer.featureCount() if layer.featureCount() else 0
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rownum = 1
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for current, f in enumerate(features):
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rownum = current + 1
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exp_context.setFeature(f)
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exp_context.lastScope().setVariable("row_number", rownum)
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value = exp.evaluate(exp_context)
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if exp.hasEvalError():
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calculationSuccess = False
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error = exp.evalErrorString()
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break
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else:
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outFeature.setGeometry(f.geometry())
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for fld in f.fields():
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outFeature[fld.name()] = f[fld.name()]
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outFeature[fieldName] = value
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writer.addFeature(outFeature, QgsFeatureSink.FastInsert)
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feedback.setProgress(int(current * total))
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del writer
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if not calculationSuccess:
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raise GeoAlgorithmExecutionException(
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self.tr('An error occurred while evaluating the calculation '
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'string:\n{0}').format(error))
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def checkParameterValues(self, parameters, context):
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newField = self.getParameterValue(self.NEW_FIELD)
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fieldName = self.getParameterValue(self.FIELD_NAME).strip()
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if newField and len(fieldName) == 0:
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return self.tr('Field name is not set. Please enter a field name')
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return super(FieldsCalculator, self).checkParameterValues(parameters, context)
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def createCustomParametersWidget(self, parent):
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return FieldsCalculatorDialog(self)
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