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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.
105 lines
3.9 KiB
Python
105 lines
3.9 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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DeleteColumn.py
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---------------------
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Date : May 2010
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Copyright : (C) 2010 by Michael Minn
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Email : pyqgis at michaelminn 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__ = 'Michael Minn'
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__date__ = 'May 2010'
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__copyright__ = '(C) 2010, Michael Minn'
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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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QgsFeatureSink,
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QgsProcessingUtils,
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QgsProcessingParameterFeatureSource,
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QgsProcessingParameterFeatureSink,
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QgsProcessingParameterField,
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QgsProcessingOutputVectorLayer)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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class DeleteColumn(QgisAlgorithm):
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INPUT = 'INPUT'
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COLUMNS = 'COLUMN'
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OUTPUT = 'OUTPUT'
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def tags(self):
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return self.tr('drop,delete,remove,fields,columns,attributes').split(',')
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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.addParameter(QgsProcessingParameterFeatureSource(self.INPUT, self.tr('Input layer')))
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self.addParameter(QgsProcessingParameterField(self.COLUMNS,
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self.tr('Fields to drop'),
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None, self.INPUT, QgsProcessingParameterField.Any, True))
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self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Output layer')))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr("Output layer")))
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def name(self):
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return 'deletecolumn'
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def displayName(self):
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return self.tr('Drop field(s)')
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def processAlgorithm(self, parameters, context, feedback):
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source = self.parameterAsSource(parameters, self.INPUT, context)
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fields_to_delete = self.parameterAsFields(parameters, self.COLUMNS, context)
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fields = source.fields()
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field_indices = []
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# loop through twice - first we need to build up a list of original attribute indices
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for f in fields_to_delete:
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index = fields.lookupField(f)
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field_indices.append(index)
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# important - make sure we remove from the end so we aren't changing used indices as we go
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field_indices.sort(reverse=True)
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# this second time we make a cleaned version of the fields
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for index in field_indices:
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fields.remove(index)
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(sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
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fields, source.wkbType(), source.sourceCrs())
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features = source.getFeatures()
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total = 100.0 / source.featureCount() if source.featureCount() else 0
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for current, f in enumerate(features):
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if feedback.isCanceled():
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break
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attributes = f.attributes()
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for index in field_indices:
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del attributes[index]
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f.setAttributes(attributes)
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sink.addFeature(f, QgsFeatureSink.FastInsert)
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feedback.setProgress(int(current * total))
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return {self.OUTPUT: dest_id}
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