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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.
73 lines
2.6 KiB
Python
73 lines
2.6 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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TruncateTable.py
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-----------------------
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Date : January 2017
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Copyright : (C) 2017 by Nyall Dawson
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Email : nyall dot dawson 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__ = 'Nyall Dawson'
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__date__ = 'January 2017'
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__copyright__ = '(C) 2017, Nyall Dawson'
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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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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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from processing.core.parameters import ParameterTable
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from processing.core.outputs import OutputVector
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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class TruncateTable(QgisAlgorithm):
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INPUT = 'INPUT'
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OUTPUT = 'OUTPUT'
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def tags(self):
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return self.tr('empty,delete,layer,clear,features').split(',')
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def group(self):
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return self.tr('Vector general 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(ParameterTable(self.INPUT,
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self.tr('Input Layer')))
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self.addOutput(OutputVector(self.OUTPUT,
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self.tr('Truncated layer'), True))
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def name(self):
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return 'truncatetable'
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def displayName(self):
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return self.tr('Truncate table')
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def processAlgorithm(self, parameters, context, feedback):
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file_name = self.getParameterValue(self.INPUT)
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layer = QgsProcessingUtils.mapLayerFromString(file_name, context)
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provider = layer.dataProvider()
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if not provider.truncate():
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raise GeoAlgorithmExecutionException(
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self.tr('Could not truncate table.'))
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self.setOutputValue(self.OUTPUT, file_name)
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