sanya-dbms/processing/algs/qgis/SelectByExpression.py

"""
***************************************************************************
    SelectByExpression.py
    ---------------------
    Date                 : July 2014
    Copyright            : (C) 2014 by Michael Douchin
***************************************************************************
*                                                                         *
*   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.                                   *
*                                                                         *
***************************************************************************
"""

__author__ = 'Michael Douchin'
__date__ = 'July 2014'
__copyright__ = '(C) 2014, Michael Douchin'

from qgis.core import (QgsExpression,
                       QgsProcessing,
                       QgsVectorLayer,
                       QgsProcessingAlgorithm,
                       QgsProcessingException,
                       QgsProcessingParameterVectorLayer,
                       QgsProcessingParameterExpression,
                       QgsProcessingParameterEnum,
                       QgsProcessingOutputVectorLayer)
from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm


class SelectByExpression(QgisAlgorithm):
    INPUT = 'INPUT'
    EXPRESSION = 'EXPRESSION'
    OUTPUT = 'OUTPUT'
    METHOD = 'METHOD'

    def group(self):
        return self.tr('Vector selection')

    def groupId(self):
        return 'vectorselection'

    def __init__(self):
        super().__init__()

    def flags(self):
        return super().flags() | QgsProcessingAlgorithm.FlagNoThreading | QgsProcessingAlgorithm.FlagNotAvailableInStandaloneTool

    def initAlgorithm(self, config=None):
        self.methods = [self.tr('creating new selection'),
                        self.tr('adding to current selection'),
                        self.tr('removing from current selection'),
                        self.tr('selecting within current selection')]

        self.addParameter(QgsProcessingParameterVectorLayer(self.INPUT, self.tr('Input layer'), types=[QgsProcessing.TypeVector]))

        self.addParameter(QgsProcessingParameterExpression(self.EXPRESSION,
                                                           self.tr('Expression'), parentLayerParameterName=self.INPUT))
        self.addParameter(QgsProcessingParameterEnum(self.METHOD,
                                                     self.tr('Modify current selection by'), self.methods, defaultValue=0))

        self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr('Selected (attribute)')))

    def name(self):
        return 'selectbyexpression'

    def displayName(self):
        return self.tr('Select by expression')

    def processAlgorithm(self, parameters, context, feedback):
        layer = self.parameterAsVectorLayer(parameters, self.INPUT, context)

        method = self.parameterAsEnum(parameters, self.METHOD, context)
        if method == 0:
            behavior = QgsVectorLayer.SetSelection
        elif method == 1:
            behavior = QgsVectorLayer.AddToSelection
        elif method == 2:
            behavior = QgsVectorLayer.RemoveFromSelection
        elif method == 3:
            behavior = QgsVectorLayer.IntersectSelection

        expression = self.parameterAsString(parameters, self.EXPRESSION, context)
        qExp = QgsExpression(expression)
        if qExp.hasParserError():
            raise QgsProcessingException(qExp.parserErrorString())

        layer.selectByExpression(expression, behavior)

        return {self.OUTPUT: parameters[self.INPUT]}