QGIS/python/plugins/processing/algs/FieldsCalculator.py

# -*- coding: utf-8 -*-

"""
***************************************************************************
    FieldsCalculator.py
    ---------------------
    Date                 : August 2012
    Copyright            : (C) 2012 by Victor Olaya
    Email                : volayaf at gmail dot com
***************************************************************************
*                                                                         *
*   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__ = 'Victor Olaya'
__date__ = 'August 2012'
__copyright__ = '(C) 2012, Victor Olaya'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

from PyQt4.QtCore import *
from qgis.core import *
from processing import interface
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import \
        GeoAlgorithmExecutionException
from processing.parameters.ParameterVector import ParameterVector
from processing.parameters.ParameterString import ParameterString
from processing.parameters.ParameterNumber import ParameterNumber
from processing.parameters.ParameterBoolean import ParameterBoolean
from processing.parameters.ParameterSelection import ParameterSelection
from processing.outputs.OutputVector import OutputVector
from processing.tools import dataobjects, vector

from processing.algs.ui.FieldsCalculatorDialog import FieldsCalculatorDialog

class FieldsCalculator(GeoAlgorithm):

    INPUT_LAYER = 'INPUT_LAYER'
    NEW_FIELD = 'NEW_FIELD'
    FIELD_NAME = 'FIELD_NAME'
    FIELD_TYPE = 'FIELD_TYPE'
    FIELD_LENGTH = 'FIELD_LENGTH'
    FIELD_PRECISION = 'FIELD_PRECISION'
    FORMULA = 'FORMULA'
    OUTPUT_LAYER = 'OUTPUT_LAYER'

    TYPE_NAMES = ['Float', 'Integer', 'String', 'Date']
    TYPES = [QVariant.Double, QVariant.Int, QVariant.String, QVariant.Date]

    def defineCharacteristics(self):
        self.name = 'Field calculator'
        self.group = 'Vector table tools'
        self.addParameter(ParameterVector(self.INPUT_LAYER, 'Input layer',
                          [ParameterVector.VECTOR_TYPE_ANY], False))
        self.addParameter(ParameterString(self.FIELD_NAME, 'Result field name'
                          ))
        self.addParameter(ParameterSelection(self.FIELD_TYPE, 'Field type',
                          self.TYPE_NAMES))
        self.addParameter(ParameterNumber(self.FIELD_LENGTH, 'Field length',
                          1, 255, 10))
        self.addParameter(ParameterNumber(self.FIELD_PRECISION,
                          'Field precision', 0, 15, 3))
        self.addParameter(ParameterBoolean(self.NEW_FIELD,
                          'Create new field', True))
        self.addParameter(ParameterString(self.FORMULA, 'Formula'))
        self.addOutput(OutputVector(self.OUTPUT_LAYER, 'Output layer'))

    def processAlgorithm(self, progress):
        layer = dataobjects.getObjectFromUri(
                self.getParameterValue(self.INPUT_LAYER))
        fieldName = self.getParameterValue(self.FIELD_NAME)
        fieldType = self.TYPES[self.getParameterValue(self.FIELD_TYPE)]
        width = self.getParameterValue(self.FIELD_LENGTH)
        precision = self.getParameterValue(self.FIELD_PRECISION)
        newField = self.getParameterValue(self.NEW_FIELD)
        formula = self.getParameterValue(self.FORMULA)

        output = self.getOutputFromName(self.OUTPUT_LAYER)

        provider = layer.dataProvider()
        fields = layer.pendingFields()
        if newField:
            fields.append(QgsField(fieldName, fieldType, '', width, precision))

        writer = output.getVectorWriter(fields, provider.geometryType(),
                                        layer.crs())

        exp = QgsExpression(formula)

        da = QgsDistanceArea()
        da.setSourceCrs(layer.crs().srsid())
        canvas = interface.iface.mapCanvas()
        da.setEllipsoidalMode(canvas.mapRenderer().hasCrsTransformEnabled())
        da.setEllipsoid(QgsProject.instance().readEntry('Measure',
                                                        '/Ellipsoid',
                                                        GEO_NONE)[0])
        exp.setGeomCalculator(da)

        if not exp.prepare(layer.pendingFields()):
            raise GeoAlgorithmExecutionException(
                'Evaluation error: ' + exp.evalErrorString())

        outFeature = QgsFeature()
        outFeature.initAttributes(len(fields))
        outFeature.setFields(fields)

        error = ''
        calculationSuccess = True

        current = 0
        features = vector.features(layer)
        total = 100.0 / len(features)

        rownum = 1
        for f in features:
            exp.setCurrentRowNumber(rownum)
            value = exp.evaluate(f)
            if exp.hasEvalError():
                calculationSuccess = False
                error = exp.evalErrorString()
                break
            else:
                outFeature.setGeometry(f.geometry())
                for fld in f.fields():
                    outFeature[fld.name()] = f[fld.name()]
                outFeature[fieldName] = value
                writer.addFeature(outFeature)

            current += 1
            progress.setPercentage(int(current * total))
        del writer

        if not calculationSuccess:
            raise GeoAlgorithmExecutionException(
                'An error occured while evaluating the calculation '
                'string:\n' + error)


    def checkParameterValuesBeforeExecuting(self):
        newField = self.getParameterValue(self.NEW_FIELD)
        fieldName = self.getParameterValue(self.FIELD_NAME)
        if newField and len(fieldName) == 0:
            raise GeoAlgorithmExecutionException('Field name is not set. '
                                                 'Please enter a field name')

        outputName = self.getOutputValue(self.OUTPUT_LAYER)
        if outputName == '':
            raise GeoAlgorithmExecutionException('Output is not set. '
                'Please specify valid filename')


    def getCustomParametersDialog(self):
        return FieldsCalculatorDialog(self)