Python QgsExpressionContextUtils.globalProjectLayerScopes方法代码示例

# 需要导入模块: from qgis.core import QgsExpressionContextUtils [as 别名]
# 或者: from qgis.core.QgsExpressionContextUtils import globalProjectLayerScopes [as 别名]
    def processAlgorithm(self, feedback):
        layer = dataobjects.getLayerFromString(
            self.getParameterValue(self.INPUT_LAYER))

        geometry_type = self.getParameterValue(self.OUTPUT_GEOMETRY)
        wkb_type = None
        if geometry_type == 0:
            wkb_type = QgsWkbTypes.Polygon
        elif geometry_type == 1:
            wkb_type = QgsWkbTypes.LineString
        else:
            wkb_type = QgsWkbTypes.Point
        if self.getParameterValue(self.WITH_Z):
            wkb_type = QgsWkbTypes.addZ(wkb_type)
        if self.getParameterValue(self.WITH_M):
            wkb_type = QgsWkbTypes.addM(wkb_type)

        writer = self.getOutputFromName(
            self.OUTPUT_LAYER).getVectorWriter(
                layer.fields(),
                wkb_type,
                layer.crs())

        expression = QgsExpression(self.getParameterValue(self.EXPRESSION))
        if expression.hasParserError():
            raise GeoAlgorithmExecutionException(expression.parserErrorString())

        exp_context = QgsExpressionContext(QgsExpressionContextUtils.globalProjectLayerScopes(layer))

        if not expression.prepare(exp_context):
            raise GeoAlgorithmExecutionException(
                self.tr('Evaluation error: {0}').format(expression.evalErrorString()))

        features = vector.features(layer)
        total = 100.0 / len(features)
        for current, input_feature in enumerate(features):
            output_feature = input_feature

            exp_context.setFeature(input_feature)
            value = expression.evaluate(exp_context)
            if expression.hasEvalError():
                raise GeoAlgorithmExecutionException(
                    self.tr('Evaluation error: {0}').format(expression.evalErrorString()))

            if not value:
                output_feature.setGeometry(QgsGeometry())
            else:
                if not isinstance(value, QgsGeometry):
                    raise GeoAlgorithmExecutionException(
                        self.tr('{} is not a geometry').format(value))
                output_feature.setGeometry(value)

            writer.addFeature(output_feature)
            feedback.setProgress(int(current * total))

        del writer

# 需要导入模块: from qgis.core import QgsExpressionContextUtils [as 别名]
# 或者: from qgis.core.QgsExpressionContextUtils import globalProjectLayerScopes [as 别名]
 def initContext(self):
     exp_context = self.builder.expressionContext()
     exp_context.appendScopes(QgsExpressionContextUtils.globalProjectLayerScopes(self.layer))
     exp_context.lastScope().setVariable("row_number", 1)
     exp_context.setHighlightedVariables(["row_number"])
     self.builder.setExpressionContext(exp_context)

# 需要导入模块: from qgis.core import QgsExpressionContextUtils [as 别名]
# 或者: from qgis.core.QgsExpressionContextUtils import globalProjectLayerScopes [as 别名]
    def processAlgorithm(self, parameters, context, feedback):
        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT_LAYER), context)
        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)

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

        writer = output.getVectorWriter(fields, layer.wkbType(), layer.crs(), context)

        exp = QgsExpression(formula)

        da = QgsDistanceArea()
        da.setSourceCrs(layer.crs())
        da.setEllipsoid(QgsProject.instance().ellipsoid())
        exp.setGeomCalculator(da)
        exp.setDistanceUnits(QgsProject.instance().distanceUnits())
        exp.setAreaUnits(QgsProject.instance().areaUnits())

        exp_context = QgsExpressionContext(QgsExpressionContextUtils.globalProjectLayerScopes(layer))

        if not exp.prepare(exp_context):
            raise GeoAlgorithmExecutionException(
                self.tr('Evaluation error: {0}').format(exp.evalErrorString()))

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

        error = ''
        calculationSuccess = True

        features = QgsProcessingUtils.getFeatures(layer, context)
        total = 100.0 / layer.featureCount() if layer.featureCount() else 0

        rownum = 1
        for current, f in enumerate(features):
            rownum = current + 1
            exp_context.setFeature(f)
            exp_context.lastScope().setVariable("row_number", rownum)
            value = exp.evaluate(exp_context)
            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, QgsFeatureSink.FastInsert)

            feedback.setProgress(int(current * total))
        del writer

        if not calculationSuccess:
            raise GeoAlgorithmExecutionException(
                self.tr('An error occurred while evaluating the calculation '
                        'string:\n{0}').format(error))