[Qgis-developer] Changes to a newly created memory layer are affecting the original layer from which it was copied

[Nyall Dawson]

On 16 Mar 2016 20:56, "Tom Chadwin" <tom.chadwin at nnpa.org.uk> wrote:
>

> def writeTmpLayer(layer, popup):
>     usedFields = getUsedFields(layer)
>     if popup != ALL_ATTRIBUTES:
>         uri = TYPE_MAP[layer.wkbType()]
>         crs = layer.crs()
>         if crs.isValid():
>             uri += '?crs=' + crs.authid()
>         if popup != NO_POPUP:
>             usedFields.append(popup)
>         for field in usedFields:
>             fieldType = layer.pendingFields().field(field).type()
>             fieldType = "double" if (fieldType == QVariant.Double or
>                                      fieldType == QVariant.Int) else (
>                                         "string")
>             uri += '&field=' + unicode(field) + ":" + fieldType
>         newlayer = QgsVectorLayer(uri, layer.name(), 'memory')
>         writer = newlayer.dataProvider()
>         outFeat = QgsFeature()
>         for feature in layer.getFeatures():
>             outFeat.setGeometry(feature.geometry())
>             attrs = [feature[f] for f in usedFields]
>             if attrs:
>                 outFeat.setAttributes(attrs)
>             writer.addFeatures([outFeat])
>         layer = newlayer
>     return layer
>
> The snippet which calls the function above and is meant to add the fields
to
> the memory layer is:
>
> if (layer.type() == layer.VectorLayer)
>     cleanLayer = writeTmpLayer(layer, popup)
>     if is25d(layer, canvas):
>         provider = cleanLayer.dataProvider()
>         provider.addAttributes([QgsField("height", QVariant.Double),
>                                 QgsField("wallColor", QVariant.String),
>                                 QgsField("roofColor",
>                                          QVariant.String)])
>         cleanLayer.updateFields()

>

If popup == ALL_ATTRIBUTES then your writeTmpLayer function is returning
the original layer.

Nyall
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