New method to duplicate a vector layer in memory and optionally add it to the map registry

ptormene · alexbruy · commit 71e57a7a2570 · 2014-03-25T19:53:32.000+02:00
diff --git a/python/plugins/processing/tools/vector.py b/python/plugins/processing/tools/vector.py
@@ -25,6 +25,8 @@
 
 __revision__ = '$Format:%H$'
 
+import uuid
+
 from PyQt4.QtCore import *
 from qgis.core import *
 from processing.core.ProcessingConfig import ProcessingConfig
@@ -274,3 +276,65 @@ def combineVectorFields(layerA, layerB):
         fields.append(field)
 
     return fields
+
+
+def duplicate_in_memory(layer, new_name='', add_to_registry=False):
+    """
+    Return a memory copy of a layer
+
+    :param layer: QgsVectorLayer that shall be copied to memory.
+    :type layer: QgsVectorLayer
+
+    :param new_name: The name of the copied layer.
+    :type new_name: str
+
+    :param add_to_registry: if True, the new layer will be added to
+    the QgsMapRegistry
+    :type: bool
+
+    :returns: An in-memory copy of a layer.
+    :rtype: QgsMapLayer
+
+    """
+    if new_name is '':
+        new_name = layer.name() + ' TMP'
+
+    if layer.type() == QgsMapLayer.VectorLayer:
+        v_type = layer.geometryType()
+        if v_type == QGis.Point:
+            type_str = 'Point'
+        elif v_type == QGis.Line:
+            type_str = 'Line'
+        elif v_type == QGis.Polygon:
+            type_str = 'Polygon'
+        else:
+            raise RuntimeError('Layer is whether Point nor '
+                               'Line nor Polygon')
+    else:
+        raise RuntimeError('Layer is not a VectorLayer')
+
+    crs = layer.crs().authid().lower()
+    my_uuid = str(uuid.uuid4())
+    uri = '%s?crs=%s&index=yes&uuid=%s' % (type_str, crs, my_uuid)
+    mem_layer = QgsVectorLayer(uri, new_name, 'memory')
+    mem_provider = mem_layer.dataProvider()
+
+    provider = layer.dataProvider()
+    v_fields = provider.fields()
+
+    fields = []
+    for i in v_fields:
+        fields.append(i)
+
+    mem_provider.addAttributes(fields)
+
+    for ft in provider.getFeatures():
+        mem_provider.addFeatures([ft])
+
+    if add_to_registry:
+        if mem_layer.isValid():
+            QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
+        else:
+            raise RuntimeError('Layer invalid')
+
+    return mem_layer
