3

As far as I see, on QgsMapLayerRegistry.instance() there is a method to select layers:

mapLayersByName(Qstring)

and the method

mapLayer(QString)

respectively, wich accesses a layer by its id.

As the name says, mapLayersByName() selects layers by their name in the legend, wich causes scripts or plugins to fail if a user renames a layer/table (i.e. renaming a table '160520_parcels' to 'Parcels').

So is there a way to access a layer by the name of it's origining table in PyQGIS?

update

something like ...

def selectLayerByOriginalName(tablename):
    # return layers whose orininal names start with 'tablename'
    llist = []
    for l in QgsMapLayerRegistry.instance().mapLayers().values():
        if tablename in l.id():
           if l.id().index(tablename) == 0:
               llist.append(lyr)
    return llist

... works, but is there a more convenient approach?

  • 2
    There is an OriginalName() method (docs) in QgsMapLayer, but strangely it is altered once the user changes the layer name. I agree that using the id() (extracting the first part of it) seems to be the only way. However, using your code, looking for a "Roads2" layer, a layer called "Roads" would also match and enter the 2 ifs. I'd rather try to remove the timestamp. – Germán Carrillo Jun 1 '16 at 14:20
1

You can do it this way:

def get_layer_by_tablename(self, tablename):
    """ Iterate over all layers and get the one with selected @tablename """

    # Check if we have any layer loaded
    layers = self.iface.legendInterface().layers()
    if len(layers) == 0:
        return None

    # Iterate over all layers
    layer = None
    for cur_layer in layers:
        uri_table = self.get_layer_source_table_name(cur_layer)
        if uri_table is not None and uri_table == tablename:
            layer = cur_layer
            break

    if layer is None:
       print ("Layer not found")

    return layer


def get_layer_source_table_name(self, layer):
    """ Get table or view name of selected layer """

    if layer is None:
        return None

    uri_table = None
    uri = layer.dataProvider().dataSourceUri().lower()
    pos_ini = uri.find('table=')
    pos_end_schema = uri.rfind('.')
    pos_fi = uri.find('" ')
    if pos_ini <> -1 and pos_fi <> -1:
        uri_table = uri[pos_end_schema+2:pos_fi]

    return uri_table  

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