Use of column.name instead of index does not seem to work

I have set up names in my columnDefs as suggested:

     "columnDefs": [
         { "name":             'group',     "targets": [ 0 ] },
         { "name":             'user',      "targets": [ 1 ] },
         { "name":             'comment',   "targets": [ 2 ] },

I now want to use these instead of column indices to make
code more readable (which I thought was the purpose of the feature):

var api = oTable.api()

api.rows().eq(0).each( function( idx )
{
       var row_data = api.row( idx ).data()

At this point however, data.group, data.user and data.comment are all undefined,
while data[0], data[1], data[2] are populated.

Have I missed something?