How to sort a list in Scala by two fields?

rows.sortBy (row => row.lastName + row.firstName)

If you want to sort by the merged names, as in your question, or

rows.sortBy (row => (row.lastName, row.firstName))

if you first want to sort by lastName, then firstName; relevant for longer names (Wild, Wilder, Wilderman).

If you write

rows.sortBy(_.lastName + _.firstName)

with 2 underlines, the method expects two parameters:

<console>:14: error: wrong number of parameters; expected = 1
       rows.sortBy (_.lastName + _.firstName)
                               ^

rows.sortBy(r => (r.lastName, r.firstName))

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