ruby-marc/ruby-marc — pull request #20 by jrochkind (2013-09-09 14:33:43+00:00)
Title: fields.freeze can make a Record immutable and avoid accidental reindex

What do you guys think about this solution, @rsinger, @billdueber ?

Basically based on rsinger's idea, but even further simplified, seems pretty correct to me. Completely backwards compat, doesn't get in your way if you don't need it, easy to understand, three lines of code.