This gist was writen in 2012 and it was solving specific problem in Rails & SimpleForm. Some fellow developers were pointing out this may be out dated concept. That's why I advise everyone to read comment section bellow to have a full grasp of alternative solutions
other sources that may be helpful to understand why this may not be best idea:
ok, colleague pointed out that one can use also
ActiveRecord::ConnectionAdapters::Column.value_to_boolean("true")
...updating my gits, thx D.D.