Question

Case classes in Scala are standard classes enhanced with pattern-matching, equals, … (or am I wrong?). Moreover they require no “new” keyword for their instanciation. It seems to me that they are simpler to define than regular classes (or am I again wrong?).

There are lots of web pages telling where they should be used (mostly about pattern matchin). But where should they be avoided ? Why don’t we use them everywhere ?

Answer 1

There are many places where case classes are not adequate:

• When one wishes to hide the data structure.
• As part of a type hierarchy of more than two or three levels.
• When the constructor requires special considerations.
• When the extractor requires special considerations.
• When equality and hash code requires special considerations.

Sometimes these requirements show up late in the design, and requires one to convert a case class into a normal class. Since the benefits of a case class really aren’t all that great — aside from the few special cases they were specially made for — my own recommendation is not to make anything a case class unless there’s a clear use for it.

Or, in other words, do not overdesign.