In Clojure, if you want a basic OOP behavior without killing yourself to fully implement Java classes and interfaces in Clojure, the preferred technique is to use records. Sometimes implementing protocols in records suits your needs, mostly due to speed of code execution. However, if you want polymorphism with your records, then multimethods are where it’s at.
Admittedly, multimethods are very flexible, so the technique I’ll show you is one of many techniques you could use. The basic pattern I use for inheritance with records, is to use the
derive command with keywords that are kept as a value in the record. For example,
type is used to track
isa relationships of
derive is used to set
::food as the parent of
::fruit . Notice the use of custom constructors to set default values for
type in the records.
I absolutely love the user razvan’s Clojure
defrecord example over at stackoverflow, so I copied it here. I know I’ll never find it again if I don’t. Look at the original over on stackoverflow at this link.