Getting Clojure

Record Confusion

If you’re coming to Clojure from an object-oriented language, then this record and protocol talk probably rings a very familiar bell. Record types and their instances do look a lot like the classes and objects that you find in object-oriented languages. And protocols clearly resemble the abstract types or interfaces that you also find in the object-oriented world. None of this is by chance. Records are Clojure’s approach to building a structured, composite data type with predefined fields. Similarly, protocols are Clojure’s riff on type-based polymorphism—the idea that you can have a single operation implemented in different ways by different types.

But record types and values part company with object-oriented classes and objects ...