When working on my polymorphism presentation I learned that I did not have a firm grasp on records in clojure, which was effecting my ability to learn protocols.

What are records?

Records in Clojure are a type of data structure that allow you to define a blueprint for objects with named fields. They are similar to structs in other languages and provide a way to define a fixed schema for your data. Unlike maps, which can have any number of key-value pairs, records have a predefined set of fields.

Benefits of using records

  • Accessing fields in a record is generally faster than accessing keys in a map. This is because records are implemented as Java classes under teh hood, providing efficient field access.
  • Records enforce a fixed schema, which can help catch errors early by ensuring that only valid fields are accessed or modified.
  • Using records can make your code more readable and self-documenting by explicitly defining the structure of your data.

Using records

You can define records by using the defrecord macro.

(defrecord car [make model color])

To create an instance of a record you can use one of the records constructor functions (that clojure generates automatically under the hood when you define a record).

(def miata (->car "Mazda" "Miata" "Blue"))

(def miata (map->car {:make "Mazda" :model "Miata" :color "Blue"}))

Both do the same thing, but the ->"record-name" function is a little less verbose.

Any function that works with a map will also work with a record, although a few of the functions behave a little differently. dissoc will return a map, not another record. conj will also return a map when adding new key-value pairs.