Programming Clojure, 2nd Edition

Datatypes

We have shown how to extend existing types to implement new abstractions with protocols, but what if we want to create a new type in Clojure? That is where datatypes come in.

A datatype provides the following:

• A unique class, either named or anonymous
• Structure, either explicitly as fields or implicitly as a closure
• Fields that can have type hints and can be primitive
• Optional implementations of abstract methods specified in protocols or interfaces
• Immutability on by default
• Unification with maps (via records)

We will use the deftype macro to define a new datatype, called CryptoVault, that will implement two protocols, including IOFactory.

Now that gulp and expectorate support several existing Java classes, let’s create a ...