Defining Multimethods

To define a multimethod, use defmulti:

 ​(​defmulti​ name dispatch-fn)​

name is the name of the new multimethod, and Clojure will invoke dispatch-fn against the method arguments to select one particular method (implementation) of the multimethod.

Consider my-print from the previous section. It takes a single argument, the thing to be printed, and you want to select a specific implementation based on the type of that argument. So, dispatch-fn needs to be a function of one argument that returns the type of that argument. Clojure has a built-in function matching this description, namely, class. Use class to create a multimethod called my-print:

 ​(​defmulti​ my-print class)​

At this point, ...

Get Programming Clojure, 2nd Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.