= Keyword argument functions now also accept maps
Fogus
2021-03-18
:jbake-type: post

ifdef::env-github,env-browser[:outfilesuffix: .adoc]

To date, Clojure’s support for keyword arguments forces programmers to choose between creating APIs that better support people (accepting keyword args) or APIs that better support programs (by taking a map of those args).

Introduced in Clojure 1.11, a function specified to take keyword arguments may be passed a single map instead of or in addition to (and following) the key/value pairs. When a lone map is passed, it is used outright for destructuring, else a trailing map is added to the map built from the preceding key/values via `conj`. For example, a function that takes a sequence of optional keyword arguments and returns a vector containing the values is defined as:

[source,clojure]
----
(defn destr [& {:keys [a b] :as opts}]
  [a b opts])

(destr :a 1)
->[1 nil {:a 1}]

(destr {:a 1 :b 2})
->[1 2 {:a 1 :b 2}]
----

In Clojure 1.11 the call to `destr` accepts a mixture of key/value pairs and/or a lone (or trailing) map benefitting both programmer and program.

This enhancement is available now in `org.clojure/clojure "1.11.0-alpha1"`.
