clojure Clojure destructuring Overview
Example
Destructuring allows you to extract data from various objects into distinct variables. In each example below, each variable is assigned to its own string (a="a", b="b", &c.)
| Type | Example | Value of data / comment |
|---|---|---|
vec | (let [[a b c] data ...) | ["a" "b" "c"] |
nested vec | (let [[[a b] [c d]] data ...) | [["a" "b"] ["c" "d"]] |
map | (let [{a :a b :b c :c} data ...) | {:a "a" :b "b" :c "c"} |
| — alternative: | (let [{:keys [a b c]} data ...) | When variables are named after the keys. |
Tips:
- Default values can be provided using
:or, otherwise the default isnil - Use
& restto store aseqof any extra values inrest, otherwise the extra values are ignored - A common and useful use of destructuring is for function parameters
- You can assign unwanted parts to a throw-away variable (conventionally:
_)
