Clojure ns syntax cheat-sheet

ns-cheatsheet.clj

;;
;; NS CHEATSHEET
;;
;; * :require makes functions available with a namespace prefix
;;  and optionally can refer functions to the current ns.
;;
;; * :import refers Java classes to the current namespace.
;;
;; * :refer-clojure affects availability of built-in (clojure.core)
;;   functions.
;;
;; Updated: 12/09/2016 ~ghoseb

(ns foo.bar

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; Refers clojure.string into current NS, e.g.:
  ;;   (clojure.string/lower-case "FooBar)
  (:require [clojure.string])

  ;; Refers string into current NS, e.g.:
  ;;   (string/lower-case "FooBar")
  (:require [clojure.string :as string])

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; Refers all functions from clojure.string and
  ;; clojure.set into current NS, e.g.:
  ;;   (union #{:a :b} #{:a :c} #{:b :d})
  ;;   (lower-case "FooBar")
  (:require [clojure.string :refer :all]
            [clojure.set :refer :all])

  ;; Refers only lower-case and union into current NS, e.g.:
  ;;   (union #{:a :b} #{:a :c} #{:b :d})
  ;;   (lower-case "FooBar")
  (:require [clojure.string :refer [lower-case]]
            [clojure.set :refer [union]])

  ;; Refers ancestors & descendants into current NS as xml-ancestors & xml-descendants
  (:require clojure.data.zip)
  (:refer [clojure.data.zip :rename {ancestors xml-ancestors,
                                     descendants xml-descendants}])

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; Refers ArrayList and HashMap into current NS:
  (:import [java.util ArrayList HashMap])

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; Excludes built-in print
  (:refer-clojure :exclude [print])

  ;; Excludes all built-ins except print
  (:refer-clojure :only [print])

  ;; Renames built-in print to core-print
  (:refer-clojure :rename {print core-print})

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; Reload all dependencies while loading the ns
  (:require [clojure.string :as cs :refer [split join]] :reload)

  ;; Be verbose about loading the deps
  (:require [clojure.string :as cs :refer [split join]] :verbose)

  ;; There is also :reload-all that reloads every depenency in the ns
  (:require [clojure.string :refer [split join]] :reload-all)

  ;; Everything together
  (:require [clojure.string :as cs :refer [split join]] :verbose :reload))

What is the meaning of :refer in the following :
(:require [io.pedestal.service.http.route.definition :refer [defroutes]]

thanks!

Hmm. On "what means (:require [io.pedestal.service.http.route.definition :refer [defroutes]]) ", I got two hypotheses :

1. (:require [io.pedestal.service.http.route.definition])
   (:use [io.pedestal.service.http.route.definition :only [defroutes]])
2. (:use [io.pedestal.service.http.route.definition :only [defroutes]])

Don't know which would be right :/ if any ;)

I think I got it.

On the pedestal tutorial, http://pedestal.io/documentation/connecting-to-datomic/
I found :
(:require [datomic.api :as d :refer (q)]))

where we get access to every function by prefixing d/ in front of it. Except for the q function that we can access directly, thanks to :refer.

:)

I suggest adding the following as the combination of :only and :rename:

;; Refers sqrt into current NS as ccm-sqrt, other math functions are not
;; refered, e.g.
;; (ccm-sqrt 4)
[:use [clojure.contrib.math :only [sqrt] :rename {sqrt ccm-sqrt}]]

@cmpitg as far as I know :use is deprecated.

:refer lets you use the function without the namespace qualifier.

(ns wawa
(:require [datomic.api :as d :refer [q]]))

(= (d/q args) (q args) (datomic.api/q args) )

Awesome. I never get this right.

In my case, i need to set require with refering to some function, but already have that name bounded to another func(addevent). It's was too straightforward for me to be assume immediately.

(ns project.handler.addevent
    (:require 
        [project.view.pages :refer [addevent] :rename {addevent addevent-page}))

thanks bro greetings get to know