Check if String contains substring in clojure

Question

I need to check if a java String contains a substring in my tests.

This doesn't work because java strings are not collections:

(deftest test_8
    (testing "get page from sputnik"
        (let [
            band "Isis"
            page (get-sputnikpage-for-artist band)
            ]
            (is (contains? band "Isis")))));does NOT work

Is there a way to convert java strings into collections? Or can I check for substring occurences in other ways?

Be aware that contains? does NOT check the existence of values, but existence of keys (maps) or indices (vectors and strings). One of the most common pitfalls in Clojure function naming. Both (contains? [1 2] 2) and (contains? "12" 2) => false because neither has an index 2 (only 0 & 1) — NielsK
– NielsK, Commented Oct 15, 2014 at 16:32

Diego Basch · Accepted Answer · 2014-10-15 16:00:38Z

78

The easiest way is to use the contains method from java.lang.String:

(.contains "The Band Named Isis" "Isis")

=> true

You can also do it with regular expressions, e.g.

(re-find #"Isis" "The Band Named Isis")

=> "Isis"

(re-find #"Osiris" "The Band Named Isis")

=> nil

If you need your result to be true or false, you can wrap it in boolean:

(boolean (re-find #"Osiris" "The Band Named Isis"))

=> false

edited Oct 15, 2014 at 16:00

answered Oct 15, 2014 at 15:54

Diego Basch

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Sanghyun Lee · Accepted Answer · 2016-03-21 02:53:00Z

65

Clojure 1.8 has introduced includes? function.

(use '[clojure.string :as s])
(s/includes? "abc" "ab") ; true
(s/includes? "abc" "cd") ; false

edited Mar 21, 2016 at 2:53

answered Jan 20, 2016 at 4:41

Sanghyun Lee

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Community · Accepted Answer · 2017-05-23 12:26:04Z

6

Strings are seqable:

(seq "Hello") ;;=> (\H \e \l \l \o)

... so you could use the sequence library to find a match:

(defn subsumes [main sub]
  (some
   (partial = (seq sub))
   (partition (count sub) 1 main)))

(subsumes "Hello" "ll") ;;=>> true

... but it's simpler and much faster to do as Diego Basch suggested.

edited May 23, 2017 at 12:26

CommunityBot

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answered Oct 15, 2014 at 17:29

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