clojure.edn/read-string

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Type: function Added: Clojure 1.5 Examples: 4 Runnable: 0

([s] [opts s])

Reads one object from the string s. Returns nil when s is nil or empty.

Reads data in the edn format (subset of Clojure data): http://edn-format.org

opts is a map as per clojure.edn/read

Examples

by phreed on 2014-10-02 . May have evaluation errors. ▶

;; The following code is a subset of that found at ;; http://www.compoundtheory.com/clojure-edn-walkthrough ;; It illustrates the fact that the readers ;; 'read' and 'read-string' have symmetric writers ;; 'prn' and 'prn-str'. (ns edn-example.core (require [clojure.edn :as edn])) (def sample-map {:foo "bar" :bar "foo"}) ;; Here you can see that the 'prn-str' is the writer... (defn convert-sample-map-to-edn "Converting a Map to EDN" [] ;; yep, converting a map to EDN is that simple" (prn-str sample-map)) (println "Let's convert a map to EDN: " (convert-sample-map-to-edn)) ;=> Let's convert a map to EDN: {:foo "bar", :bar "foo"} ;; ...and the reader is 'read-string' (println "Now let's covert the map back: " (edn/read-string (convert-sample-map-to-edn))) ;=> Now let's covert the map back: {:foo bar, :bar foo}

by humorless on 2017-09-06 . May have evaluation errors. ▶

;; The following demonstrates the use case of edn built-in tagged elements (class (clojure.edn/read-string "#inst \"1985-04-12T23:20:50.52Z\"")) java.util.Date

by Atsman on 2017-11-12 . May have evaluation errors. ▶

;; if you want to specify custom processing of some field add tag and function which process it ;; let's assume we have edn with some relative paths and want to make them absolute (def config "{:k8s-path #path \"./infra/k8s\"}") (defn absolute [path] "/users/some_user/project/k8s-path") (edn/read-string {:readers {'path absolute}} config) {:k8s-path "/users/some_user/project/k8s-path"}

by manojarya on 2019-09-25 . May have evaluation errors. ▶

;; following example adds a custom data-reader which dynamically resolves value ;; of a property from a lookup map. Falls back on default value if specified. (defn lookup-reader [lookup-map] (fn [v] (let [[k default-value] (if (sequential? v) v [v nil])] (get lookup-map k default-value)))) ;; returns readers map of tag symbols and handler functions (defn readers [lookup-map] {:readers {'prop (lookup-reader lookup-map)}}) ;; DB_HOST value is resolved while DB_PORT will be default (edn/read-string (readers {"DB_HOST" "db-server1"}) "{:host #prop [\"DB_HOST\" \"localhost\"] :port #prop [\"DB_PORT\" 42]}") ;; {:host "db-server1", :port 42}

See also

• clojure.edn/read (2)
• clojure.core/prn-str (2)
• clojure.core/read-string (4)
• clojure.main/load-script
• clojure.core/tagged-literal (0)

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