How can I pretty print a PersistentHashMap in Clojure to a string?

Question

How can I pretty print a PersistentHashMap in Clojure to a string? I am looking for something like:

(str (pprint {... hash map here...})

which

Answer 1

(let [s (java.io.StringWriter.)]
  (binding [*out* s]
    (clojure.pprint/pprint {:a 10 :b 20}))
  (.toString s))

Edit: Equivalent succinct version:

(with-out-str (clojure.pprint/pprint {:a 10 :b 20}))

Answer 2

(pr-str {:a 1 :b 2}) ;; => "{:a 1, :b 2}"

Answer 3

This should help:

(clojure.pprint/write {:a 1 :b 2} :stream nil)

according to clojure.pprint/write documentation

Returns the string result if :stream is nil or nil otherwise.

Answer 4

user=> (import java.io.StringWriter)
java.io.StringWriter
user=> (use '[clojure.pprint :only (pprint)])
nil
user=> (defn hashmap-to-string [m] 
  (let [w (StringWriter.)] (pprint m w)(.toString w)))
#'user/hashmap-to-string
user=> (hashmap-to-string {:a 1 :b 2})
"{:a 1, :b 2}\n"