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Transit

When marshalling data containing CLJS Bean types to Transit, special handlers must be specified when creating a Transit writer.

The CLJS Bean custom handlers are provided by calling cljs-bean.transit/writer-handlers, and are passed to Transit's writer constructor via the :handlers option. For example:

(require '[cognitect.transit :as t] 
         '[cljs-bean.core :refer [->clj]]
         '[cljs-bean.transit])

(defn roundtrip [x]
  (let [w (t/writer :json 
           {:handlers (cljs-bean.transit/writer-handlers)})
        r (t/reader :json)]
    (t/read r (t/write w x))))

With this set up, Transit marshalling will work properly.

For example (roundtrip (->clj #js {:a 1})) will produce the map {:a 1}.

Note that, on the receiving end, plain ClojureScript (not CLJS Bean) types are produced.

The custom handlers cover all of the CLJS Bean types. Examples:

  • (->clj #js {:a 1}) is a CLJS Bean map type, which becomes a persistent map when round tripping
  • (->clj #js [1 2]) is a CLJS Bean vector type, which becomes a persistent vector when round tripping
  • (seq (->clj #js {:a 1})) is a CLJS Bean sequence type, which which becomes a persistent list when round tripping
  • (rest (->clj #js [1 2])) is a CLJS Bean sequence type, which which becomes a persistent list when round tripping

With these handlers, nested types are properly supported. For example

(-> (->clj #js {:a 1
                :b #js [1 2]
                :c #js [1 2 3]})
 (update :c rest))

produces a bean, where the values under :b and :c are types specific to CLJS Bean

{:a 1, :b [1 2], :c (2 3)}

and if this value is passed to roundtrip, the result is a persistent map containing a persistent vector and persistent list.