Alexander Oloo

Alexander Oloo

Human. Engineer. Designer.

© 2019

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Fun with Clojure maps

There was a time where I was working exclusively in clojure and using SSR for the frontend. It was a peaceful time. But alas peace doesn’t last for ever. And then I picked up a new full stack project. A project building a SPA.

And JSON said to me: “Peace has cost you your strength. Victory has defeated you”.

The hastle of parsing json Node was all too fresh in my memory. Would Clojure be different?

(def json { :action "link-profiles", 
            :data { :user "alekcz", 
                    :social { :github "" 
                              :twitter ""}}})

The first time I had to parse a json request I hit a quick google. I was still quite new to Clojure so most problems involved a quick google. And voilà. Getting data from within a map"

So I tried get. And it was ridiculous

(get (get (get json :data) :social) :twitter)

And when something is unwieldy in Clojure there’s probably a more elegant way of doing it. You just need to be willing to look beyond the first google result.

(get-in json [:data :social :twitter])

Oh isn’t that nice. You gotta love the elegance. To be honest I thought that was as good as it got, until I stumbled across this gem. Turns out you can access data in a map using key like so:

(:data json)
; => {:user "alekcz", :social {:github "alekcz", :twitter "alekcz"}}

(:data nil) ; and doing this didn't crash anything.
; nil

It was like magic. Immediately it made me think of the thread-first macro. Maybe? Just maybe we could? Was it too good to be true? Surely not?

(-> json :data :social :twitter)
; => ""


May your build always pass.


This post is part of the “Advent of Parens”.