Re: Using asynchronous clojure function

[Brandon R]

Hi Ganesh,

The function called wrap-content-type takes in another function (handler) and a content-type (string), and returns a function. The function that it returns takes in a request, which is a Clojure map, that has the keys that you see in the ring docs here: https://github.com/ring-clojure/ring/wiki/Concepts#requests

That function that is returned, that takes in a request, is known as middleware. It calls the handler passed into wrap-content-type, which is another handler function (returns a ring response), then attaches the content type passed into wrap-content-type to the headers of the ring response. So the response might then look like {:headers {"Content-Type": "application/json"}} (if "application/json" was passed as content-type), along with whatever other keys/values were on the response before it was passed into the function.

FYI, the #beginners channel of the Clojurians Slack is super helpful for general questions like this.

Happy coding,

Brandon

On Sun, Dec 13, 2020 at 7:08 AM Ganesh Neelekani <ganeshn...@gmail.com> wrote:

Hello Team,

I am a moderate Clojure user and now I planned to explore more Clojure, I used to 

write different functions every time where I could write asynchronous functions. 

As came from object-oriented background and trying to understand asynchronous functions

I took some example on using fn functions

((fn [& nums] (/ (apply + nums) (count nums))) 1 2 3 4)

In the above statement, 1 2 3 4 is added after the function defined as input,

But in the below function I did not understand how fn behaves, what is the input for a request, Or what is the methodology , Basically I am not understanding the flow,

(defn wrap-content-type [handler content-type] 

     (fn [request] 

           (let [response (handler request)] 

                (assoc-in response [:headers "Content-Type"] content-type))))

Can someone help me, please?

Thanks,

Ganesh N

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