I know that lost feeling. I came from a background of OO too. Most of the
languages I'd used (C++, Java, Python, Go) had either total OO orientation,
or at least pushed you into an OO way of thinking. I found that reading
some Clojure books and other's code helped a lot (Joy of Clojure, Eric
Normand's content etc). Once I got my head around some practical examples
like the one you state, I found that my thinking changed. I also found the
MIT SCIP fried the way I think and spat it out anew. It takes time and
practice (well at least it took me time and practice).
I think that what you are doing is similar to something I did to get the
Google Identity Keys.
(defmethod ig/init-key ::get-google-keys [_ _]
(let [gkeys (ref {:keys nil :expires 0})]
(fn []
(let [current @gkeys]
(:keys (if (>= (c/to-epoch (t/now)) (:expires current))
(do
(log/info "Fetching Google Keys, expiry: " (:expires
current))
(dosync
(ref-set gkeys (fetch-google-keys ::jwk)))) ;; only use
JWK for now
current))))))
I was using the excellent Integrant library, but it would work the same
without it. I guess that you could do something similar with your token, if
it had expired, then it would fetch it?
The main thing that I changed in my mind is that it is ok to pass the state
to a function and get back a response, hiding everything in private data
doesn't give you as much as OO promises it will.
On Tuesday, 12 May 2020 09:38:08 UTC+1, Orestis Markou wrote:
>
> I’m interested in this too — you can get inspiration from
> https://github.com/cognitect-labs/aws-api/blob/master/src/cognitect/aws/credentials.clj
> which
> does something similar for expired credentials. Seems like a mutable
> internal field is fine for this use case.
>
> On 12 May 2020, at 9:27 AM, Scaramaccai <[email protected] <javascript:>>
> wrote:
>
> Hi everyone,
>
> I wanted to give a try to Clojure and functional programming in general
> but I can't really stop thinking "object oriented" or "with state
> everywhere". After 20+ years with objects + state I guess I'm lost without
> them :)
>
> The first thing I want to try is to get some data from an API that needs
> OAuth authentication. I would like to hide the fact that there's an OAuth
> token to be sent. In pseudo-Java I would do something like:
>
> class MyAuthHttpClient {
> private token;
> public MyAuthHttpClient(String usr, String psw) {...}
>
> public ... getResponse(Url) {
> // here check if token is available and if it is expiring;
> // if expiring -> fetch a new token before call the http service
> // caller doesn't even know there's a token involved in the process
> }
> }
>
> What's the proper way to do that in Clojure?
> I guess one way would be to have a function that returns a new token given
> a (possibly old) token and user+psw
>
> (defn gettkn [usr, psw, tkn] (return a new token if tkn is expiring or tkn if
> not expiring))
>
> (def wrap-gettkn (partial gettkn "myuser" "mypass"))
>
>
> (defn geturl [url, tkn] client/get url {:oauth-token (wrap-gettkn tkn)})
>
>
>
> I can "save" usr and psw, but I always have to "keep" the tkn around at
> every level;
> while I would like the token to be "hidden" to the "geturl" clients (just
> like I did in the "private token" in the pseudo-Java).
>
> What's the proper way of doing something like this in Clojure?
>
>
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