Thanks for the suggestions aditya. I definitely like where you are headed.
I have a few questions. This syntax in `pipeline-build-count` method looks
confusing to me:
> [{:keys [body] :as response}] ;; destructuring for convenience and
function API documentation
Would you mind breaking that down a little more?
Also, your program works great though it only returns a list of the latest
build numbers without the project name. I'm trying to think of how I could
include that but I'm not seeing it. The fetch pipeline response does
include the project name so I could just return it and the counter; so I
could return a tuple? or just two values (I think clojure can support
that). I'd rather just thread the project-name through though.
Thanks for all the help! I'm learning a ton.
On Monday, December 14, 2020 at 11:35:15 PM UTC-6 [email protected]
wrote:
> I'd try to separate the "I/O or side-effecting" parts from the "purely
> data processing" parts. This makes the program much easier to test --- the
> "purer" the code, the better it is. This also helps tease apart
> domain-agnostic parts from domain-specialised parts, which is useful,
> because domain-agnostic parts tend to be generalisable and thus more
> reusable.
>
> I'd also avoid mixing lazy functions like `map` with effectful things like
> `GET` requests, because :
> https://stuartsierra.com/2015/08/25/clojure-donts-lazy-effects
>
> I've taken the liberty to rearrange the code, and rename functions to
> illustrate what I mean.
>
> (defn pipeline-api-endpoint ;; lifted out of `fetch-pipeline`
> [project-name]
> ;; knows how to translate, or perhaps more generally, map, a project
> name to a project URL format
> (str "https://example.com/go/api/pipelines/"; project-name "/history"))
>
> (defn http-get-basic-auth ;; instead of `fetch-pipeline', because now
> this operation doesn't care about a specific type of URL
> [well-formed-url] ;; it can simply assume someone gives it a well-formed
> URL.
> (client/get well-formed-url
> {:basic-auth "username:password"})) ;; we'll see about this
> hard-coding later
>
> (defn pipeline-build-count ;; now this only cares about looking up build
> count, so no "GET" semantics
> ;; assumes it gets a well-formed response
> [{:keys [body] :as response}] ;; destructuring for convenience and
> function API documentation
> (-> body
> (parse-string true)
> :pipelines
> first
> :counter))
>
> (defn fetch-pipeline-counts! ;; ties all the pieces together
> [project-names]
> (reduce (fn [builds project-name]
> ;; uses reduce, not map, because:
> https://stuartsierra.com/2015/08/25/clojure-donts-lazy-effects
> (conj builds
> (-> project-name
> pipeline-api-endpoint
> http-get-basic-auth
> pipeline-build-count)))
> []
> project-names))
>
>
> Now... It turns out that fetch-pipeline-counts! is a giant effectful
> process, tied directly to http-get-basic-auth. We could try to lift out the
> effectful part, and try to make it a pure function.
>
> (defn http-get-basic-auth
> [well-formed-url username password]
> (client/get well-formed-url
> {:basic-auth (str username ":" password)}))
>
> (defn http-basic-auth-getter
> "Given basic auth credentials, return a function that takes an HTTP
> endpoint, and GETs data from there."
> [username password]
> (fn [well-formed-url]
> (http-get-basic-auth well-formed-url
> username
> password)))
>
> (defn fetch-pipeline-counts-alt
> [pipeline-fetcher project-names]
> ;; Easier to unit test. We can pass a mock fetcher that doesn't call
> over the network.
> ;; In fact, we can now use any kind of "fetcher", even read from a DB or
> file where we may have dumped raw GET results.
> (reduce (fn [builds project-name]
> (conj builds
> (-> project-name
> pipeline-api-endpoint
> pipeline-fetcher
> pipeline-build-count)))
> []
> project-names))
>
> (comment
> (fetch-pipeline-counts-alt (http-basic-auth-getter "username" "password")
> ["projectA"
> "projectB"
> "projectC"
> "projectD"])
> )
>
> A closer look might suggest that we're now describing processes that could
> be much more general than fetching pipeline counts from an HTTP endpoint...
>
> Enjoy Clojuring! :)
>
> On Monday, December 14, 2020 at 10:51:52 PM UTC+5:30 [email protected]
> wrote:
>
>> Very cool everyone. This is exactly the kind of feedback I was hoping
>> for. I'm going through Clojure for the Brave and I hadn't made it to the
>> macros chapter yet. That single threading macro is pretty sweet!
>>
>> Thanks everyone!
>>
>> On Monday, December 14, 2020 at 11:00:02 AM UTC-6 [email protected]
>> wrote:
>>
>>> Hey James,
>>>
>>> Another small suggestion is you can just pass println to map, since it
>>> takes 1 argument in your case.
>>>
>>> (map println (sort builds))
>>>
>>> But here, since you just want to perform side effects, maybe run! would
>>> be a better function to use.
>>>
>>> (run! println (sort builds))
>>>
>>> This would cause it to return just one nil. Clojure is a functional
>>> language, and every function returns a value. You'll see the return in
>>> your REPL, but if the program is run in another way, such as packaged as a
>>> jar, you would just see the print output.
>>>
>>> - Brandon
>>>
>>> On Mon, Dec 14, 2020 at 8:42 AM Justin Smith <[email protected]> wrote:
>>>
>>>> a small suggestion: you don't need to nest let inside let, a clause
>>>> can use previous clauses:
>>>>
>>>> (defn get-latest-build
>>>> [pipeline]
>>>> (let [response (fetch-pipeline pipeline)
>>>> json (parse-string (:body response) true)
>>>> [pipeline] (:pipelines json)]
>>>> (:counter pipeline))))
>>>>
>>>> also consider using get-in:
>>>>
>>>> (defn get-latest-build
>>>> [pipeline]
>>>> (let [response (fetch-pipeline pipeline)
>>>> json (parse-string (:body response) true)]
>>>> (get-in json [:pipelines 0 :counter])))
>>>>
>>>> finally, this can now be simplified into a single threading macro:
>>>>
>>>> (defn get-latest-build
>>>> [pipeline]
>>>> (-> (fetch-pipeline pipeline)
>>>> (:body)
>>>> (parse-string true)
>>>> (get-in [:pipelines 0 :counter])))
>>>>
>>>> On Mon, Dec 14, 2020 at 7:18 AM James Lorenzen <[email protected]>
>>>> wrote:
>>>> >
>>>> > Hello all,
>>>> > This is my first Clojure program and I was hoping to get some advice
>>>> on it since I don't know any experienced Clojure devs. I'm using it
>>>> locally
>>>> to print the latest build numbers for a list of projects.
>>>> >
>>>> > ```
>>>> > (ns jlorenzen.core
>>>> > (:gen-class)
>>>> > (:require [clj-http.client :as client])
>>>> > (:require [cheshire.core :refer :all]))
>>>> >
>>>> > (defn fetch-pipeline
>>>> > [pipeline]
>>>> > (client/get (str "https://example.com/go/api/pipelines/"; pipeline
>>>> "/history")
>>>> > {:basic-auth "username:password"}))
>>>> >
>>>> > (defn get-latest-build
>>>> > [pipeline]
>>>> > (let [response (fetch-pipeline pipeline)
>>>> > json (parse-string (:body response) true)]
>>>> > (let [[pipeline] (:pipelines json)]
>>>> > (:counter pipeline))))
>>>> >
>>>> > (def core-projects #{"projectA"
>>>> > "projectB"
>>>> > "projectC"
>>>> > "projectD"})
>>>> >
>>>> > (defn print-builds
>>>> > ([]
>>>> > (print-builds core-projects))
>>>> > ([projects]
>>>> > (let [builds (pmap #(str % " " (get-latest-build %)) projects)]
>>>> > (map #(println %) (sort builds)))))
>>>> > ```
>>>> >
>>>> > This will output the following:
>>>> > ```
>>>> > projectA 156
>>>> > projectB 205
>>>> > projectC 29
>>>> > projectD 123
>>>> > (nil nil nil nil)
>>>> > ```
>>>> >
>>>> > A few questions:
>>>> >
>>>> > How can this program be improved?
>>>> > How idiomatic is it?
>>>> > How can I prevent it from returning the nils at the end? I know this
>>>> is returning nil for each map'd item; I just don't know the best way to
>>>> prevent that.
>>>> >
>>>> > Thanks,
>>>> > James Lorenzen
>>>> >
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>>> To view this discussion on the web visit
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>>>
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