Hello.guys. Anyone know a page break library for web?

Like for pagination for a server/client web app?

yes,clojure pagination lib

I have a question, I need print n time a string. for example. if i get the number 3, the string "example" should be print 3 times.

(fn[n]
  (println (repeat n (str "Example\n"))))

are you in a repl?

yes

can you evaluation (repeat 3 (str "Example\n"))

`(Example Example Example ) nil`

cool

so what does it mean to call println on a list

I dont need the list

well you made one

only need the string

correct

so we need to make a string rather than a list

but repeat always returns a seq of things

but we can apply str to stuff

(str "blah" "blah" "blah") "blahblahblah"

so, if we make a list of "Example", we can call string on that

:thinking_face:

(apply str (repeat 3 "blah")) "blahblahblah"

so, here we are using apply

if we called string on te list of (blah blah blah), it would "string" the structure

we want to call the function with that list as its arguments

which is apply versus standard function call

so we say hey, call the function str on with the arguments in this list

looks weird, but if we print that, we should get what we want

yes, it works.

thanks a lot.

there's another way to do it as well

and you can decide which way you prefer

ok, let me see..

https://clojuredocs.org/clojure.core/dotimes

rather than constructing what we want to print, we can take the traditional route and do what we want n number of times

so rather than making the string of three examples with line breaks, we could just "loop" and print example however many times we want

which you prefer probably largely depends on what else you're doing in your code

but probably always good to write things twice in two different styles while you are learning

yes, thanks. I get it.

Thanks for share with me the dotimes function.

no problem. happy coding!

yes !!!!!

This is the first time I have tried out playing with API's and I am trying to get some stuff from Meetup. I'm just stumped on the time format.

"id": "ngmmrlywjbdc",
"name": "Social Meetup",
"status": "upcoming",
"time": 1498118400000,
"updated": 1457950138000,
"utc_offset": 36000000,

@grounded_sage If you want to convert it to a normal time object. you can look at clj-time

I managed to find some information on it. Google didn't surface it very well with my queries but I got there in the end.

I'm looking to grab it on the front end so I guess I will have to find a cljs-time equivalent.

with that you can do (c/from-long (:time <naam variable))

@grounded_sage this is a timestamp, see https://en.wikipedia.org/wiki/Unix_time. And there is cljs-time: https://github.com/andrewmcveigh/cljs-time which is similar to clj-time

Also, please be aware that the map contains a "utc_offsett" which you would have to apply too, to get the correct time. Although it might be a bit difficult depending on the timezone the user consuming the API, sits.

Thank you. I think it's easier for now if I just manually update.

Hitting a lot of issues with Rum that are more critical

my homepage looks like this. The first page can be found with just / . Next pages are found with /pages=x . Must I make two seperate routes or can one route handle both cases

im trying to save an array of images to my postgres db.

im trying to save an array of images to my postgres db.

(doseq [file files]
                  (upload/save-image! user file))

@joakimmohn Not sure if I understand that correctly, but if you do get an exception, you should get rid of that first

in honeysql what is this operator ‘-> ‘ https://github.com/jkk/honeysql

-> (select :a :b :c)
    (from :foo)
    (where [:= :f.a "baz"]))

@sveri `(POST "/file" [] :multipart-params [files :- [TempFileUpload]] (doseq [file files] (db/save-image! "kappachino" file)) (ok))` This is how the handler looks like. I think the problem is that postgres isn't finished working before the next image is attempted to be stored.

If the images are small (< 50 kb it works fine)

@kevinbheda I'm pretty sure it's just a thread first macro http://clojuredocs.org/clojure.core/-%3E

@joakimmohn i am Sure that PostgreSQL Cab handle multiple parallel requests

Could you Post the exception please?

@sveri

i wrapped the operation in a try catch block and now i'm not able to recreate the problem, so i guess thats called a solution? should all db operations be wrapped in try catch blocks?

how do I compose futures together? Like if I want to map a function over a future is there a standard library function for that?

Ideally it would wait till the future is realized, then apply the function to that value, returning another future

your second comment makes me think that pmap might be what you're looking for

@adamkowalski

but though i can't think of something in clojure.core, using your description:

(defn chain [f] (fn [fut] (future (f @fut))))

(map (chain my-fn) my-seq-of-futures)

@joakimmohn If you wrap it in a try catch, the exception wont go away. You will just have to handle it explicitly then. What does your code look like now?

(POST "/file" []
                 :multipart-params [files :- [TempFileUpload]]
                 (doseq [file files]
                   (try
                     (upload/save-image! "userid" file)
                     (catch Exception e (.getNextException e))))
                 (ok))

in emacs clojure what is the short cut for copying s-expression ?

@joakimmohn Like this you catch the exception and thats about it. That is not the way to go. You should log at least and do something, depending on the exception. Instead of (.getNextException e) you could call (.printStackTrace e) to get an idea what it is about and post it here.

@sveri '(catch Exception e (.printStackTrace e))' I would post it here, but it seems like all the images are being stored without any issues now. I haven't used try/catch blocks a lot tbh

IM finisched reading compojure routes in detail. so if I make a routes like this ⁠⁠⁠⁠

 (GET "//?page=:page" [page] (home-page)) 

and a user uses only \ then page is nill

so I could make a test to look if page is nill with (let [page 1] (if (nil? page)))

so far , right ? @dpsutton

@roelofw you don't route on query params. In other words your route only has the URL in it

Also another gotcha will be that page will be a string when it comes from params so be aware of that.

oke, so the route is only \

the route is /

I will hit the page again to find out about url parameters

@roelof When reading, take the examples and implement them yourself

try them out

play around with it

I was following this example :

(GET "/user/:id" [id]
  (str "<h1>Hello user " id "</h1>"))  

Basically it goes like: 1. Make an assumption: If I change this, I expect that. 2. Test your assumption

where as far as I understand :id is a url parameter

or must I follow this example I found at stack overflow :

(GET "/:id/descendants" [id]
     :return [d/CategoryTreeElement]
     :path-params [id :- Long]
     :query-params [context-type :- d/ContextType
                    levels :- Integer
                    {tenant :- d/Tenant :DEF_TENANT}
                    {show-future :- Boolean false}
                    {show-expired :- Boolean false}
                    {show-suppressed :- Boolean false}
     :summary "Fetch category descendants"
     (ok ...))  

@roelofw that is an example of destructuring a parameter from the URI

you want an example of getting a query param

Stick to the compojure tutorial

oke, I think you mean this :

(GET "/:foo" [foo id]                    ; You can always destructure and use query parameter in the same way
  (str "Foo = " foo " / Id = " id))   
; curl get /bar?id=33 would be "Foo = bar / Id = 33"   

kind of but you don't need :foo in this example

that would pattern match this URL "/thisisfoo?id=1"

I know

🆒

oke, now I try to remember how to make optional parameters to a function

Multiple arity is what you need to google I think 🙂

I think I could do something like this (GET "/" [page 1 ]

Right. if im right this will take care that page is 1 if no value is given

or I have to use this trick : (defn foo [{:keys [a b c], :or {c 42}}]

where c is 42 when no value is given for c

Time for a break. My head is spinning right now

@dominicm thanks, I know I can use & s where s can have 0, 1 ,2 or more

but I do not see how I can make a default value when there are zero arguments

(defn defaulted ([x] (defaulted x default)) ([x y] ...))

(defn x
  ([] (x :default-value))
  ([param] (do-stuff-with-param))

or that, yeah

but in this case if you have one route that expects a page param you will never have zero args. You always have one....just it might be nil

(GET "/" [page] (hame-page page))

oke, then I have to check that in a let so I page has always a value

( if-let (nil? page) (=page 1)) I think

roelof a nice pattern for this is (defn find-page [p] (get {nil "/home" "/" "/home"} p p))

or map it to "1" or whatever

@agile_geek am I still on the right track ?

How do you work with unsigned longs in clojure?

and how would you convert one into a byte array

@roelofw yes although that if-let doesn't look right.

Here's a tip - if you want to return the value of a var if it's not nil and a default if it is, instead of if: (if page page "1") you can use or: (or page "1")

oh BTW (if page page "1") is the same as (if (not (nil? page)) page "1") as nil is falsey

@agile_geek so I can do (GET "/" [page] (home-page page))

and then this :

(defn home-page [page]
  (let [
        url ""
        options {:as :json :query-params {:key (env :key) :format "json" :type "schilderij" :toppieces "True" :p page }}]
    (or page "1")
    (layout/render
      "home.html" {:paintings (-> (client/get url options)
                                  api/read-numbers
                                  api/fetch-paintings-and-images-front-page)})))  

no that (or page "1") needs to set a variable in the let that you then reference in the options as the value of :p

oke, that would then be :

defn home-page [page]
  (let [ page  (or "page" 1 )
        url ""
        options {:as :json :query-params {:key (env :key) :format "json" :type "schilderij" :toppieces "True" :p page }}]
      (layout/render
      "home.html" {:paintings (-> (client/get url options)
                                  api/read-numbers
                                  api/fetch-paintings-and-images-front-page)})))  

Yes although I would avoid shadowing page just to avoid confusion:

(defn home-page [page]
  (let [ page-num (or page "1")
        url ""
        options {:as :json :query-params {:key (env :key) :format "json" :type "schilderij" :toppieces "True" :p page-num }}]
      (layout/render
      "home.html" {:paintings (-> (client/get url options)
                                  api/read-numbers
                                  api/fetch-paintings-and-images-front-page)})))  

and make sure your code is better formatted. Slack is not an IDE or an editor so hard to keep formatting consistent!

BTW can you see why (or page "1") will work? If not have a try of similar expressions in a repl

nice one

now testing the whole code again

Thanks for all the help

Tomorrow I try to make a pagination visible on the page

I have some ideas to make that work

oops, something is not right. when I do localhost:3000 I see this error message :

Wrong number of args (0) passed to: home/home-page  

roelof, just a heads up, you don't need to post every thing you are going to investigate

try to work on stuff on your own and come to us when you need help, but not just for every error that pops up

check your routes

Im busy with that

@roelofw I agree with @dpsutton. The way to learn is to try and investigate your problems, isolate as much of the problem as you can and create simple experiments to work out what's wrong. If you need to add println or debug. Distil the problem to a simple use case if possible and then you can easily communicate it to us without us having to understand your entire application. Having said all that, we don't mind helping but we want you to help yourself too

remember to use the repl as much as possible and read documentation and examples of functions

I want to +100 ☝️

I have made it work

Cool I would leave on a high note and carry on tomorrow

let your brain sleep on what you've learned

last question before I goto sleep : the right url for a page is now localhost:3000/?page=n

Yes

where n is an integer in the range 1 - 470

oke, then I have to look tomorrow why this is not working

when I change n I still see the same paintings

I think I have some logging to do for the urls

I think this can be a solution : https://github.com/nberger/ring-logger

Sleep for me now.

Thanks all again

every time I see someone leave the beginners channel I'm like "nice, another graduate..." 🙌:skin-tone-2: 🎓 🙌:skin-tone-2:

I think with me It will take a while before can leave this channel

I found this for logging

;; print request info to *out*:
(client/get "" {:debug true})

 

so I did

(defn home-page [page]
  (let [page-num (or "page" 1)
        url ""
        options {:as :json :query-params  {:key (env :key) :format "json" :type "schilderij" :toppieces "True" :p page-num :ps 10} }]
    (layout/render
      "home.html" {:paintings (-> (client/get url options {:debug true})
                                  api/read-numbers
                                  api/fetch-paintings-and-images-front-page)})))  

but no output to see on the console

What is out ?

in your repl, evaluate out

*out*

#object[java.io.PrintWriter 0x164cd27 "[email protected]"]

so I have to use print

but when I use print I still do not see the url and the request parameters so no luck

@roelof Please check the number of arguments client/get takes

I am not sure, but I suspect there should only be one options map

oke, when I try (print (client/get url options {:debug true } )) I see only the request back

I want to see the value of url options to see what url is send to the api

to see why I see the same paintings again no mather what the pagenumber is

@roelof Think carefully about the number of arguments you are passing to client/get there. You have options — isn’t :debug an option as well?

i’ve updated my cider nrepl version from 0.8.1 to 0.9 in my .lein/profiles.clj file. does this mean the next time i do lein deps, it’ll update automatically?