I am new to clojure. I have a map fooBar :
#js {:foo 1, :bar 2}
I want to get foo. I have tried :
(:foo fooBar)
(get fooBar :foo)
The answer turned out to be simple field access :
(.-foo fooBar)
Related
I'm trying to create a state called items however my code gives an error and I'm unsure of why when I try to access the items and iterate over them. What am I doing wrong here?
(def items (r/atom ["test" "test2"]))
(defn home-page []
[:div#main
[:section.section
[:h1#s-one-greeting "Hello, I'm testing"]
[:h2#s-one-greeting-two "blah blah blah"]]
[:section.section
[:p "Work history"]
[:p "yada"]
[:p "yada"]
[:ul
(for [item items]
^{:key item} [:li "item " item])]]])
You are accessing items without derefing it. So you are trying to for loop over the reagent atom which doesn't work. Just switch it to (for [item #items] ...) and you should be fine.
I have my dependencies
(ns test.core
(:require [reagent.core :as reagent :refer [atom]]
[ajax.core :refer [GET]]))
I then have my handler that handles the responses to my ajax call
(defn handle-response [response]
(println (type response))
(println film))
THe data from my call is JSON, in the browser it looks like this:
{"id":3,"name":"Sicario","star":"Emily Blunt","rating":5}
When I run the above Clojure, I see this:
cljs.core/PersistentArrayMap core.cljs:192:23
{id 3, name Sicario, star Emily Blunt, rating 5}
Is their a way for me to go from the PersistArrayMap, and destructure it into id, name, star and rating?
I tried
(let [film (js->clj (.parse js/JSON response) :keywordize-keys true)]
...)
Hoping I would get a map named film, but no avail!
I think maybe I could use (get-in), but can't get the syntax right for this either.
Thanks,
Got it,
I was missing :response-format :json and :keywords? true from my GET call
Now, it looks like this:
(GET (str "https://localhost:5001/api/films/" film-name)
{:response-format :json
:keywords? true
And it all works.
I'm trying to pass a clojurescript map to a webworker.
Before I pass it, it is of type PersistentArrayMap.
cljs.core.PersistentArrayMap {meta: null, cnt: 3, arr: Array(6), __hash: null, cljs$lang$protocol_mask$partition0$: 16647951…}
However, when it gets to the worker, it's just a plain old Object
Object {meta: null, cnt: 3, arr: Array(6), __hash: null, cljs$lang$protocol_mask$partition0$: 16647951…}
with the data seemingly intact. At this point I'd like to turn it back into a PersistentArrayMap so that I can work with it in cljs again.
Using clj->js and js->clj doesn't really work because it doesn't distinguish between keywords and strings, so some data is lost.
What's the best way to handle this situation? It's possible that I'm going about this in the entirely wrong way.
The built-in solution is to serialize the data to EDN and reading it back. clj->js is inherently lossy and should be avoided.
You start by turning the object into a string and send that over to the worker.
(pr-str {:a 1})
;; => "{:a 1}"
In the worker you read it back via cljs.reader/read-string
(cljs.reader/read-string "{:a 1}")
;; => {:a 1}
This will usually be good enough but the transit-cljs library will be slightly faster. Depending on the amount of data you plan on sending it may be worth the extra dependency.
Did you use keywordize-keys in the code?
(def json "{\"foo\": 1, \"bar\": 2, \"baz\": [1,2,3]}")
(def a (.parse js/JSON json))
;;=> #js {:foo 1, :bar 2, :baz #js [1 2 3]}
(js->clj a)
;;=> {"foo" 1, "bar" 2, "baz" [1 2 3]}
(js->clj a :keywordize-keys true)
;;=> {:foo 1, :bar 2, :baz [1 2 3]}
Full documentation is here.
When defining a compojure handler e.g. by using the defroutes macro, I can do something like this:
(defroutes home-routes
(GET "/myhome/:id" [ id ] (home-page)))
(defn home-page [ id ]
( ... do something ... ))
So I know how to pass a piece of the path parameter. But imagine I want to return a HAL+JSON object with a selflink. How would I get defroutes to pass the whole URI to the home-page function?
The Ring request map contains all the necessary information to construct a "selflink". Specifically, :scheme, :server-name, :server-port, and :uri values can be assembled into full request URL. When I faced this problem I created Ring middleware that adds the assembled request URL to the Ring request map. I could then use the request URL in my handlers as long as I pass the request map (or some subset of it) into the handler. The following snippet shows one way of implementing this:
(defroutes app-routes
(GET "/myhome/:id" [id :as {:keys [self-link]}] (home-page id self-link))
(route/resources "/")
(route/not-found "Not Found"))
(defn wrap-request-add-self-link [handler]
(fn add-self-link [{:keys [scheme server-name server-port uri] :as r}]
(let [link (str (name scheme) "://" server-name ":" server-port uri)]
(handler (assoc r :self-link link)))))
(def app
(-> app-routes
handler/site
wrap-request-add-self-link))
I have a problem parsing json data in a loop. Iam a clojure beginner and need some hint for looping through json data.
The data looks like this:
{"photoset" {"primary" "8455893107", "total" "2", "pages" 1, "perpage" 500, "page" 1,
"per_page" 500, "photo"
[{"id" "8455893107", "secret" "1a3236df06", "server" "8087",
"farm" 9, "title" "IMG_0137", "isprimary" "1"}
{"id" "8469482476", "secret" "4c1bf59214",
"server" "8235", "farm" 9, "title" "HippieBus", "isprimary" "0"}]
, "owner"
"93029076#N07", "id" "72157632724688181", "ownername" "clojureB5"}, "stat" "ok"}
What I want to do is loop through the two photos and build a new url with the id and farm value like http://www.flickr.com/farm/id
I know that I can get one value like this:
(-> (get-in (cheshire.core/parse-string (:body picList)) ["photoset" "photo"]) first (get "id"))
But I can I now loop through it?
You can simply use map.
(->> (get-in data ["photoset" "photo"])
(map #(str "http://www.flickr.com/" (get % "farm") "/" (get % "id"))))
It will yield the following list:
("http://www.flickr.com/9/8455893107" "http://www.flickr.com/9/8469482476")