Schould I make my own c-in method here

[RoelofWobben]

My solution look then like this :

(defn my-update-in [m k f]
  (let [new_value (f (get m k))]
    (assoc m k new_value)))

good enough or is there more that I can do with my little knowlegde about clojure

[mvarela]

that looks more like an alternative to update. update-in would take a path, rather than a key. You can do a similar ting using assoc-in. The actual update-in is also variadic, but I guess you already know how to use apply for those cases.

[RoelofWobben]

??

I looked at the clojure page and found this examples

(def p {:name "James" :age 26})
;;=> #'user/p

(update-in p [:age] inc)
;;=> {:name "James", :age 27}

so what are you meaning with a path ?

[mvarela]

the point of update-in is that you can use it with nested maps:
(update-in {:a {:b 1}} [:a :b] inc) will yield {:a {:b 2}}.
If you try your approach, you’ll get a null pointer exception. (you’re using [:a] as the key, instead of a path to dig into.

[RoelofWobben]

hmm, then back to the drawing board I think.
Then I have to find a way to find the value of the right key and update that

so like this :

def m {:1 {:value 0, :active false}, :2 {:value 0, :active false}})

(update-in m [:1] assoc :value 1 :active true)
;;=>{:1 {:value 1, :active true}, :2 {:value 0, :active false}}

[RoelofWobben]

hmm, still doing something wrong here :

(defn my-update-in [m ks f args]
  (assoc m ks (apply f (get m ks) args)))

(my-update-in p [:1] :age inc)

; Execution error (IllegalArgumentException) at chapter5/my-update-in (form-init95645667318631163.clj:51).
; Don't know how to create ISeq from: clojure.core$inc

I can peek to the source but I rather do it without because otherwise I have to feeling I do not learn anything

[madbonkey]

Think about each step your update-in has to perform:

1. get the value at the given keypath
2. apply the function to that value (and other args)
3. set the value at the given keypath

The important piece of the ‚-in‘ variants of assoc/update is that they’re working with paths, not just 1 key, so step 1 and 3 are what you need to focus on