Hey, so I'm working with specter a bit, and one problem that I've noticed has come up several times which I feel has to have a normal solution, is that when I use transform there's no way to set the value if there is none already there. The solution I've had to use on several occasions is this:

(let [value (select-first [:path :to :val] structure)
      value (update-fn value)
      structure (setval [:path :to :val] value structure)]
  structure)

Everything else I've used in specter always feels like a great addition to Clojure, but this one hiccup is something that I've run into enough times that it almost makes me want to express this instead using a normal swap!

I'm a bit confused. This sort of thing (sp/transform [sp/ATOM key-path] update-fn db)) works just fine for me whether the final key exists or not. Also there is sp/BEGINNING and friends, which all work fine as well.

@suskeyhose ^^^^

Really? I'm not getting the function called at all with an example. Just a moment and I can give you the example that I'm running.

Yeah, works great - if it didn't, I would be hurting

Hmm. Well now it's working on the small example. Curious why it's not working in my larger code.

likely something else is happening

Further, yielding sp/NONE for the value removes the element (for example, k/v pair in a map) which is really wonderful

Yeah, I've used that a few times, which is fantastic

Okay, so the example in my code which this is working with is like this:

(transform [ATOM
            ::ds/rate-limits
            ::ds/endpoint-specific-rate-limits
            {::ds/action :create-message
             ::ds/major-variable {::ds/major-variable-type ::ds/channel-id
                                  ::ds/major-variable-value "286241942356885504"}}]
           #(println %)
           (atom #:discljord.specs{:rate-limits #:discljord.specs{:endpoint-specific-rate-limits {}}, :channel (a/chan 100), :token "TOKEN"}))

(transform [:key {:doesnt-exist :blah}] #(do (println %) :blah) {:key {}})

so apparently I can't use a map as a key and have it work

user> (select-first [{:blah :blah}] {{:blah :blah} :blah})
nil
user> (transform [{:blah :blah}] #(do (println %) :blah2) {{:blah :blah} :blah})
{{:blah :blah} :blah}

AFAIK using maps as paths doesn’t do anything

Yeah, that's the problem. I have need of using a map as a key, and if specter can't select or transform paths with maps, then I'm kind of screwed.

And just have to go back to traditional data manipulation

Well, you could try sp/map-key which maybe will work - but you are still not screwed. But you will need to create a custom navigator : https://github.com/nathanmarz/specter/wiki/Cheat-Sheet#custom-navigators

@suskeyhose ^^^

Okay, thanks. I'll take a look at it

@suskeyhose if you want to use a map as a key wrap it in keypath

oh, thanks!

keypath is the navigator that's implicitly used by keywords in paths

Ah, okay. Well that's exactly the behavior that I'd wanted, so that's exactly it. Thanks so much!

out of curiosity, is it possible to provide custom implicit navigators?

@schmee yes, through the ImplicitNav protocol

see https://github.com/nathanmarz/specter/blob/master/src/clj/com/rpl/specter.cljc#L1188