Clojurescript, how to access a map within a indexed sequence - data-structures

Question

(println (get-in #app-state ["my-seq"]))
Returns the following sequence with type cljs.core/IndexedSeq
([-Jg95JpA3_N3ejztiBBM {create_date 1421803605375,
website "www.example.com", first_name "one"}]
[-Jg95LjI7YWiWE233eK1 {create_date 1421803613191,
website "www.example.com", first_name "two"}]
[-Jg95MwOBXxOuHyMJDlI {create_date 1421803618124,
website "www.example.com", first_name "three"}])
How can I access the maps in the sequence by uid? For example, the map belonging to
-Jg95LjI7YWiWE233eK1

Answer 1

If you need the order of the data, you have the following possibilities:
Store the data once in order and once as a map. So, when adding a new entry, do something like:
(defn add-entry
[uid data]
(swap! app-state update-in ["my-seq"]
#(-> %
(update-in [:sorted] conj data)
(update-in [:by-uid] assoc uid data))))
With lookup functions being:
(defn sorted-entries
[]
(get-in #app-state ["my-seq" :sorted]))
(defn entry-by-uid
[uid]
(get-in #app-state ["my-seq" :by-uid uid]))
This has the best lookup performance but will use more memory and make the code a little bit more complex.
Search the entry in the seq:
(defn entry-by-uid
[uid]
(->> (get #app-state "my-seq")
(filter (comp #{uid} first))
(first)))
In the worst case, this has to traverse the whole seq to find your entry.
If order does not matter, I recommend storing the data as a map in the first place:
(defn add-entry
[uid data]
(swap! app-state assoc-in ["my-seq" uid] data))
(defn entry-by-uid
[uid]
(get-in #app-state ["my-seq" uid]))