iterate over PersistentVector of objects in clojure - arrays

Question

I am new to Clojure and I am trying to iterate over a PersistentVector of objects, which looks like below when I print in logs.
[{name John, email john#example.com} {name Peter, email peter#example.com}]
when I print (type myData) it tells me it is of type clojure.lang.PersistentVector
I have to iterate over this vector, extract email from each object inside it at a time and invoke another function.
It looks very simple, I looked at many samples and questions, but nothing seem to work for me :(
Thanks.

Answer 1

Here are a couple of options:
If you don't care about the objects ("maps" in Clojure speak) and only want to collect the emails and apply a function over them, you can create a simple function just to extract the emails into another collection and then use any function over the collection of emails:
(def items
[{"name" "John", "email" "john#example.com"} {"name" "Peter", "email" "peter#example.com"}])
(defn get-email [m]
(get m "email"))
(mapv get-email items)
;; returns: ["john#example.com", "peter#example.com"]
You can use function composition to the create a function that turns into upper case (using upper-case from clojure.string) the result of getting the email: (note the ordering in comp):
(mapv (comp clojure.string/upper-case get-email) items)
;; returns ["JOHN#EXAMPLE.COM" "PETER#EXAMPLE.COM"]
If you want to obtain a similar collection but with the email field updated, you can use update-in:
(mapv (fn [m] (update-in m ["email"] clojure.string/upper-case)) items)
;; Applies `upper-case` to the "email" path of each map identified by `m`.
;; returns: [{"name" "John", "email" "JOHN#EXAMPLE.COM"} {"name" "Peter", "email" "PETER#EXAMPLE.COM"}]
There are more elegant ways to do the same work using other techniques (anonymous functions, strs destructuring) but I think the ones above are simpler to understand if you are new to Clojure.