On Thu, Oct 16, 2014 at 3:49 PM, James Reeves <ja...@booleanknot.com> wrote:
>
> {:name "Alice", :email "al...@example.com"}
>
> At this point, stop. You have your data model.
>
>
>
I think that coming from OO, the most disconcerting piece of Clojure's
philosophy is that it is relatively rare in Clojure to publish an API with
data accessors like `get-name`. The most common way to access the name
would be to simply use
(:name person)
But let's say later you decide you want your data model to be {:first-name
"Alice", :last-name "Beasley", :email "al...@example.com"}, and you want to
change name to be a computed value that concatenates first and last names
-- this is going to break all your existing code. If name were only
accessed throughout your code via the call `get-name`, then it would be
trivial to make this change.
(Theoretically, it is possible to implement a revision to a person data
structure by representing it as a custom map that reimplements keyword
access so that (:name person) calls a function rather than does the usual
keyword lookup, but I've never seen anyone do this, so I'm ignoring this
possibility for the purpose of this discussion).
Many OO languages force, or encourage you stylistically, to hide everything
behind setters and accessors, so you get for free the ability to change
your mind about the data model later.
With Clojure, it is very common to allow your data model to *be* the API.
This puts some additional pressure to get it right the first time. You
have to explicitly think ahead about which fields might need to change in
the future.
--Mark
P.S. To answer your specific questions about what is preferred, I'd go with
your version that looks like:
(defn make-customer [name email]
{:name name, :email email})
(def customer1 (make-customer "Tom" "em...@address.com"))
I wouldn't bother with records unless I needed to use protocols. I would
use a constructor like make-customer, but I would probably not use an
accessor like get-name. I think these would be the most common choices in
the Clojure community (although other choices are also valid).
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