Directives 101

We've now done some thinking and want to give our users an id instead of identifying them by email address. We're also a bit bored of seeing the same admin email address again and again.

Let's update our factory again:

(ns fab.tutorial
  (:require [fabrikk.alpha.core :as fab]))

(defn admin-email []
  (str "admin-" (rand-int 10000) "@example.com"))

(def user
  (fab/->factory
   ::user
   {:template {:id (fab/sequence)
               :name "John Smith"
               :email "[e-mail]"
               :role "user"
               :verified true}
    :traits {:admin {:email admin-email
                     :role "admin"}
             :unverified {:verified false}}}))

Now things are getting more interesting! We've introduced our first directives - special instructions to fabrikk.

The sequence directive provides an increasing series of integers. Perfect for giving each user a unique id:

(fab/build user)
;; => {:id 1, :name "John Smith", :email "[e-mail]", :role "user", :verified true}

(fab/build user)
;; => {:id 2, :name "John Smith", :email "[e-mail]", :role "user", :verified true}

I said directives plural above, so where's the other one? Well, technically, functions are directives too! When a template value is a zero argument function, fabrikk will invoke that function at build time and set the key to the return value.

(fab/build-list user 2 {:traits [:admin]})
;; => [{:id 3, :name "John Smith", :email "[e-mail]", :role "admin", :verified true}
;;     {:id 4, :name "John Smith", :email "[e-mail]", :role "admin", :verified true}]

Note that the admin-email function was specified in a trait, the following is true in general:

Anything that works for a template will work when specified in a trait.

Note that functions don't allow you to access the entity you're building, in the next section we'll cover another directive that lets you do that.