Getting Clojure

Staying Out of Trouble

Possibly the biggest danger lurking inside of clojure.spec is related to mistyping a keyword while registering a spec. For example, if you do this you might think you are (among other things) declaring that the value associated with :title in a book map needs to be a string:

(s/def ::author string?)

(s/def ::titlo string?)

(s/def ::copies pos-int?)

(s/def ::book
       (s/keys :req-un [::title ::author ::copies]))

;; Register a spec for the find-by-title function.

(s/fdef find-by-title
  :args (s/cat :title ::title
               :inventory ::inventory))

But take a closer look and you will see that we misspelled ::title when defining the spec. This means that while books are required to have titles, since there is no ...