if-let-all-each

gistfile1.clj

  
(defmacro if-let-all-each
  "Like if-let-all but allows for a return case in each binding & only has 1 body."
  [bindings & body]
  (let [pairs (partition 3 bindings)
        names (mapv first pairs)
        exprs (map second pairs)
        fail-vals (map #(nth % 2) pairs)
        exprs-in-if-let (fn self [[name1 & more-names] [expr1 & more-exprs] [val1 & more-vals]]
                          `(if-let [~name1 ~expr1]
                             ~(if more-names
                                (self more-names more-exprs more-vals))
                             ~val1))]
    (let [v (exprs-in-if-let names exprs fail-vals)]
       `(if (=  ~v nil)
         (do ~@body)
         ~v))))

;; Returns the failing clause's 3rd item (e.g. if thing1 is nil, returns "thing 1 was missing")
(if-let-all-each [thing1 (d/pull db '[*] id1) "thing 1 was missing"
                  thing2 (d/pull db '[*] id2) "thing 2 was missing"]
  ;; Now I can execute this body knowing thing1 and thing2 are both here
  )


;; Also tried:

                             (if ~more-names
                                ~(self more-names more-exprs more-vals)
                                 (do ~@body))

;; But that causes a stack overflow since ~(self ...) gets evaluated