gistfile1.txt

(defmacro write-builder [cube & ats]
  `(loop [builder# (WriteBuilder. ~cube)
          ats# ~@ats]
     (cond
      (empty? ats#) builder#
      :else (do
              (recur (.at builder# (first ats#)) (rest ats#))))))



(write-builder cube [[time (now)]])


results in

xi:datablock (1) $ lein run
Exception in thread "main" java.lang.IllegalArgumentException: No matching method found: at for class com.urbanairship.datacube.WriteBuilder
        at clojure.lang.Reflector.invokeMatchingMethod(Reflector.java:53)
        at clojure.lang.Reflector.invokeInstanceMethod(Reflector.java:28)
        at datablock.core$_main.doInvoke(core.clj:58)
        at clojure.lang.RestFn.invoke(RestFn.java:397)
        at clojure.lang.Var.invoke(Var.java:411)
        at user$eval619.invoke(NO_SOURCE_FILE:1)
        at clojure.lang.Compiler.eval(Compiler.java:6511)
        at clojure.lang.Compiler.eval(Compiler.java:6501)
        at clojure.lang.Compiler.eval(Compiler.java:6477)
        at clojure.core$eval.invoke(core.clj:2797)
        at clojure.main$eval_opt.invoke(main.clj:297)
        at clojure.main$initialize.invoke(main.clj:316)
        at clojure.main$null_opt.invoke(main.clj:349)
        at clojure.main$main.doInvoke(main.clj:427)
        at clojure.lang.RestFn.invoke(RestFn.java:421)
        at clojure.lang.Var.invoke(Var.java:419)
        at clojure.lang.AFn.applyToHelper(AFn.java:163)
        at clojure.lang.Var.applyTo(Var.java:532)
        at clojure.main.main(main.java:37)
xi:datablock (1) $ 

The WriteBuilder class does have an at method.

https://github.com/urbanairship/datacube/blob/master/src/main/java/com/urbanairship/datacube/WriteBuilder.java