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beginners 2025-06-25
vasilisk 2025-06-25T09:45:31.380729Z
how do experienced clojure dev validate a multi-arity constructor fn? Do you prefer the below? or do you spec them? or do you use assertions? or something else:
(defn octet-string
([]
(->OctetString (byte-array 0)))
([^bytes raw-value]
(when-not (bytes? raw-value)
(throw (IllegalArgumentException. "Expected byte array")))
(->OctetString (java.util.Arrays/copyOf raw-value (alength raw-value))))
([^bytes raw-value ^long offset ^long length]
(when-not (bytes? raw-value)
(throw (IllegalArgumentException. "Expected byte array")))
(when-not (and (int? offset) (>= offset 0))
(throw (IllegalArgumentException. "Offset must be a non-negative integer")))
(when-not (and (int? length) (>= length 0))
(throw (IllegalArgumentException. "Length must be a non-negative integer")))
(when (> (+ offset length) (alength raw-value))
(throw (IllegalArgumentException. "Offset + length exceeds array bounds")))
(->OctetString (java.util.Arrays/copyOfRange raw-value offset (+ offset length)))))
p-himik 2025-06-25T11:18:59.850459Z
In this case, I wouldn't validate anything since if something is wrong Arrays/copyOf itself or Clojure reflector would throw.
Sometimes I use :pre or assert when a clear message is useful, but only if the error is mostly for me or other developers working on the same project.
Specs/schemas - only when the error is for someone else, like e.g. when a public API is called. At that point, the schema is also made a part of the API description.
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