On 10 April 2011 22:24, Ken Wesson <kwess...@gmail.com> wrote: > On Sun, Apr 10, 2011 at 1:37 PM, James Reeves <jree...@weavejester.com> wrote: >> By adding error messages to predicates, we tightly couple the >> validation error with the predicate, which in general is considered >> bad. However, this might be a valid compromise, but only if it >> improves readability. > > I showed two posts ago how to keep that decoupled.
You decoupled the validation message (e.g. "age is required") from the validation error (e.g. :blank), but validation error is still tightly coupled to your predicate. Putting it another way, I can represent this code: (age-invalid-en (not-int-in-range? age 1 120)) With four separate predicates: (validate thing [:age present? "age is required"] [:age integer-string? "age must be a whole number"] [:age (at-least 1) "age must be at least 1] [:age (at-most 120) "nobody is that old"]) So your not-int-in-range? function is a compound function, made up of four simple functions. > I think it's a bit subtler than that. On the face, I wouldn't disagree > with that statement. But if you arrive at your security rules by two > different procedures, one resulting set of rules might specify > what-to-deny and be more secure than another that specifies > what-to-allow. That's possible, but is there anything that indicates the predicates I've used so far are less secure than the validation functions you've used? > And ultimately there's a mathematically equivalent > what-to-allow set for any what-to-deny set, and vice versa, like a > photograph and its negative. But if people are used to creating photographs, why change it around so they have to use the negative? - James -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
