On 8 April 2011 23:21, Ken Wesson <kwess...@gmail.com> wrote: > Better yet: maybe we're looking at this backwards. Maybe what we want > isn't a predicate for *passed* validation, but a predicate for > *failed* validation: > > (defn s-blank? [x] > (if (empty? (.trim x)) "must not be blank"))
That particular example ties a predicate to a particular error message. Error messages should be independent of predicates, otherwise they can't be localized or changed to fit a specific situation. > This takes advantage of the fact that the error messages we want are > all "truthy". It's also the case that you often want to detect and > handle invalid input right away, then get to the meat of the logic. > The natural ordering of if, if-let, etc. puts the "true" case first. > Making the "true" case the error case lets you easily get it out of > the way first in your code. This would lead to a lot of validations with "not" in front of them. i.e not-email-address?, not-integer?, etc. - 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
