Would it be possible to create something like CL's multiple values this way?
2011/3/25 James Reeves <jree...@weavejester.com>: > On 25 March 2011 10:41, msappler <msapp...@web.de> wrote: >> Never used metadata until now. >> >> I had an insight yesterday that I want to share with you: >> >> http://resatori.com/metadata-insight > > In my view, it depends whether your :id key is a surrogate key or a natural > key. > > Object metadata should not affect object equality, so if your :id key > is just an internal database identifier, you could include it as > metadata. > > But if your :id key is exposed to the outside world, then it should > not be metadata, because changing the :id would change the external > representation of the object, and therefore affect equality. > > I should also point out that if you want information hiding, then > object composition might be a better solution. For example: > > (defprotocol Identifiable > (id [self] "Return an object's unique id")) > > (deftype DBRef [db-id data] > Identifiable > (id [_] db-id) > clojure.lang.IDeref > (deref [_] data)) > > (defn db-ref [id data] > (DBRef. id data)) > > Then we can get information about the reference, and deref it to get > its contents: > > (def user > (db-ref 193 {:login "fred"})) > > => (id user) > 193 > => @user > {:login fred} > > - 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 -- 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
