Hi, I have discovered strange difference between methods implemented directly in defrecord and methods added later using extend (extend-type).
I simplified the issue to code example listed bellow. Both records FooRec and BarRec implement simple protocol FooProto with method foo. There is also evil function transmogrify, which takes a function F and returns new function which calls F. I use transmogrify to produce function foo* If you call foo method directly, everything works as expected. When you call foo*, FooRec method is OK, but BarRec fails with following exception No implementation of method: :foo of protocol: #'user/FooProto found for class: user.BarRec Which looks weird because you can call foo directly... I expect that defrecord and extend use different approach to extending the type and foo* ends up with a reference to old version of protocol. `defrecord` somehow manages to modify directly the protocol definition referenced by foo*, while `extend` takes more immutable approach and replaces old protocol definition (which foo* cannot see). I briefly dived into Clojure sources and found that indeed `extend` ends with some sort of alter-root-var, while `defrecord` traces ends deep in java sources (deftype*). It would be good idea to unify defrecord and extend so they have same behaviour. Dan (defprotocol FooProto (foo [X Y] "Make a foo")) (defn transmogrify [F Y] (fn [A] (F A Y))) (def foo* (transmogrify foo "Bar")) (defrecord FooRec [] FooProto (foo [X Y] (println "Hello," Y))) (foo (FooRec.) "World") ; -> Hello, World (foo* (FooRec.)) ; -> Hello, Bar (defrecord BarRec []) (extend-type BarRec FooProto (foo [X Y] (println "Bar" Y))) (foo (BarRec.) "Bar") ; -> Bar Bar (foo* (BarRec.)) ; bang! ; No implementation of method: :foo of protocol: #'user/FooProto found for class: user.BarRec -- 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
