Swift: Generics & downcast to AnyObject -

i have following situation: (just copy playground)

import cocoa  protocol uid {     var uid: int {get set} }  class : uid {     var uid = 01 }  class manageuid<t: uid> {      let cache = nscache()      func adduid(aobj: t) {         cache.setobject(aobj, forkey:aobj.uid)     }      func deleteduid(aobj: t) {         cache.removeobjectforkey(aobj.uid)     } } 

this lead error "could not find overload setobject ..."

well know problem type of aobj in adduid, not clear compiler.

on way say

func adduid(aobj: t) {     cache.setobject(aobj a, forkey:aobj.uid) } 

but in case can skip generic topic completely. try downcast aobj anyobject or nsobject did not work.

any ideas?

i nice have generic version of cache :)

update:

on solution add @objc attribute on protocol, therefore protocol usable classes lead general restriction protocol. local solution in class manageuid.

i found solution, primary derived answer of question here: https://devforums.apple.com/thread/233432

 protocol uid {     var uid: int {get set}  }   @class_protocol  protocol objectuid : uid {   }    class manageuid<t: objectuid> {      let cache = nscache()      func adduid(aobj: t) {         cache.setobject(aobj, forkey:aobj.uid)     }      func deleteduid(aobj: t) {         cache.removeobjectforkey(aobj.uid)     }  }