swift - Cannot convert return expression type to return type with closure? -

hello have func pagination messages.

   class func listmessages() -> (int, int, ([chatitemprotocol]) -> void) {     let service = messageservice()     func list(count: int, offset: int, comp:([chatitemprotocol]) -> void) {         let params : [string : anyobject] = ["offset" : offset, "limit" : count]         service.listmessagesforroom(params) { (messages) in             comp(messages.map({$0}))         }     }     return list } 

and have error :

cannot convert return expression of type '(int, offset: int, comp: ([chatitemprotocol]) -> void) -> ()' return type '(int, int, ([chatitemprotocol]) -> void)' (aka '(int, int, array<chatitemprotocol> -> ())') 

listmessages(...) expects following tuple return type

(int, int, ([chatitemprotocol]) -> void) 

the function list(...), on other hand, uses above argument implicitly contain void (/empty tuple type ()) return type. i.e., full signature list(...) is

(int, int, ([chatitemprotocol]) -> void) -> () 

leading type mis-match when attempt return list return value of listmessages(...).

without knowing purpose of code, difficult give concrete advice, fix above modifying return type of listmessages(...) include () return type, in matching signature of list(...)

class func listmessages() -> ((int, int, ([chatitemprotocol]) -> void) -> ())