swift3 - Swift 3 Result of call to (_:parameters:completionHandler:)' is unused warning and Braced block of statements is an unused closure error -

i have working swift.2.3 project when build , convert swift3 gives me:

result of call (_:parameters:completionhandler:)' unused warning. warning.

my clear working codes under below, how can convert them true way?

inmyclass;

     private func getmoviesdirectorsfromjson(jsondata: nsdata) throws -> [director] {             var directors = [director]()             {                 if let jsonobject = try nsjsonserialization.jsonobjectwithdata(jsondata, options: .allowfragments) as? [string: anyobject], jsonarray = jsonobject["actors"] as? [[string: anyobject]] {                     in jsonarray {                         var properties = [string: anyobject]()                         properties[directorjsonkeys.id] = i[directorjsonkeys.id]                         properties[directorjsonkeys.firstname] = i[directorjsonkeys.firstname]                         properties[directorjsonkeys.lastname] = i[directorjsonkeys.lastname]                         properties[directorjsonkeys.name] = i[directorjsonkeys.name]                         properties[directorjsonkeys.imageurl] = i[directorjsonkeys.imageurl]                         let director = director(properties: properties)                         directors.append(director)                     }                 }             } catch {                 throw myapperrors.parsingerror             }             return directors         }           public func directorshmovieswithmethod(method: string, parameters: string, completionhandler: (director: [director]?, error: errortype?) -> void) -> nsurlsessiontask! {             let session = nsurlsession.sharedsession()             guard let url = nsurl(string: parameters) else {                 completionhandler(director: nil, error: myapperrors.invalidurlerror)                 return nil             }             let request = nsurlrequest(url: url)              let task = session.datataskwithrequest(request) { data, response, error in                 if error != nil {                     completionhandler(director: nil, error: myapperrors.moviesearcherror)                 } else {                     {                         let director = try self.getmoviesdirectorsfromjson(data!)                         completionhandler(director: director, error: nil)                     } catch {                         completionhandler(director: nil, error: error)                     }                 }             }             task.resume()              return task         }      public func downloadimageatlocation(location: string, completionhandler: (imagedata: nsdata?, error: errortype?) -> void) -> nsurlsessiontask! {         let configuration = nsurlsessionconfiguration.defaultsessionconfiguration()         let session = nsurlsession(configuration: configuration)         guard let url = nsurl(string: location) else {             completionhandler(imagedata: nil, error: myapperrors.invalidurlerror)             return nil         }         let request = nsmutableurlrequest(url: url)         let task = session.datataskwithrequest(request) {data, response, error in             if error != nil {                 completionhandler(imagedata: nil, error: myapperrors.imagedownloaderror)             } else {                 completionhandler(imagedata: data, error: nil)             }         }         task.resume()          return task     } 

inmyview

        dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0)) {             myapp.sharedinstance().directorshmovieswithmethod("", parameters: myurl+"&dataformat=json") {directors, error in                 if error != nil {                     dispatch_async(dispatch_get_main_queue()) {                         self.showalert()                     }                 } else {                     dispatch_async(dispatch_get_main_queue()) {                         self.directors = directors!                         self.collectionview2.reloaddata()                      }                 }             } 

when using ;

 @discardableresult 

gives me error;

braced block of statements unused closure

you can annotate method warning @discardableresult.

for example:

@discardableresult func foobar() -> bool {     return true }