Issue on Xcode 8.1: : Cannot convert value of type '(Backendless User!) -> ()' to expected argument

General
1

Async method does not work.

2

backendless.userService.login(usernameField.text, password: passwordField.text,
response: { ( user : BackendlessUser!) -> () in
// print(“User has been logged in (ASYNC):”)
},
error: { ( fault : Fault!) -> () in
print(“Server reported an error: (fault)”)
}
)

3

i found the solution… change everything to optional value… change everthying to ?