login.swift

func loginUserWithUsername(username: String?, password: String?) throws -> String {
    guard let username = username where username.characters.count != 0 else {
        throw LoginError.EmptyUsername
    }
    
    guard let password = password where password.characters.count != 0 else {
        throw LoginError.EmptyPassword
    }
    ///Handle all the other,
    return "token:" + username
}