                                 }
                             }
                         default:
-                            completion(defaultRoundAvatarOfRadius(radius))
                             break
                         }
                     }


    func roundAvatarOfUser(user: User, withRadius radius: CGFloat, completion: (UIImage) -> ()) {

        // 为下面切换线程准备，Realm 不能跨线程访问
        let avatarURLString = user.avatarURLString
        let userID = user.userID

        if avatarURLString.isEmpty {
            completion(defaultRoundAvatarOfRadius(radius))
            return
        }



    func roundAvatarWithAvatarURLString(avatarURLString: String, withRadius radius: CGFloat, completion: (UIImage) -> ()) {

        completion(defaultRoundAvatarOfRadius(radius))

        if avatarURLString.isEmpty {
            return
        }

