ios注册远程推送通知

    ios8以后，ios远程推送的注册方式发生了变化：

ios8以前：

[[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound)];

ios8以后：

UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                             |UIRemoteNotificationTypeSound
                                                                                             |UIRemoteNotificationTypeAlert)
                                                                                 categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];

所以，ios8之后代码中要做区分处理：

if ([[UIApplication sharedApplication] respondsToSelector:@selector(isRegisteredForRemoteNotifications)]) {
        UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIRemoteNotificationTypeBadge
                                                                                             |UIRemoteNotificationTypeSound
                                                                                             |UIRemoteNotificationTypeAlert)
                                                                                 categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    } else {
        [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeBadge
                                                         |UIRemoteNotificationTypeSound
                                                         |UIRemoteNotificationTypeAlert)];
    }

否则，在ios8的系统上会出现问题。