iOS 【iOS 8 中设置applicationIconBadgeNumber（app新消息数字标识）和消息推送】

摘要：在IOS7中设置applicationIconBadgeNumber不会有什么问题，但是直接在IOS8中设置applicationIconBadgeNumber会报错

因为在IOS8中要想设置applicationIconBadgeNumber，需要用户的授权，在IOS8中，需要加上下面的代码：

UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];
[[UIApplication sharedApplication] registerUserNotificationSettings:settings];

但是这两句如果是在IOS7的系统中运行的话就会报错，所以需要先判断IOS的版本，完整代码如下：

float version = [[[UIDevice currentDevice] systemVersion] floatValue];

if (version >= 8.0) {
UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];
[[UIApplication sharedApplication] registerUserNotificationSettings:settings];
}

如果是注册消息推送的话，需要这样写：

float version = [[[UIDevice currentDevice] systemVersion] floatValue];

if (version >= 8.0) {
UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];
[[UIApplication sharedApplication] registerUserNotificationSettings:settings];
[application registerForRemoteNotifications];
}