ios 编译版本 最低版本 运行版本 动态链接库

if ([[UIDevice currentDevice].systemVersion floatValue] >= 10.0) 运行环境判断；

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0 编译器、开发环境支持；

部署环境支持；

UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter]

在低于库版本的运行环境运行时，center返回值为nil；

结论：

1）在对象或类符号不存在时，动态库没有任何存在，返回值为nil；

2）当一个类的接口存在跨系统级别的函数存在时，因为类或对象存在，函数符号不存在，所以存在崩溃的情况。

- (void)registerRemoteNotification {

if ([[UIDevice currentDevice].systemVersion floatValue] >= 10.0) {

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0 // Xcode 8编译会调用

UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];

center.delegate = self;

[center requestAuthorizationWithOptions:(UNAuthorizationOptionBadge | UNAuthorizationOptionSound | UNAuthorizationOptionAlert | UNAuthorizationOptionCarPlay) completionHandler:^(BOOL granted, NSError *_Nullable error) {

if (!error) {

NSLog(@"request authorization succeeded!");

}

}];

[[UIApplication sharedApplication] registerForRemoteNotifications];

#endif

} else if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {

UIUserNotificationType types = (UIUserNotificationTypeAlert | UIUserNotificationTypeSound | UIUserNotificationTypeBadge);

UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:types categories:nil];

[[UIApplication sharedApplication] registerUserNotificationSettings:settings];

[[UIApplication sharedApplication] registerForRemoteNotifications];

} else {

UIRemoteNotificationType apn_type = (UIRemoteNotificationType)(UIRemoteNotificationTypeAlert |

UIRemoteNotificationTypeSound |

UIRemoteNotificationTypeBadge);

[[UIApplication sharedApplication] registerForRemoteNotificationTypes:apn_type];

}

}