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];

    }

}