UIUserNotificationSettings settingsForTypes：使 iOS7 设备崩溃

Question

出于某种原因，每当我尝试在 iOS 7 设备上注册远程通知时，我的应用程序都会立即崩溃。我正在运行以下代码块：

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_8_0
    if ([[UIApplication sharedApplication] respondsToSelector:@selector(registerUserNotificationSettings:)]) {
        UIUserNotificationSettings* notificationSettings = [UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeAlert | UIUserNotificationTypeBadge | UIUserNotificationTypeSound) categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:notificationSettings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    } else {
        [[UIApplication sharedApplication] registerForRemoteNotificationTypes: (UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert)];
    }
#else
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes: (UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert)];
#endif

这应该允许我在 iOS 8 和 7 中顺利注册通知（正如我已经找到并查看的一些示例所建议的那样），但无论出于何种原因它仍然崩溃。我已将崩溃范围缩小到我发布的第三行代码——更具体地说是以下语句：[UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeAlert | UIUserNotificationTypeBadge | UIUserNotificationTypeSound) categories:nil]; 如果我将其设置为nil，则应用程序运行得非常好，但如果我将行留在其中开始崩溃。

我尝试在respondsToSelector if 语句中添加日志，但代码肯定没有在 iOS 7 设备上运行，所以我有点不知所措。

编辑： 经过几个小时的故障排除后，我终于设法找到了解决方法。我需要将 UIKit.framework 导入到 Linked Frameworks and Libraries 下的项目中，并将其设置为 optional。

Answer 1

我不知道#if，因为我从未使用过它们，但我有一个非常相似的代码正在运行，所以你可以试试这个：

if ([[UIApplication sharedApplication] respondsToSelector:@selector(registerUserNotificationSettings:)]) {
    // use registerUserNotificationSettings
    [[UIApplication sharedApplication] registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeSound | UIUserNotificationTypeAlert | UIUserNotificationTypeBadge) categories:nil]];

    [[UIApplication sharedApplication] registerForRemoteNotifications];

} else {
    // use registerForRemoteNotificationTypes:
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound)];
}

如果这对您不起作用，则可能是其他原因导致崩溃.. ninja-style..