ios - 根据设备 iOS 有条件地为 iOS 添加代码

Question

我想使用以下代码，但仅适用于在 iOS < 9 中运行的设备。特别是我想在装有 iOS8 的设备上运行它。

#if __IPHONE_OS_VERSION_MAX_ALLOWED < 90000

-(UIInterfaceOrientationMask)application:(UIApplication *)application supportedInterfaceOrientationsForWindow:(UIWindow *)window
{

    NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
    if(..)
      test()

    return UIInterfaceOrientationMaskPortrait | UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight;

}

#endif

但是，当我构建代码并在设备上运行它时，该方法并未执行。我做错了什么？该应用程序支持的最低 iOS 7.0 也可以在 iOS9 中运行(最新的 xcode 7)

Answer 1

使用这个“系统版本预处理器宏”检查系统版本

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)