1.系统判断方法失效:

在你的项目中,当需要判断系统版本的话,不要使用下面的方法:
#define isiOS10 ([[[[UIDevice currentDevice] systemVersion]   substringToIndex:1] intValue]>=10)

它会永远返回NO,substringToIndex:1，在iOS 10 会被检测成 iOS 1了。
Objective-C:
#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)
或者使用:
if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion:(NSOperatingSystemVersion){ .majorVersion = 9, .minorVersion = 1, .patchVersion = 0}]) { 
    NSLog(@"Hello from > iOS 9.1");
}
if ([NSProcessInfo.processInfo isOperatingSystemAtLeastVersion:(NSOperatingSystemVersion){9,3,0}]) { 
    NSLog(@"Hello from > iOS 9.3");
}
也可以使用:
if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_9_0) { // do stuff for iOS 9 and newer} else { 
    // do stuff for older versions than iOS 9
}
有时候会缺少一些常量,NSFoundationVersionNumber是在NSObjCRuntime.h中定义的,作为Xcode7.3.1的一部分,我们设定常熟范围从iPhone OS 2到#define NSFoundationVersionNumber_iOS_8_4 1144.17,在iOS 10(Xcode 8)中,苹果补充了缺少的数字,设置有未来的版本.
#define NSFoundationVersionNumber_iOS_9_0 1240.1
#define NSFoundationVersionNumber_iOS_9_1 1241.14
#define NSFoundationVersionNumber_iOS_9_2 1242.12
#define NSFoundationVersionNumber_iOS_9_3 1242.12
#define NSFoundationVersionNumber_iOS_9_4 1280.25
#define NSFoundationVersionNumber_iOS_9_x_Max 1299

Swift:
if NSProcessInfo().isOperatingSystemAtLeastVersion(NSOperatingSystemVersion(majorVersion: 10, minorVersion: 0, patchVersion: 0)) { 
    // 代码块
}
或者:
if #available(iOS 10.0, *) {  
    // 代码块
} else { 
    // 代码块
}