版本號判斷

Starting Xcode 9, in Objective-C:

if (@available(iOS 11, *)) {
    // iOS 11 (or newer) ObjC code
} else {
    // iOS 10 or older code
}

Starting Xcode 7, in Swift:

if #available(iOS 11, *) {
    // iOS 11 (or newer) Swift code
} else {
    // iOS 10 or older code
}

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 110000 // iOS 11

#else

#endif 


如果你是用10.3的SDK，那你就會看到下面的設定 （在10.3SDK中的AvailabilityInternal.h）

/* make sure a default max version is set */
    #ifndef __IPHONE_OS_VERSION_MAX_ALLOWED
        #define __IPHONE_OS_VERSION_MAX_ALLOWED     __IPHONE_10_3
    #endif

#define __IPHONE_2_0      20000
#define __IPHONE_2_1      20100
#define __IPHONE_2_2      20200
#define __IPHONE_3_0      30000
#define __IPHONE_3_1      30100
#define __IPHONE_3_2      30200
#define __IPHONE_4_0      40000
#define __IPHONE_4_1      40100
#define __IPHONE_4_2      40200
#define __IPHONE_4_3      40300
#define __IPHONE_5_0      50000
#define __IPHONE_5_1      50100
#define __IPHONE_6_0      60000
#define __IPHONE_6_1      60100
#define __IPHONE_7_0      70000
#define __IPHONE_7_1      70100
#define __IPHONE_8_0      80000
#define __IPHONE_8_1      80100
#define __IPHONE_8_2      80200
#define __IPHONE_8_3      80300
#define __IPHONE_8_4      80400
#define __IPHONE_9_0      90000
#define __IPHONE_9_1      90100
#define __IPHONE_9_2      90200
#define __IPHONE_9_3      90300
#define __IPHONE_10_0    100000
#define __IPHONE_10_1    100100
#define __IPHONE_10_2    100200
#define __IPHONE_10_3    100300
/* __IPHONE_NA is not defined to a value but is uses as a token by macros to indicate that the API is unavailable */