Best current version, without need to deal with numeric search within NSString is to define macros (See original answer: Check iPhone iOS Version)

Those macros do exist in github, see: https://github.com/carlj/CJAMacros/blob/master/CJAMacros/CJAMacros.h

Like this:

#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)

and use them like this:

if (SYSTEM_VERSION_LESS_THAN(@"5.0")) {    // code here}if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"6.0")) {    // code here}

Outdated version below

to get OS version:

[[UIDevice currentDevice] systemVersion]

returns string, which can be turned into int/float via

-[NSString floatValue]-[NSString intValue]

like this

Both values (floatValue, intValue) will be stripped due to its type, 5.0.1 will become 5.0 or 5 (float or int), for comparing precisely, you will have to separate it to array of INTs check accepted answer here: Check iPhone iOS Version

NSString *ver = [[UIDevice currentDevice] systemVersion];int ver_int = [ver intValue];float ver_float = [ver floatValue];

and compare like this

NSLog(@"System Version is %@",[[UIDevice currentDevice] systemVersion]);NSString *ver = [[UIDevice currentDevice] systemVersion];float ver_float = [ver floatValue];if (ver_float < 5.0) return false;

For Swift 4.0 syntax

below example is just checking if the device is of iOS11 or greater version.

let systemVersion = UIDevice.current.systemVersionif systemVersion.cgFloatValue >= 11.0 {    //"for ios 11"  }else{   //"ios below 11")  }

Update

From iOS 8 we can use the new isOperatingSystemAtLeastVersion method on NSProcessInfo

   NSOperatingSystemVersion ios8_0_1 = (NSOperatingSystemVersion){8, 0, 1};   if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion:ios8_0_1]) {      // iOS 8.0.1 and above logic   } else {      // iOS 8.0.0 and below logic   }

Beware that this will crash on iOS 7, as the API didn't exist prior to iOS 8. If you're supporting iOS 7 and below, you can safely perform the check with

if ([NSProcessInfo instancesRespondToSelector:@selector(isOperatingSystemAtLeastVersion:)]) {  // conditionally check for any version >= iOS 8 using 'isOperatingSystemAtLeastVersion'} else {  // we're on iOS 7 or below}

Original answer iOS < 8

For the sake of completeness, here's an alternative approach proposed by Apple itself in the iOS 7 UI Transition Guide, which involves checking the Foundation Framework version.

if (floor(NSFoundationVersionNumber) <= NSFoundationVersionNumber_iOS_6_1) {   // Load resources for iOS 6.1 or earlier} else {   // Load resources for iOS 7 or later}

I know I am too late to answer this question. I am not sure does my method still working on low iOS versions (< 5.0):

NSString *platform = [UIDevice currentDevice].model;NSLog(@"[UIDevice currentDevice].model: %@",platform);NSLog(@"[UIDevice currentDevice].description: %@",[UIDevice currentDevice].description);NSLog(@"[UIDevice currentDevice].localizedModel: %@",[UIDevice currentDevice].localizedModel);NSLog(@"[UIDevice currentDevice].name: %@",[UIDevice currentDevice].name);NSLog(@"[UIDevice currentDevice].systemVersion: %@",[UIDevice currentDevice].systemVersion);NSLog(@"[UIDevice currentDevice].systemName: %@",[UIDevice currentDevice].systemName);

You can get these results:

[UIDevice currentDevice].model: iPhone[UIDevice currentDevice].description: <UIDevice: 0x1cd75c70>[UIDevice currentDevice].localizedModel: iPhone[UIDevice currentDevice].name: Someones-iPhone002[UIDevice currentDevice].systemVersion: 6.1.3[UIDevice currentDevice].systemName: iPhone OS