[iphone] How can we programmatically detect which iOS version is device running on?

I want to check if the user is running the app on iOS less than 5.0 and display a label in the app.

How do I detect which iOS is running on user's device programmatically?

Thanks!

Marek Sebera's is great most of the time, but if you're like me and find that you need to check the iOS version frequently, you don't want to constantly run a macro in memory because you'll experience a very slight slowdown, especially on older devices.

Instead, you want to compute the iOS version as a float once and store it somewhere. In my case, I have a GlobalVariables singleton class that I use to check the iOS version in my code using code like this:

if ([GlobalVariables sharedVariables].iOSVersion >= 6.0f) {
    // do something if iOS is 6.0 or greater
}

To enable this functionality in your app, use this code (for iOS 5+ using ARC):

GlobalVariables.h:

@interface GlobalVariables : NSObject

@property (nonatomic) CGFloat iOSVersion;

    + (GlobalVariables *)sharedVariables;

@end

GlobalVariables.m:

@implementation GlobalVariables

@synthesize iOSVersion;

+ (GlobalVariables *)sharedVariables {
    // set up the global variables as a static object
    static GlobalVariables *globalVariables = nil;
    // check if global variables exist
    if (globalVariables == nil) {
        // if no, create the global variables class
        globalVariables = [[GlobalVariables alloc] init];
        // get system version
        NSString *systemVersion = [[UIDevice currentDevice] systemVersion];
        // separate system version by periods
        NSArray *systemVersionComponents = [systemVersion componentsSeparatedByString:@"."];
        // set ios version
        globalVariables.iOSVersion = [[NSString stringWithFormat:@"%01d.%02d%02d", \
                                       systemVersionComponents.count < 1 ? 0 : \
                                       [[systemVersionComponents objectAtIndex:0] integerValue], \
                                       systemVersionComponents.count < 2 ? 0 : \
                                       [[systemVersionComponents objectAtIndex:1] integerValue], \
                                       systemVersionComponents.count < 3 ? 0 : \
                                       [[systemVersionComponents objectAtIndex:2] integerValue] \
                                       ] floatValue];
    }
    // return singleton instance
    return globalVariables;
}

@end

Now you're able to easily check the iOS version without running macros constantly. Note in particular how I converted the [[UIDevice currentDevice] systemVersion] NSString to a CGFloat that is constantly accessible without using any of the improper methods many have already pointed out on this page. My approach assumes the version string is in the format n.nn.nn (allowing for later bits to be missing) and works for iOS5+. In testing, this approach runs much faster than constantly running the macro.

Hope this helps anyone experiencing the issue I had!

[[[UIDevice currentDevice] systemVersion] floatValue]

In MonoTouch:

To get the Major version use:

UIDevice.CurrentDevice.SystemVersion.Split('.')[0]

For minor version use:

UIDevice.CurrentDevice.SystemVersion.Split('.')[1]

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
}

To get more specific version number information with major and minor versions separated:

NSString* versionString = [UIDevice currentDevice].systemVersion;
NSArray* vN = [versionString componentsSeparatedByString:@"."];

The array vN will contain the major and minor versions as strings, but if you want to do comparisons, version numbers should be stored as numbers (ints). You can add this code to store them in the C-array* versionNumbers:

int versionNumbers[vN.count];
for (int i = 0; i < sizeof(versionNumbers)/sizeof(versionNumbers[0]); i++)
    versionNumbers[i] = [[vN objectAtIndex:i] integerValue];

* C-arrays used here for more concise syntax.

[[UIDevice currentDevice] systemVersion]

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

A simple check for iOS version less than 5 (all versions):

if([[[UIDevice currentDevice] systemVersion] integerValue] < 5){
        // do something
};

[[UIDevice currentDevice] systemVersion];

or check the version like

You can get the below Macros from here.

if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(IOS_VERSION_3_2_0))      
{

        UIImageView *background = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"cs_lines_back.png"]] autorelease];
        theTableView.backgroundView = background;

}

Hope this helps