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

Answer 1

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!