Checking iOS Version

iOS 8 and later

Swift 3:

let minimumVersion = OperatingSystemVersion(majorVersion: 8, minorVersion: 1, patchVersion: 2)
if ProcessInfo().isOperatingSystemAtLeast(minimumVersion) {//current version is >= (8.1.2)} else {
    //current version is < (8.1.2)}

Swift 2.0 and later

if #available(iOS 9, *) {
  // iOS 9} else {
  // iOS 8 or earlier}

Compare versions

let minimumVersionString = "3.1.3"
let versionComparison = UIDevice.current.systemVersion.compare(minimumVersionString, options:
.numeric)
switch versionComparison {case .orderedSame, .orderedDescending:
        //current version is >= (3.1.3)
        breakcase .orderedAscending:
        //current version is < (3.1.3)
        fallthroughdefault:
        break;}

Objective-C

NSString *version = @"3.1.3";
NSString *currentVersion = @"3.1.1";
NSComparisonResult result = [currentVersion compare:version options:NSNumericSearch];
switch(result){case: NSOrderedAscending:
        //less than the current versionbreak;
  case: NSOrderedDescending:
  case: NSOrderedSame:// equal or greater than the current versionbreak; }

Device iOS Version

This will give current system version.

Objective-C

NSString *version = [[UIDevice currentDevice] systemVersion]

Swift

let version = UIDevice.currentDevice().systemVersion

Swift 3

let version = UIDevice.current.systemVersion