获取系统的当前版本并拆分它。 所以你可以得到大调和小调版本。

let sys_version = UIDevice.current.systemVersion
let all_version = sys_version.components(separatedBy: ".")
print("Major version : \(all_version[0])")
print("Minor version : \(all_version[1])")

快4.倍

func iOS_VERSION_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: NSString.CompareOptions.numeric) == ComparisonResult.orderedSame
}

func iOS_VERSION_GREATER_THAN(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: NSString.CompareOptions.numeric) == ComparisonResult.orderedDescending
}

func iOS_VERSION_GREATER_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: NSString.CompareOptions.numeric) != ComparisonResult.orderedAscending
}

func iOS_VERSION_LESS_THAN(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: NSString.CompareOptions.numeric) == ComparisonResult.orderedAscending
}

func iOS_VERSION_LESS_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: NSString.CompareOptions.numeric) != ComparisonResult.orderedDescending
}

用法:

if iOS_VERSION_GREATER_THAN_OR_EQUAL_TO(version: "11.0") {
    //Do something!
}

附:KVISH回答翻译成Swift 4。x和重命名函数，因为我专门为iOS应用程序使用这个片段。

马特·汤普森分享了一种非常简便的方法

switch UIDevice.currentDevice().systemVersion.compare("8.0.0", options: NSStringCompareOptions.NumericSearch) {
case .OrderedSame, .OrderedDescending:
    println("iOS >= 8.0")
case .OrderedAscending:
    println("iOS < 8.0")
}

如果你正在使用Swift 2，并且你想要检查操作系统版本以使用某个API，你可以使用新的可用性特性:

if #available(iOS 8, *) {
    //iOS 8+ code here.
}
else {
    //Code for iOS 7 and older versions.
    //An important note: if you use #availability, Xcode will also 
    //check that you don't use anything that was introduced in iOS 8+
    //inside this `else` block. So, if you try to use UIAlertController
    //here, for instance, it won't compile. And it's great.
}

我写这个答案是因为它是谷歌中swift 2 check系统版本查询的第一个问题。

我做了帮助函数，从下面的链接转移到swift:

我们如何通过程序检测设备运行的iOS版本?

func SYSTEM_VERSION_EQUAL_TO(version: String) -> Bool {
    return UIDevice.currentDevice().systemVersion.compare(version,
        options: NSStringCompareOptions.NumericSearch) == NSComparisonResult.OrderedSame
}

func SYSTEM_VERSION_GREATER_THAN(version: String) -> Bool {
    return UIDevice.currentDevice().systemVersion.compare(version,
        options: NSStringCompareOptions.NumericSearch) == NSComparisonResult.OrderedDescending
}

func SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.currentDevice().systemVersion.compare(version,
        options: NSStringCompareOptions.NumericSearch) != NSComparisonResult.OrderedAscending
}

func SYSTEM_VERSION_LESS_THAN(version: String) -> Bool {
    return UIDevice.currentDevice().systemVersion.compare(version,
        options: NSStringCompareOptions.NumericSearch) == NSComparisonResult.OrderedAscending
}

func SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.currentDevice().systemVersion.compare(version,
        options: NSStringCompareOptions.NumericSearch) != NSComparisonResult.OrderedDescending
}

它可以这样使用:

SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO("7.0")

斯威夫特4.2

func SYSTEM_VERSION_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: .numeric) == .orderedSame
}

func SYSTEM_VERSION_GREATER_THAN(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: .numeric) == .orderedDescending
}

func SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: .numeric) != .orderedAscending
}

func SYSTEM_VERSION_LESS_THAN(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: .numeric) == .orderedAscending
}

func SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(version: String) -> Bool {
    return UIDevice.current.systemVersion.compare(version, options: .numeric) != .orderedDescending
}

注:iOS 8.0及以上版本支持。OS X v10.10及以上版本

var majorVersion: Int    { return NSProcessInfo.processInfo().operatingSystemVersion.majorVersion }
var minorVersion: Int    { return NSProcessInfo.processInfo().operatingSystemVersion.minorVersion }
var patchVersion: Int    { return NSProcessInfo.processInfo().operatingSystemVersion.patchVersion }
var myOSVersion:  String { return NSProcessInfo.processInfo().operatingSystemVersionString        }