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])")

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        }

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。

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。

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])")

斯威夫特5

func run() {
    let version = OperatingSystemVersion(majorVersion: 13, minorVersion: 0, patchVersion: 0)
    if ProcessInfo.processInfo.isOperatingSystemAtLeast(version) {
        runNewCode()
    } else {
        runLegacyCode()
    }
}

func runNewCode() {
    guard #available(iOS 13.0, *) else {
        fatalError()
    }
    // do new stuff
}

func runLegacyCode() {
    // do old stuff
}