如果你想查看WatchOS。

斯威夫特

let watchOSVersion = WKInterfaceDevice.currentDevice().systemVersion
print("WatchOS version: \(watchOSVersion)")

objective - c

NSString *watchOSVersion = [[WKInterfaceDevice currentDevice] systemVersion];
NSLog(@"WatchOS version: %@", watchOSVersion);

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        }

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
}

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。

细节

Xcode 10.2.1 (10E1001)

链接

OperatingSystemVersion

解决方案

extension OperatingSystemVersion {
    func getFullVersion(separator: String = ".") -> String {
        return "\(majorVersion)\(separator)\(minorVersion)\(separator)\(patchVersion)"
    }
}

let os = ProcessInfo().operatingSystemVersion
print(os.majorVersion)          // 12
print(os.minorVersion)          // 2
print(os.patchVersion)          // 0
print(os.getFullVersion())      // 12.2.0