Xcode 8, Swift 3:

let gAppVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") ?? "0"
let gAppBuild = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") ?? "0"

看过文档后，我认为以下内容更清晰:

let version = 
NSBundle.mainBundle().objectForInfoDictionaryKey("CFBundleShortVersionString") 
as? String

来源: 使用此方法优于其他访问方法，因为它在键可用时返回键的本地化值。

针对Swift 4.0

let version = Bundle.main.infoDictionary!["CFBundleShortVersionString"]!
let build = Bundle.main.infoDictionary!["CFBundleVersion"]!

Xcode 9.4.1 Swift 4.1

注意，使用localizedInfoDictionary来获取包显示名称的正确语言版本。

var displayName: String?
var version: String?
var build: String?

override func viewDidLoad() {
    super.viewDidLoad()

    // Get display name, version and build

    if let displayName = Bundle.main.localizedInfoDictionary?["CFBundleDisplayName"] as? String {
        self.displayName = displayName
    }
    if let version = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String {
        self.version = version
    }
    if let build = Bundle.main.infoDictionary?["CFBundleVersion"] as? String {
        self.build = build
    }
}

鉴于Swift一直在发展，我的回答(截至2015年8月):

let version = NSBundle.mainBundle().infoDictionary!["CFBundleVersion"] as! String

斯威夫特4

//首先通过定义一个可选的AnyObject来获取nsObject

let nsObject: AnyObject? = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as AnyObject

//然后将对象转换为String，但要小心，你可能需要再次检查是否为nil

let version = nsObject as! String