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。

2022年，Swift 5

extension Bundle {
    public var appName: String           { getInfo("CFBundleName")  }
    public var displayName: String       { getInfo("CFBundleDisplayName")}
    public var language: String          { getInfo("CFBundleDevelopmentRegion")}
    public var identifier: String        { getInfo("CFBundleIdentifier")}
    public var copyright: String         { getInfo("NSHumanReadableCopyright").replacingOccurrences(of: "\\\\n", with: "\n") }
    
    public var appBuild: String          { getInfo("CFBundleVersion") }
    public var appVersionLong: String    { getInfo("CFBundleShortVersionString") }
    //public var appVersionShort: String { getInfo("CFBundleShortVersion") }
    
    fileprivate func getInfo(_ str: String) -> String { infoDictionary?[str] as? String ?? "⚠️" }
}

用法(SwiftUI样本):

    Text("Ver: \(Bundle.main.appVersionLong) (\(Bundle.main.appBuild)) ")
    
    Text(Bundle.main.copyright)
        .font(.system(size: 10, weight: .thin))
        .multilineTextAlignment(.center)

奖励:版权支持\n符号!

我知道这个问题已经有人回答了，但我个人认为这个问题更清晰一些:

斯威夫特3.0:

 if let version = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String {
    self.labelVersion.text = version
}

斯威夫特< 2.3

if let version = NSBundle.mainBundle().infoDictionary?["CFBundleShortVersionString"] as? String {
    self.labelVersion.text = version
}

这样，if let版本就负责条件处理(在我的例子中设置标签文本)，如果infoDictionary或CFBundleShortVersionString为nil，则可选的展开将导致代码被跳过。

针对Swift 2.0

//First get the nsObject by defining as an optional anyObject

let nsObject: AnyObject? = NSBundle.mainBundle().infoDictionary!["CFBundleShortVersionString"]
let version = nsObject as! String

简单的实用函数返回应用程序版本为Int

func getAppVersion() -> Int {

        if let appVersion = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String {

            let appVersionClean = appVersion.replacingOccurrences(of: ".", with: "", options: NSString.CompareOptions.literal, range:nil)

            if let appVersionNum = Int(appVersionClean) {
                return appVersionNum
            }
        }
        return 0
    }

以下是Swift 3.2的更新版本:

extension UIApplication
{
    static var appVersion:String
    {
        if let appVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString")
        {
            return "\(appVersion)"
        }
        return ""
    }

    static var buildNumber:String
    {
        if let buildNum = Bundle.main.object(forInfoDictionaryKey: kCFBundleVersionKey as String)
        {
            return "\(buildNum)"
        }
        return ""
    }

    static var versionString:String
    {
        return "\(appVersion).\(buildNumber)"
    }
}