Safe way to get current app version and build

AppVersion.swift

import Foundation

struct AppVersion {
    static func version() -> String? {
        return NSBundle.mainBundle().infoDictionary?["CFBundleShortVersionString"] as? String
    }

    static func build() -> String? {
        return NSBundle.mainBundle().infoDictionary?["CFBundleVersion"] as? String
    }

    static func fullVersionString() -> String? {
        guard let version = version() else { return nil }
        guard let build = build() else { return version }
        return "\(version) (\(build))"
    }
}