User Agent Strings in Swift

UserAgent.swift

public class UserAgent {
    public static let userAgent: String? = {
        guard let info = Bundle.main.infoDictionary,
            let appNameRaw = info["CFBundleDisplayName"] ??  info[kCFBundleIdentifierKey as String],
            let appVersionRaw = info[kCFBundleVersionKey as String],
            let appName = appNameRaw as? String,
            let appVersion = appVersionRaw as? String
        else { return nil }

        #if canImport(UIKit)
        let scale: String
        if #available(iOS 4, *) {
            scale = String(format: "%0.2f", UIScreen.main.scale)
        } else {
            scale = "1.0"
        }

        let model = UIDevice.current.model
        let os = UIDevice.current.systemVersion
        let ua = "\(appName)/\(appVersion) (\(model); iOS \(os); Scale/\(scale))"
        #else
        let ua = "\(appName)/\(appVersion)"
        #endif

        return ua
    }()
}