How to convert an APNs token to `String` from `Data`?

I think this is the best code to convert an APNs token to String from Data.

let token = deviceToken.map { String(format: "%.2hhx", $0) }.joined()

Usage

// Define initializer
extension String {
    public init(deviceToken: Data) {
        self = deviceToken.map { String(format: "%.2hhx", $0) }.joined()
    }
}

func application(_ application: UIApplication,
                 didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data!) {
    // Use like this:
    let token = String(deviceToken: deviceToken)
}

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Full Japanese version: Swiftでプッシュ通知用のDevice Token(Data型)を16進数文字列へ変換する方法 - Qiita