APNS Device Token及didRegisterForRemoteNotificationsWithDeviceToken返回令牌的组成是什么？

Great question! Let's break down exactly what an APNS Device Token (including the one retrieved in the didRegisterForRemoteNotificationsWithDeviceToken method) consists of:

Core Basics #

First, at its root, an APNS Device Token is a 128-bit binary blob — when you see it in logs or send it to your server, it's almost always converted to a 32-character hexadecimal string (each hex character represents 4 bits of the original binary data).

Key Components #

While Apple doesn't publicly document the exact internal structure in full detail, we know it includes these critical elements:

• Device-specific identifier: A unique reference tied to the iOS/iPadOS device (but this isn't the old UDID, which is no longer allowed for developer use — it's an internal Apple-managed identifier for APNS).
• App Bundle ID binding: The token is explicitly linked to your app's Bundle ID, ensuring it can only be used to push notifications to your specific application on that device.
• Environment marker: A flag that distinguishes between the sandbox (development) and production APNS environments. Tokens generated in one environment won't work in the other.

Important Notes #

• Tokens aren't permanent! They can change if the user reinstalls your app, restores their device to factory settings, switches Apple IDs, or if Apple updates the APNS infrastructure. That's why you must always re-fetch the token on app launch and sync it with your server.
• It's not a device-wide unique ID — each app on the same device gets its own distinct APNS Device Token.

Example: Correctly Parsing the Token in Code #

Here's how to convert the raw Data object from didRegisterForRemoteNotificationsWithDeviceToken to the hex string you'll send to your server:

Swift

func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    let tokenString = deviceToken.map { String(format: "%02.2hhx", $0) }.joined()
    print("APNS Device Token: \(tokenString)")
    // Send tokenString to your backend server
}

Objective-C

- (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken {
    NSMutableString *tokenString = [NSMutableString string];
    const unsigned char *bytes = deviceToken.bytes;
    for (NSInteger i = 0; i < deviceToken.length; i++) {
        [tokenString appendFormat:@"%02x", bytes[i]];
    }
    NSLog(@"APNS Device Token: %@", tokenString);
    // Upload tokenString to your server
}

内容的提问来源于stack exchange，提问作者Akaanksha