A string that uniquely identifies the match.
- iOS 5.0+
- macOS 10.8+
- tvOS 9.0+
- watchOS 3.0+
This string is not intended to be displayed to players. Your game should use this string whenever it needs to identify a specific match. For example, if you want your game to store additional information on a device or in iCloud, it might store it in a database using the match ID as a key.