The user interface used to invite friends to a match or to allow Game Center to fill the remaining players needed for a match.
To show a matchmaking screen, initialize a new GKMatchmakerViewController object and set the delegate. Configure the view controller’s other properties to match your specific needs, then present the new view controller. and wait for the delegate to be called. The view controller’s delegate is notified when the matchmaking process is completed or canceled. In either situation, you dismiss the view controller. Listing 1 shows how to present the matchmaking user interface to the player.
If the user is creating the match, your game initializes the matchmaker view controller by creating a GKMatchRequest object that describes the desired match. This match request is passed to the init(matchRequest:) method. When this view controller is displayed, the local player can invite other players into the match.
If your game receives an invitation from another player, it receives a GKInvite object representing the match the player was invited to. You initialize the matchmaker view controller by passing the GKInvite object received from Game Kit to the init(invite:) method. When this view controller is presented to the player, the player joins the existing match, but is not allowed to invite others to the match.
On iOS, you present and dismiss the view controller from another view controller in your game, using the methods provided by the UIViewController class. In macOS, you use the GKDialogController class to present and dismiss the view controller.
A class implements the GKMatchmakerViewControllerDelegate protocol to receive notifications from a GKMatchmakerViewController object. The delegate is called if a new match has been successfully created, if the user cancels matchmaking, and if an error occurs. In all three cases, the delegate should dismiss the view controller.