Writing Game Center Apps in iOS

Displaying Leaderboards to Players

Problem

You want to display leaderboards to your app users using a graphical user interface.

Solution

Use the GKLeaderboardViewController class as shown in the Discussion section.

Discussion

Game Center can construct built-in leaderboard screens for your games. Doing this is a piece of cake for Game Center. All you have to do is build an iOS application that makes use of view controllers. This is outside the scope of this book, but is thoroughly explained in iOS 4 Programming Cookbook. For the remainder of this section, I assume you have created an application with one view controller inside a navigation controller.

To have Game Center construct a leaderboard screen for your iOS app, follow these steps:

1. Make sure that you have a view controller in your application (see iOS 4 Programming Cookbook). Also make sure that your view controller conforms to the GKLeaderboardViewControllerDelegate protocol.

2. Authenticate the local player (see Authenticating the Local Player in Game Center).

3. Allocate and instantiate an object of type GKLeaderboardViewController and present it to the player using the presentModalViewController:animated: instance method of your view controller.

4. Implement the leaderboardViewControllerDidFinish: delegate method of the GKLeaderboardViewControllerDelegate protocol in your view controller.

5. In the implementation of the leaderboardViewControllerDidFinish: delegate method, dismiss your leaderboard view controller using the view controller’s ...