gamekit is a framework that provides leader board, achievements, and more features to an ios application. in this tutorial, we will be explaining the steps involved in adding a leader board and updating the score.

steps involved

step 1 − in itunes connect, ensure that you have a unique app id and when we create the application update with the bundle id and code signing in xcode with corresponding provisioning profile.

step 2 − create a new application and update application information. you can know more about this in apple-add new apps documentation.

step 3 − setup a leader board in manage game center of your application's page where add a single leaderboard and give leaderboard id and score type. here we give leader board id as tutorialspoint.

step 4 − the next steps are related to handling code and creating ui for our application.

step 5 − create a single view application and enter the bundle identifier is the identifier specified in itunes connect.

step 6 − update the viewcontroller.xib as shown below −

step 7 − select your project file, then select targets and then add gamekit.framework.

step 8 − create ibactions for the buttons we have added.

step 9 − update the viewcontroller.h file as follows −

#import <uikit/uikit.h>
#import <gamekit/gamekit.h>

@interface viewcontroller : uiviewcontroller
<gkleaderboardviewcontrollerdelegate>

-(ibaction)updatescore:(id)sender;
-(ibaction)showleaderboard:(id)sender;

@end

step 10 − update viewcontroller.m as follows −

#import "viewcontroller.h"

@interface viewcontroller ()
@end

@implementation viewcontroller

- (void)viewdidload {
   [super viewdidload];
   if([gklocalplayer localplayer].authenticated == no) {
      [[gklocalplayer localplayer] 
      authenticatewithcompletionhandler:^(nserror *error) {
         nslog(@"error%@",error);
      }];
   }    
}

- (void)didreceivememorywarning {
   [super didreceivememorywarning];
   // dispose of any resources that can be recreated.
}

- (void) updatescore: (int64_t) score 
   forleaderboardid: (nsstring*) category {
   gkscore *scoreobj = [[gkscore alloc]
   initwithcategory:category];
   scoreobj.value = score;
   scoreobj.context = 0;
   
   [scoreobj reportscorewithcompletionhandler:^(nserror *error) {
      // completion code can be added here
      uialertview *alert = [[uialertview alloc]
      initwithtitle:nil message:@"score updated succesfully" 
      delegate:self cancelbuttontitle:@"ok" otherbuttontitles: nil];
      [alert show];
   }];
}

-(ibaction)updatescore:(id)sender {
   [self updatescore:200 forleaderboardid:@"tutorialspoint"];
}

-(ibaction)showleaderboard:(id)sender {
   gkleaderboardviewcontroller *leaderboardviewcontroller =
   [[gkleaderboardviewcontroller alloc] init];
   leaderboardviewcontroller.leaderboarddelegate = self;
   [self presentmodalviewcontroller:
   leaderboardviewcontroller animated:yes];
}

#pragma mark - gamekit delegates
- (void)leaderboardviewcontrollerdidfinish:
(gkleaderboardviewcontroller *)viewcontroller {
   [self dismissmodalviewcontrolleranimated:yes];
}
@end

output

when we run the application, we'll get the following output −

when we click "show leader board", we would get a screen similar to the following −

when we click "update score", the score will be updated to our leader board and we will get an alert as shown below −