游戏中心领导委员会错误

我为游戏中心排行榜创build了这个代码，而且我总是得到Thread 1 signal Sigabrt 。 NSLOG总是这样说的：

 2014-04-15 15:27:28.441 GameCenter[38225:60b] -[GKGameCenterViewController setLeaderboardDelegate:]: unrecognized selector sent to instance 0xb48dd90 2014-04-15 15:27:28.442 GameCenter[38225:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[GKGameCenterViewController setLeaderboardDelegate:]: unrecognized selector sent to instance 0xb48dd90' *** First throw call stack: 

在我实现排行榜的代码截图下面：

或/请在这里看看这个问题： https : //stackoverflow.com/questions/23068184/game-center-leaderboard-doesnt-work-in-xcode