Earned or Unearned Achievements
The easiest achievement from Table 4.1 to implement is the com.dragonforged.whackacac.killone achievement. Whenever you’re working with adding a hook for an achievement, the first step is to retrieve a copy of the GKAchievement that will be incremented. Use the method discussed in the section “Adding Achievement Hooks” to grab an up-to-date copy of the achievement.
GKAchievement *killOneAchievement = [[ICFGameCenterManager sharedManager] achievementForIdentifier: @"com.dragonforged.whackacac.killone"];
Next a query is performed to see whether this achievement has already been completed. If it has, there is no need to update it again.
if(
