Timer-Based Achievements
One of the most popular achievements in iOS gaming is to play for a certain amount of time. In Whack-a-Cac com.dragonforged.whackacac.play5Mins is used to track the user’s progress towards five minutes of total gameplay. This particular example exists for the loss-of-accuracy problem that was faced in the Whack 1000 example from earlier in this section, and it can be overcome in the same manner.
To track time, a NSTimer will be created. To determine how often the timer should fire, you will need to determine what 1% of five minutes is.
play5MinTimer = [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(play5MinTick) userInfo:nil repeats:YES];
When the timer fires a ...
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