//在cocos2d中,_cmd通常用于定时调用某个函数(schedule)
//比如下面方法利用_cmd能够不定时地调用某个函数
-(void) scheduleUpdates {
// schedule the first update as usual
[self scheduleselector(irregularUpdate interval:1];
}
-(void) irregularUpdateccTime)delta {
// unschedule the method first [self unschedule:_cmd];
// I assume you’d have some kind of logic other than random to determine
// the next time the method should be called
float nextUpdate = CCRANDOM_0_1() * 10;
// then re-schedule it with the new interval using _cmd as the selector
[self schedule:_cmd interval:nextUpdate];
}