定时消息 update:方法

scheduleUpdate方法会执行update:方法，每帧执行一次

或者指定定时方法

-(void) scheduleUpdates
{
[self schedule:@selector(updateTenTimesPerSecond:) interval:0.1f];
}
-(void) updateTenTimesPerSecond:(ccTime)delta
{
// this method is called according to its interval, ten times per second
} 

停止所有定时方法

[self unscheduleAllSelectors]; 

停止指定定时方法

[self unschedule:@selector(updateTenTimesPerSecond:)]; 

trick — 用_cmd关键字代替当前执行的方法，也就是current method

-(void) scheduleUpdates
{
[self schedule:@selector(tenMinutesElapsed:) interval:600];
}
-(void) tenMinutesElapsed:(ccTime)delta
{
// unschedule the current method by using the _cmd keyword
[self unschedule:_cmd];
} 

优先级

// in Node A
-(void) scheduleUpdates
{
[self scheduleUpdate];
}
// in Node B
-(void) scheduleUpdates
{
[self scheduleUpdateWithPriority:1];
}
// in Node C
-(void) scheduleUpdates
{
[self scheduleUpdateWithPriority:-1];
} 

ABC3个节点的优先级为C>A>B