Alternative to `CACurrentMediaTime()` for scheduling events in SpriteKit - ios

Question

I'm relatively new to SpriteKit and am wondering what alternatives there are to using the CACurrentMediaTime() for scheduling events. For example, I may implement an algorithm that prevents a player from firing too many times by adding the last time they fired with some 'cool down' period, comparing it to the current media time:
BOOL canFire = self.lastFireInterval + self.coolPeriod < CACurrentMediaTime();
The problem I have run into is that if I decide to alter the speed of a node, or even the entire scene, this logic falls apart. For example, if I gave the player a speed-up power up, I could slow down all other nodes except for the player, but the timings would be messed up for enemies firing.
What other alternatives are there for CACurrentMediaTime() that factor in the speed of the node?

Answer 1

2 options come to mind regarding the timed to fire:
1) Create an ivar/property BOOL readyNextMove; for your player class. Then when your player shoots set the readyNextMove to false and add this code:
SKAction *wait = [SKAction waitForDuration:2.0];
SKAction *block0 = [SKAction runBlock:^{
readyNextMove = true;
}];
[self runAction:[SKAction sequence:#[wait, block0]]];
2) You can use the update:(CFTimeInterval)currentTime method to see how much time has elapsed from, for example you player shooting, and set readyNextMove accordingly.

Answer 2

It's a matter of taste. But for all games I keep an internal frame based clock which handles everything. I firmly believe this is the best way, but of course it depends on the scope of your project. This method is very rigid and guarantees continuity. If you use timers and your game lags, your continuity is thrown off (in some cases a shooter might shoot more times per frame than other parts of your game gets to move).
In aScene.h
long _currentTime = 0;
In aScene.m
-(void) update {
_currentTime++;
for(shooter * aShooter in self.shooters) {
[aShooter updateWithTime:_currentTime];
}
}
In your shooter.m
-(BOOL) tryShoot:(long)globalTime {
if(_lastShootingTime<globalTime-shootingCooldown) {
_lastShootingTime = globalTime;
[self fireBullet];
return YES;
}
return NO;
}
-(void) updateWithTime:(long)globalTime {
//...perform shooters action for that time frame
_lastUpdatedTime = globalTime;
}