Im trying to calculate frame rate in cocoa. Is there a good function for getting the system time in cocoa?

Im just learning the Cocoa API's. Sorry if this is a stupid question.. since im sure the answer is silly obvious.

thx

You'll have to use the following Carbon function: CFAbsoluteTimeGetCurrent() (which returns a value in seconds).

You could also use [NSDate date] but I don't think that's a good decision.

+[NSDate timeIntervalSinceReferenceDate]

it returns a double, which is "seconds since 1970", but accurate to a few microseconds.

I do it like this sometimes:

[SOURCECODE]
- (void)setupRenderTimer
{
NSTimeInterval timeInterval = 0.01f;
renderTimer = [ [ NSTimer scheduledTimerWithTimeInterval:timeInterval target:self selector:@selector( animate ) userInfo:nil repeats:YES ] retain ];

[ [ NSRunLoop currentRunLoop ] addTimer:renderTimer forMode:NSEventTrackingRunLoopMode ];
[ [ NSRunLoop currentRunLoop ] addTimer:renderTimer forMode:NSModalPanelRunLoopMode ];

worldTime = [NSDate timeIntervalSinceReferenceDate];
}

- (void)animate
{
animate([NSDate timeIntervalSinceReferenceDate]-worldTime);
worldTime = [NSDate timeIntervalSinceReferenceDate];
}
[/SOURCECODE]

Thanks everyone.

I implemented it like this:
I store CFAbsoluteTime oldTime (as global data).

-(void) initGL:
oldTime = CFAbsoluteTimeGetCurrent();

- (void) drawRect: (NSRect)rect:
CFAbsoluteTime newTime = CFAbsoluteTimeGetCurrent();
double frameRate = 1.0/((double)newTime - (double)oldTime);
oldTime = newTime;
// then I print out the frameRate value to the screen

does this make sense?

Of course this is using the carbon libraries in a cocoa app. Hopefully apple wont depreciate carbon anytime soon. =)