Hey Jim -
The typical way that I like to handle this is with these methods from
NSRunLoop.h:
@interface NSObject (NSDelayedPerforming)
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument
afterDelay:(NSTimeInterval)delay inModes:(NSArray *)modes;
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument
afterDelay:(NSTimeInterval)delay;
+ (void)cancelPreviousPerformRequestsWithTarget:(id)aTarget selector:
(SEL)aSelector object:(id)anArgument;
#if MAC_OS_X_VERSION_10_2 <= MAC_OS_X_VERSION_MAX_ALLOWED
+ (void)cancelPreviousPerformRequestsWithTarget:(id)aTarget;
#endif
@end
When something about your object changes that means it needs to
recalculate its state in the future, I would note that the object has
become invalid, and then schedule a callback in the future to validate
the object. I would only schedule the call back if one wasn't already
scheduled. If I needed to validate the object state immediately, I
would cancel the callback and do immediate validation.
This is typically better than using a 0.5 second global timer because
it won't fire when it isn't in use. Also, is the value 0.5 really
special? You probably want to validate your objects at the end of the
current event loop. You can easily do this by passing a value of 0.0
into 'afterDelay:'. The semantics for a delay of 0.0 might mean at the
beginning of the next event loop, I'm not sure.
These after delay style messages can be easily abused and cause
confusion in your program logic, so use them wisely.
Jon Hess
On Aug 5, 2008, at 7:16 PM, Jim Crafton wrote:
Is there a way to handle idle time in an NSApplication? In Win32 or
Carbon, since you manually write the actual while loop that processes
the events, this is pretty easy to do. Is there anything like this in
Cocoa? I've got some objects whose state (possibly) needs to be
updated, and I was planning on handling this in the "idle" handler.
My other idea, if this is not possible, would be to simply have a
timer that fires off every 0.5 seconds or so.
Thanks
Jim C
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