macOS ull?

[MrFusion]

dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 3ull*NSEC_PER_SEC, 500ull);

Anyone know what "ull" stands for? Thanks.

 

[Catfish_Man]

unsigned long long. It's making the size of the constant explicit.

 

[MrFusion]

unsigned long long. It's making the size of the constant explicit.

Thanks.

I have another question. I have a class with a timer than I want to turn on and off. So I put a dispatch_source_t timer in the @interface definition. But can I set this to nil in the init method of that class? Or is dispatch_source_t a primitive like float? If that is the case, how can I set it to a nil value so that I don't get memory leaks or undefined behaviour?

@interface aClass : NSObject {
	NSInteger *timeInterval;
	
	@private
		NSManagedObjectContext *moc;
		dispatch_source_t timer;
}

@implementation aClass
- (id) init
{
	self = [super init];
	if (self != nil) {
		timer = nil;
	}
	return self;
}

-(void) start
{
	if (!timer) {
                //run event handler on the default global queue
		timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)); 		
		
		//	dispatch_time_t now = dispatch_walltime(DISPATCH_TIME_NOW, 0);
		dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 3ull*NSEC_PER_SEC, 500ull);
		
		dispatch_source_set_event_handler(timer, ^{
			NSLog(@"asdf");
		});
		dispatch_resume(timer);
	} else {
		dispatch_resume(timer);
	}

}

 

[chown33]

I have another question. I have a class with a timer than I want to turn on and off. So I put a dispatch_source_t timer in the @interface definition. But can I set this to nil in the init method of that class? Or is dispatch_source_t a primitive like float? If that is the case, how can I set it to a nil value so that I don't get memory leaks or undefined behaviour?

You never have to set any instance-variable to nil, or 0, or 0.0, or { 0, 0 }, etc. When any object is alloc'ed, all its ivar memory is zeroed. This behavior is guaranteed. So by the time init sees a 'self', the ivars are already zeroed.

You'd only get a memory leak at dealloc, not init. Unless you over-assign and neglect to release or free something.

In general, there is no way to tell whether a given typedef is a pointer type or a non-pointer type. You have to look at the typedef itself. You can't tell if it's a scalar (like int, float, long long) or a composite (like struct or union), either, except by looking at the typedef.

 

[Detrius]

In general, there is no way to tell whether a given typedef is a pointer type or a non-pointer type. You have to look at the typedef itself. You can't tell if it's a scalar (like int, float, long long) or a composite (like struct or union), either, except by looking at the typedef.

It doesn't help much if you're sticking strictly to Objective-C, but if you're using C++, Boost has a library called Type Traits that will tell you this stuff about arbitrary types:

http://www.boost.org/doc/libs/1_43_...ml/boost_typetraits/reference/is_pointer.html

I have absolutely no idea how well this mixes with Objective-C objects, if at all, and I only bring it up because of the possibility of Objective-C++.