Direct assignment:
NSTimeInterval interval = 1002343.5432542;
NSInteger time = interval;
//time is now equal to 1002343
NSTimeInterval is a double, so if you assign it directly to a NSInteger (or int, if you wish) it’ll work. This will cut off the time to the nearest second.
If you wish to round to the nearest second (rather than have it cut off) you can use round before you make the assignment:
NSTimeInterval interval = 1002343.5432542;
NSInteger time = round(interval);
//time is now equal to 1002344