Question

Hey there, I am fresh to iPhone development and Objective C. Sorry if this question is too stupid….

Here is my problem, I want to calculate the time taken by one of my function. like UIGetScreenImage. Here is the code:

-(void)screenCapture{
   CGImageRef screen = UIGetScreenImage();
   UIImage* image = [UIImage imageWithCGImage:screen];
   CGImageRelease(screen);
   UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
}

what should I do to calculate the time taken by this process? Sample code would be appreciated.

Thanks for your kind assistance. Look forward to your replies and ideas. 😀

Answer 1

You can get current date on method start and finish and check time passed between those 2 moments:

-(void)screenCapture{
NSDate* startDate = [NSDate date];
…
NSDate* finishDate = [NSDate date];
NSLog(@”%f”, [finishDate timeIntervalSinceDate: startDate]);
}

Edit: I believe my approach described above is (to put it mildly) not the best solution to measure process time. Now I use approach described in “Big Nerd Ranch” blog here that uses mach_absolute_time function. I copied the code from the post to illustrate that method – with this code snippet you can measure rub time of arbitrary block:

#import <mach/mach_time.h>  // for mach_absolute_time() and friends

CGFloat BNRTimeBlock (void (^block)(void)) {
    mach_timebase_info_data_t info;
    if (mach_timebase_info(&info) != KERN_SUCCESS) return -1.0;

    uint64_t start = mach_absolute_time ();
    block ();
    uint64_t end = mach_absolute_time ();
    uint64_t elapsed = end - start;

    uint64_t nanos = elapsed * info.numer / info.denom;
    return (CGFloat)nanos / NSEC_PER_SEC;

} // BNRTimeBlock