How to update progress bar while large math function executed (objective-c)?

Question

I have math function (about O^(10^7)) and while it searching result I have to display progress. So I have progress bar. The question is, how to update progress bar? I have tried to do it so:

self.progressBar.progress = 0.0;
self->progress = 0.0;
for (1..10^7) {
    ...
    if (self.progressBar.progress < self.progress + 0.01) {
        [self updateProgress];
    }
}
[self updateProgress];

looks like it's unreal to write code on stackoverflow via iphone :( — Timur Bernikovich, Mar 29 '13 at 21:59
- (void)updateProgress { [self.progressBar setProgress:self->progress animated:YES];} — Timur Bernikovich, Mar 29 '13 at 22:00
i have tried to use performSelectorOnMainStream too.. and dispatch_async — Timur Bernikovich, Mar 29 '13 at 22:05
Do calculation in background thread. After each unit of your calculation, send a notification using nsnotificationcenter. Some object can then observe the notification and update the progress. — Jeremy, Mar 29 '13 at 22:09
in my country it's mean 10 000 000 operations or O^(10^7) time, where O - time for 1 operation — Timur Bernikovich, Mar 29 '13 at 22:22
I use this technique when download large files and I use indicator to show % complete. — Jeremy, Mar 29 '13 at 22:27
@timurka13let I don't know what kind of notation is that, but it's confusing because it looks like [Big O notation](http://en.wikipedia.org/wiki/Big_O_notation). Please don't use it. — Sulthan, Mar 29 '13 at 22:51

score 2 · Accepted Answer · answered Mar 29 '13 at 22:12

Run the operation in a separate thread. That's a must.

Can you divide the operation into steps? Do you know the number of steps? Then update progress bar after every step to stepIndex/numSteps percents.

If you can't divide the operation into steps but you know how long the operation will take, you can update the bar to timeSinceStart/expectedTime percents. Use a NSTimer for the periodic updates.

If you can't do that, use only a UIActivityIndicator, that is, a component that shows the application is doing something but showing no indication how long the operation can take.

I did it with performSelectorOnBackground (for calc.) and in background performSelectorInMainThread (for UI)! — Timur Bernikovich, Mar 29 '13 at 22:52

score 1 · Answer 2 · answered Mar 29 '13 at 22:06

Sometimes you have to do:

CFRunLoopRunInMode (CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent()), 0, FALSE);

To get the UI to update the progress bar.

Also.. you have animated:YES and that's not available in all versions of iOS.

You might want to consider instead in your updateProgress method:

if ([activityProgressView respondsToSelector:@selector(setProgress:animated:)]) {
    [activityProgressView setProgress:0.5 animated:YES];
}
else {
    [activityProgressView setProgress:0.5];
}
CFRunLoopRunInMode (CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent()), 0, FALSE);

How to update progress bar while large math function executed (objective-c)?

2 Answers2