Added workaround for a bug in UIDatePicker in count down mode.

[tomaskraina]

A solution proposed by Positron on http://stackoverflow.com/a/20204317/1161723

This fixes #104

[skywinder]

Thanks for contribution.
Your commit broke a couple tests in the project https://travis-ci.org/skywinder/ActionSheetPicker-3.0/builds/42542107
I need to find out why the tests are failing now.

[tomaskraina]

Is there any way I could help with that?

[skywinder]

You can look at the failing tests inside the project:

-[ActionSheetDatePickerTestCase testPickerCountDownTimerModeValueWithBlock]
-[ActionSheetDatePickerTestCase testPickerCountDownTimerModeValueWithSelector]

If you have idea, why it fails now - please, let me know.

[skywinder]

It's really strange behaviour (so, we need do to async assignment in main thread from main thread).

So, nevertheless - my test start to failing after that fix.

It happens, because that tests execute pressDoneButton immediately from main thread - and when you wrap it to async the value doesn't change in that short period.
I suppose it's very rare case, because user can't press the button instantly, but it is a potential bug.

As workaround - It's possible to not replace my assignment with yours async, but add it after. i.e. do the same work twice. In that case tests work as expected.

I believe thinks there is should be a better solution.

[skywinder]

There is 2 solutions that I found:

1. add that code instead of yours replace:

 datePicker.countDownDuration = self.countDownDuration;
 dispatch_async(dispatch_get_main_queue(), ^{
 datePicker.countDownDuration = self.countDownDuration;
 });

1. Run test with fake delay:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [NSThread sleepForTimeInterval:0.5f];
        dispatch_async(dispatch_get_main_queue(), ^{
            [_actionSheetDatePicker pressDoneButton];
        });
    });

[skywinder]

Please add to that pull-request my fixes from tomaskraina-master branch and I will ready to merge it.

[tomaskraina]

Is it okay like this?

[skywinder]

Perfect! 👍