I have no idea how many weeks I have wasted debugging issues that come down to this problem. I am pretty mad at myself for forgetting this, but oh boy, it’s not gonna happen anymore. Oh no.

Ok, so you have NSFetchedResultsController driving either a collection view or table view. And when customer is looking at those views, you want the changes to animate in/out, as Apple has ask us to do since the days when iOS was called iPhone OS. To do that, you need to implement the four horsemen of NSFetchedResultsControllerDelegate methods.

However - and this is the trick - you don’t need to do that when those views are not visible. You only need to call reloadData on end of changes. However, I guarantee you that 95% of iOS devs leave those four methods as they are. And experience hair-pulling mind-cracking EXC_BAD_ACCESS crashes all over the place, in darn background threads that cause postNotification:..:... and what not. And you have questions about this on StackOverflow being answered with

oh, just set self.fetchedResultsController.delegate to nil in viewWillDisappear and problem goes away. Re-set it on viewWillAppear

You don’t say! Well, it sure goes away, but you also lose all the changes and your views do not reflect the current state of data source. And then when you try to animate, more crashes ensue…

oh, that’s easy to fix. Just add [self.collectionView reloadData] in viewWillAppear…

AAARRGGHHH!

No. Do not do any of that crap.

My little experiment measuring the influence of downloads to the search ranking gave me an interesting look at current state of iPhone devices in the wild. While 60k is far cry from hundreds of millions of estimated target base, it offers good glimpse into what people that actively look for apps are using as devices.

It also exemplifies how important localization is, which I’ll address first.

Currency converter niche on the App Store is terribly crowded space. When you search for currency on the App Store, you get 2200+ results. Searching for currency converter gives you 840 results. My currency converter app - Banca - was ranked around 35-40th position when using these keywords, which is next to infinity in current cards-layout of the search results in the App Store app. Up to this point, Banca had 140k downloads (it’s on the store for two years).

Thus on January 17th, I organized a promotion where Banca would be free and I aimed to get as high number of downloads as I can in a short space of time. I wanted to see how much I can move that needle.

Results are not spectacular, but are still significant enough.

Custom view controller transitions are fast becoming my favourite iOS 7 API addition. As with all new things, there are surprises and side effects to learn about. This post is about one such issue, in this triangle: