I wrote a post a few months ago about sharing data between iOS apps and app extensions in which I recommended using NSFileCoordinator and NSFilePresenter. But I had to update the post to remove that portion when some helpful people pointed me to Apple Tech Note 2408, which read in part:

When you create a shared container for use by an app extension and its containing app in iOS 8, you are obliged to write to that container in a coordinated manner to avoid data corruption. However, you must not use file coordination APIs directly for this.

That basically meant that it was specifically unsafe to use these classes for what would seem to be one of their primary use cases. That sucked.

However last week the tech note was updated, and the above section now reads:

When you create a shared container for use by an app extension and its containing app in iOS 8.0 or later, you are obliged to write to that container in a coordinated manner to avoid data corruption. However, you must not use file coordination APIs directly for this in iOS 8.1.x and earlier. [emphasis mine]

That's great! In iOS 8.2 or higher, the obvious approach should now be safe. I've updated the original post to restore (and somewhat expand) the original discussion of file coordination.

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A large part of the Swift Standard Library is concerned with Generators, Sequences and Collections and functions that operate on them, so it’s pretty important to have a good understanding of them.

I was going to write a blog post about how to create and use Swift generators and sequences. But while I was trying to understand them myself, I found this post over at iOSDeveloperZone.

Go read that, and pretend that I wrote something as helpful.

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Over the past month or so I've been diving into Swift, after many years of working with Objective-C on Macs and iOS. It's been a change but, gradually, I'm learning the Swift way of doing things. On the way I've run into a few bumps in the road when dealing with Core Data, and I thought would be useful to share how I got past them. Xcode Generated Subclasses Considered Harmful This is the main impetus for this post. Most other stuff I would expect people to work around eventually, but this one is kind of big. Xcode's generated NSManagedObject subclasses are limited but useful in their own way. If you don't need much, they'll do. Everyone else would use mogenerator. That's if you're using Objective-C, though. With Swift there's a decent…

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Since iOS app extensions run as part of a host application rather than as part of their containing app (i.e. your app's extensions run in somebody else's app), data sharing isn't automatic. Finding standard locations like the documents directory doesn't work for shared data. In this post I'll go through the details of how to make it all work. Along the way I'll get into how to set up real-time messaging between apps and their extensions. Not Cocoa notifications, but a variation of file-based IPC that includes a notification system. Most of this is not actually specific to iOS extensions, though it's probably more useful with extensions than in other situations. Code snippets are included, and see GitHub for the full project. Sharing…

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iOSDevCamp Colorado was a couple of weeks ago and I did a presentation/demo on iOS app extensions. I wanted to focus on how to actually do things, so mostly I worked in Xcode rather than present from slides. But rather than paste code in as I went or (gasp!) try to do it live, I worked from a git repository I had built while developing the demo app. Every time I made a significant change, I'd commit it. During the presentation I would show some of what I was doing at each step and then jump ahead to the next commit to show the completed version. I like the idea but I need to work on doing it smoothly. One nice thing about it is that I can share the project and have it provide more information on the development process. Rather than just…

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