Tuesday, May 19, 2015 [Tweets] [Favorites]

NSFileCoordinator Improvement in iOS 8.2

Tom Harrington (tweet):

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.

Previously: iOS IPC via NSFileCoordinator and NSFilePresenter.

Update (2015-07-28): Richard Turton:

This dictionary can then be written to a specified location in the shared folder. The write has to be atomic, to ensure that the other processes don’t start reading the file before it is written. NSDictionary has a writeToURL: atomically: method that can be used for this.

Interested members of the app group can then detect the writing of this file by monitoring a folder using GCD. The details of this can be seen in the FolderWatcher class in the linked project.

[…]

The limitations of the Darwin Notification Centre and the complexities of writing to and reading from a file make the above solution suitable for only a small number of cases.

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