NSFileCoordinator Improvement in iOS 8.2
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.
NSDictionaryhas awriteToURL: 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
FolderWatcherclass 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.
