Open Radar

 
Summary:
The behavior of -[AVAssetWriter finishWritingWithCompletionHandler:] is different between iOS 6 and iOS 7 with regards to whether the calling object needs to retain a reference to the AVAssetWriter.

In iOS 6, if you retain a reference, the completion handler is never called; if you do not retain the reference, the completion handler gets called.

In iOS 7, the situation is the exact opposite. Retaining the AVAssetWriter results in the completion handler getting called.

Steps to Reproduce:
Build and run the attached project. There is a single view controller; the switch controls whether the AVAssetWriter is retained or not. The "Go!" button kicks off the build of the movie. On success, the movie is shown; on failure, the spinner just spins.


Expected Results:
I expect the behavior to be consistent between versions of iOS.

Actual Results:
I see different behavior between ios6 and 7 builds.

Version:
See above

Notes:
Workaround is to add a check based on the iOS version

Configuration:
Versions I have tested where retaining the AVAssetWriter is required:

Simulator running iOS7 32-bit
Simulator running iOS 7 64-bit
iPod Touch (ME643LL/A) running iOS 7.0 (11A465)
iPhone 4S (MD278LL/A) running iOS 7.0.2 (11A501)

Versions where the AVAssetWriter must not be retained:

Simulator running iOS 6.0
Simulator running iOS 6.1
iPod Touch (MC540LL/A) running iOS 6.1.3 (10B329)

(When submitting to Apple, I included repro source; cannot include here for NDA reasons.)