NSFileManager -replaceItemAtURL:... fails with no explanation

Originator:google
Number:rdar://9993350 Date Originated:8/21/2011
Status: Resolved:
Product:iPad SDK Product Version:4.3
Classification:Other Bug Reproducible:Always
 
Summary:
When attempting to replace a file in an iPad app's Documents directory with another file using -[NSFileManager replaceItemAtURL:withItemAtURL:backupItemName:options:resultingItemURL:error:], the operation fails (returns NO), but does not set the error parameter to explain why.

Steps to Reproduce:
- Create a file in a subdirectory of Documents (e.g. Documents/Subdir/foo.txt)
- Create a file elsewhere (e.g. in the app's Caches directory, or NSTemporaryDirectory())
- Construct NSURL instances pointing to those files
- Call -[NSFileManager replaceItemAtURL:withItemAtURL:backupItemName:options:resultingItemURL:error:] to replace one file with the other

Expected Results:
The method either returns YES to indicate success, or sets the error parameter to an NSError instance that explains the cause of the failure.

Actual Results:
The method returns NO, and does not set the error parameter. (And if the pointer passed in is not initialized, it will still contain garbage upon return.)

Regression:

Notes:
Sample code attached. Results observed in 4.3 simulator both in Xcode 4.0.2 on Snow Leopard and 4.1 on Lion.

Comments


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