On Mar 10, 2011, at 1:33 AM, Jeffrey Walton wrote:
> Hi All,
>
> I've got a method that refreshes a list of files in a directory. The
> code executes properly on the first invocation, but crashes on the
> second invocation. The cause of the crash is walker = [fileManager
> enumeratorAtPath:directory].
>
> Any ideas on the cause? I experience the crash with both methods of
> retrieving the file manager. Are there known issues with
> enumeratorAtPath?
Form the snipped below, I cannot see a memory management error. It doesn't
mean, there is none, though. The object 'walker' *should* be valid unless you
access it *after* you released 'fileManager'.
It not at all looks like a concurrency issue or race condition related problem
stemming from the framework. If there is an issue in the framework, it may only
happen when you simultaneously alter the contents of the directory in a
different thread while you iterating through it in your code.
So, I suspect the error is elsewhere, it may be "thread-related" if you do such
things - but it's most likely still in your code ;)
Nonetheless, after you carefully reviewed your code, and couldn't find the
error I would resort to check a thread-safety related issue within Cocoa as
well.
Andreas
>
> Jeff
>
> NSString* directory = nil;
> NSFileManager* fileManager = nil;
> NSDirectoryEnumerator* walker = nil
>
> directory = [NSHomeDirectory()
> stringByAppendingPathComponent:@"Documents"];
> if(directory == nil)
> /* handle error and exit */
>
> // fileManager = [NSFileManager defaultManager];
> fileManager = [[NSFileManager alloc] init];
> if(fileManager == nil)
> /* handle error and exit */
>
> walker = [fileManager enumeratorAtPath:directory];
> if(walker == nil)
> /* handle error and exit */
>
> NSString* file = nil;
> while((file = [walker nextObject]) != nil)
> {
> BOOL isDirectory = YES;
> if([fileManager fileExistsAtPath:file
> isDirectory:&isDirectory] && !isDirectory)
> [files addObject:file];
> }
>
> ...
>
> [fileManager release];
>
> *****
>
> According to 'NSFileManager Class Reference'
> (http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSFileManager_Class/Reference/Reference.html):
>
> In iOS and Mac OS X v 10.5 and later you should consider
> using [[NSFileManager alloc] init] rather than the singleton
> method defaultManager. Instances of NSFileManager are
> considered thread-safe when created using
> [[NSFileManager alloc] init].
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