Apple suggests using an instance of NSFileManager class and avoid the static class method defaultManagerbecause it will return a singleton instance: no thread-safe:

In Mac OS X v.10.5 and later you should consider using [[NSFileManager alloc] init] rather than the singleton method defaultManager. Using [[NSFileManager alloc] init] instead, the resulting NSFileManager instance is thread safe.

For example:

// bad
BOOL result = [[NSFileManager defaultManager] fileExistsAtPath:pathLocalRepository isDirectory:nil];

// good
NSFileManager *fm = [[NSFileManager alloc] init];
BOOL result = [fm fileExistsAtPath:pathLocalRepository isDirectory:nil];
[fm release];
fm = nil;