Rename the folder of document directory - iphone

Question

This could be easy, but I am not getting the problem.
I am using below code to rename the folders of document directory and is working fine except one case.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:#"Photos"];
NSArray * arrAllItems = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:dataPath error:NULL]; // List of all items
NSString *filePath = [dataPath stringByAppendingPathComponent:[NSString stringWithFormat:#"%#", [arrAllItems objectAtIndex:tagSelected]]];
NSString *newDirectoryName = txtAlbumName.text; // Name entered by user
NSString *oldPath = filePath;
NSString *newPath = [[oldPath stringByDeletingLastPathComponent] stringByAppendingPathComponent:newDirectoryName];
NSError *error = nil;
[[NSFileManager defaultManager] moveItemAtPath:oldPath toPath:newPath error:&error];
if (error) {
NSLog(#"%#",error.localizedDescription);
// handle error
}
Now, my problem is if there is a folder named "A"(capital letter A) and I am renaming it to "a" (small letter a), then it is not working and giving an error. I am not getting where the problem is.

Answer 1

The HFS+ file system (on OS X) is case insensitive, but case preserving.
That means if you create a folder "A" and then check if there is a folder "a", you will get
"yes" as an answer.
The file manager moveItemAtPath:toPath:... checks first if the destination path already
exists and therefore fails with
NSUnderlyingError=0x7126dc0 "The operation couldn’t be completed. File exists"
One workaround would be to rename the directory to some completely different name first:
A --> temporary name --> a
But a much easier solution is to use the BSD rename() system call, because that
can rename "A" to "a" without problem:
if (rename([oldPath fileSystemRepresentation], [newPath fileSystemRepresentation]) == -1) {
NSLog(#"%s",strerror(errno));
}
Note that the problem occurs only on the iOS Simulator, not on the device, because
the device file system is case sensitive.
Swift:
let result = oldURL.withUnsafeFileSystemRepresentation { oldPath in
newURL.withUnsafeFileSystemRepresentation { newPath in
rename(oldPath, newPath)
}
}
if result != 0 {
NSLog("%s", strerror(errno))
}