get all / list all folders in directory

+(NSArray*)arrayOfFoldersInFolder:(NSString*) folder {
	NSFileManager *fm = [NSFileManager defaultManager];
	NSArray* files = [fm directoryContentsAtPath:folder];
	NSMutableArray *directoryList = [NSMutableArray arrayWithCapacity:10];
 
	for(NSString *file in files) {
		NSString *path = [folder stringByAppendingPathComponent:file];
		BOOL isDir = NO;
		[fm fileExistsAtPath:path isDirectory:(&isDir)];
		if(isDir) {
			[directoryList addObject:file];
		}
	}
 
	return directoryList;
}