+(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;
}

- (ViewController *) init {
    if (self = [super init]) self.title = @"Text Files";

    // get the list of all files and directories
    NSFileManager *fM = [NSFileManager defaultManager];
    fileList = [[fM directoryContentsAtPath:DOCUMENTS_FOLDER] retain];
    NSMutableArray *directoryList = [[NSMutableArray alloc] init];
    for(NSString *file in fileList) {
        NSString *path = [DOCUMENTS_FOLDER stringByAppendingPathComponent:file];
        BOOL isDir = NO;
        [fM fileExistsAtPath:path isDirectory:(&isDir)];
        if(isDir) {
            [directoryList addObject:file];
        }
    }

    NSLog(@"%@", directoryList);

    return self;
}

get all / list all folders in directory

Objective C