NSFileManager

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [paths objectAtIndex:0];
NSString *secondaryDirectoryPath = [documentsDirectoryPath stringByAppendingPathComponent:@"secondary"];
NSString *databaseFile = [secondaryDirectoryPath stringByAppendingPathComponent:@"database.db"];

NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager removeItemAtPath:databaseFile error:NULL];