func searchContactByID(_ id: Int) -> Contact? {
  let queryString = "SELECT * FROM Contact WHERE ID = \(id)"

  // Execute query and save the results.
  let queryResults: FMResultSet? = mainDB?.executeQuery(queryString, withArgumentsIn: nil)

  // Check if there are results.
  if queryResults?.next() == true {
    let contactName = queryResults!.string(forColumn: "Name")
    let contactPhone = Int(queryResults!.int(forColumn: "Phone"))
    let contactCity = queryResults!.string(forColumn: "City")

    return Contact(id: id, name: contactName, phoneNumber: contactPhone, city: contactCity)
  }

  // No matching results.
  return nil
}

func searchContactByName(_ name: String) -> [Contact] {
  let queryString = "SELECT * FROM Contact WHERE Name = \(name)"
  let queryResults: FMResultSet? = mainDB?.executeQuery(queryString, withArgumentsIn: nil)

  // Save the results into an array.
  var results = [Contact]()

  while queryResults?.next() == true {
    let contactID = Int(queryResults!.int(forColumn: "ID"))
    let contactPhone = Int(queryResults!.int(forColumn: "Phone"))
    let contactCity = queryResults!.string(forColumn: "City")

    // Append the result to the results array.
    results.append(Contact(id: contactID, name: name, phoneNumber: contactPhone, city: contactCity))
  }

  return results
}