Rich value types in Golang

main.go

package main

import (
	"database/sql"
	"database/sql/driver"
	"errors"
	"fmt"
	"log"
	"strconv"
	"strings"

	_ "github.com/mattn/go-sqlite3"
)

// Point our point type.
type Point struct {
	X int
	Y int
	Z int
}

// String converts the Point to a string.
func (e Point) String() string {
	return fmt.Sprintf("%d:%d:%d", e.X, e.Y, e.Z)
}

// Value function is called when the data is inserted on the database.
func (e Point) Value() (driver.Value, error) {
	return driver.Value(e.String()), nil
}

// Scan function will be called when the db.Scan function is called.
func (e *Point) Scan(src interface{}) error {
	var (
		source string
		ok     bool
		err    error
	)

	if source, ok = src.(string); !ok {
		return errors.New("incompatible type for Point, it must be a string")
	}

	parts := strings.Split(source, ":")
	if len(parts) != 3 {
		return errors.New("incompatible type for Point, it must be formatted as x:y:z")
	}

	point := Point{}

	point.X, err = strconv.Atoi(parts[0])
	if err != nil {
		return errors.New("incompatible type for Point, x must be a number")
	}

	point.Y, err = strconv.Atoi(parts[1])
	if err != nil {
		return errors.New("incompatible type for Point, y must be a number")
	}

	point.Z, err = strconv.Atoi(parts[2])
	if err != nil {
		return errors.New("incompatible type for Point, z must be a number")
	}

	*e = point
	return nil
}

func main() {
	// Getting the sqlite database
	db, err := sql.Open("sqlite3", "file:foo.db")

	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Creating the points table
	_, err = db.Exec(`CREATE TABLE IF NOT EXISTS points (
						id INTEGER PRIMARY KEY AUTOINCREMENT,
						point TEXT
					  )`)

	if err != nil {
		log.Fatal(err)
	}

	_, err = db.Exec("DELETE FROM points")

	if err != nil {
		log.Fatal(err)
	}

	// Inserting two users on the database
	_, err = db.Exec("INSERT INTO points (point) VALUES (?), (?)",
		Point{X: 1, Y: 2, Z: 3}, Point{X: 4, Y: 5, Z: 6})

	if err != nil {
		log.Fatal(err)
	}

	// Querying points table
	rows, err := db.Query("SELECT * FROM points")

	if err != nil {
		log.Fatal(err)
	}

	defer rows.Close()

	for rows.Next() {
		var id int64

		// Using Point the conversion will be transparent
		var point Point

		err = rows.Scan(&id, &point)

		if err != nil {
			log.Println(err)
		}

		log.Println(point)
	}
}