How do I use a TypeConverter in Gorp?

I would like to use Gorp to load and save structs from the DB that contain specialised types. Amongst other things, this is useful for enumerated strings such as roles:

type Role string

type Account struct {
    User string
    Role Role
}

This doesn't work "out of the box". An error message is raised such as

panic: sql: converting Exec argument #0's type: unsupported type user.Role, a string

I suspect I need to use a gorp.TypeConverter to solve this, but there is no documentation on how to do this.

Can you help?

Valuer and Scanner interfaces will do what you want. Here is a working example :

package roleGorp
import (
"gopkg.in/gorp.v1"
"github.com/DATA-DOG/go-sqlmock"
"fmt"
"testing"
"database/sql/driver"
)
type Role string
func (r *Role) Scan(value interface{}) error { *r = Role(value.(string)); return nil }
func (r Role) Value() (driver.Value, error)  { return string(r), nil }
type Account struct {
User string `db:"user"`
Role Role `db:"role"`
}
func TestRoleGorp(t *testing.T) {
db, err := sqlmock.New()
if err != nil {
panic(err)
}
dbMap := gorp.DbMap{
Db: db,
Dialect: gorp.MySQLDialect{
Engine: "InnoDB",
},
}
rows := sqlmock.NewRows([]string{"user", "role"}).AddRow("user1", "admin")
sqlmock.ExpectQuery(`SELECT \* FROM account LIMIT 1`).WillReturnRows(rows)
dbMap.AddTableWithName(Account{}, "account")
result := &Account{}
err = dbMap.SelectOne(result, "SELECT * FROM account LIMIT 1")
if err != nil {
panic(err)
}
fmt.Printf("%+v\n", *result)
result2 := &Account{
User: "user2",
Role: Role("moderator"),
}
sqlmock.ExpectExec("insert into `account` \\(`user`,`role`\\) values \\(\\?,\\?\\);").WithArgs("user2", "moderator").WillReturnResult(sqlmock.NewResult(1, 1))
err = dbMap.Insert(result2)
if err != nil {
panic(err)
}
}