英文:
How do I use a TypeConverter in Gorp?
问题
我想使用Gorp从数据库中加载和保存包含特殊类型的结构体。其中之一是用于枚举字符串（如角色）：
type Role stringtype Account struct {User stringRole Role}
这在“开箱即用”情况下无法正常工作。会引发错误消息，例如：
panic: sql: converting Exec argument #0's type: unsupported type user.Role, a string
我怀疑我需要使用gorp.TypeConverter来解决这个问题，但是没有关于如何做到这一点的文档。
你能帮忙吗？
英文:
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 stringtype Account struct {User stringRole 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?
答案1
得分: 2
Valuer和Scanner接口可以实现你想要的功能。以下是一个可工作的示例：
package roleGorpimport ("gopkg.in/gorp.v1""github.com/DATA-DOG/go-sqlmock""fmt""testing""database/sql/driver")type Role stringfunc (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)}}
英文:
Valuer and Scanner interfaces will do what you want. Here is a working example :
package roleGorpimport ("gopkg.in/gorp.v1""github.com/DATA-DOG/go-sqlmock""fmt""testing""database/sql/driver")type Role stringfunc (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)}}
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