On a complete tangent, are you calling a stored procedure there? I thought
the database/sql package didn't support MySQL stored procedures yet?
On Monday, June 5, 2017 at 5:43:33 PM UTC+1, Ren Thraysk wrote:
>
>
> Wrote something similar recently.
>
> One difference is that I moved the rows.Scan call into the passed in
> function.
>
>
> type Scannable interface {
> Scan(...interface{}) error
> }
>
> func scanIntoUser(u *store.User) func(s Scannable) error {
> return func(s Scannable) error {
> return s.Scan(&u.Id, &u.Name, &u.PasswordHash, &u.Email)
> }
> }
>
> func (s *userStore) UserByName(name string) (*store.User, error) {
> u := &store.User{}
> err := ExpectOneRow(s.db, scanIntoUser(u), "CALL spUserByName(?)", name)
> if err != nil {
> return nil, err
> }
> return u, nil
> }
>
>
> Idea being gives an opportunity to do some mapping by scanning into local
> variables and then assign them into the object, for instance dealing with
> NULLs. Scan into a sql.Null* variable, and modify whatever struct as see
> appropriate.
>
> Ren
>
>
>
>
> On Friday, 2 June 2017 13:55:12 UTC+1, brylant wrote:
>>
>>
>> I've been trying hard (well.. as much as I can considering my lack of
>> in-depth go knowledge or - to be perfectly honest - lack of in-depth
>> knowledge of anything) to find suitable go+sql technique that would not
>> require a lot of code repetition, not use reflection and not use ORMs of
>> any sort... Could somebody please tell me if there's anything particularly
>> wrong with the following:
>>
>>
>> type ScannerFunc func() []interface{}
>>
>> func (db *DB) ScanSome(stmt string, sf ScannerFunc, params ...interface{})
>> error {
>> rows, err := db.Query(stmt, params...)
>> if err != nil {
>> return err
>> }
>> defer rows.Close()
>> for rows.Next() {
>> err = rows.Scan(sf()...)
>> if err != nil {
>> return err
>> }
>> }
>> if err = rows.Err(); err != nil {
>> return err
>> }
>> return nil
>> }
>>
>> Having the above I could then implement the following for each of my
>> 'models' (User being an example below). This could easily be 'go
>> generate'-d for each model
>>
>>
>> type User struct {
>> UserID int64
>> Name string
>> Role int
>> // (...)
>> }
>>
>> func ScanUsersFunc(users *[]*User) ScannerFunc {
>> return ScannerFunc(func() []interface{}) {
>> u := User{}
>> *users = append(*users, &u)
>> var r []interface{} = []interface{}{&u.UserID, &u.Name, &u.Role,
>> (more properties)}
>> return r
>> }
>> }
>>
>>
>> and finally use it like this:
>>
>>
>> const (
>> sqlUsersByRole = "SELECT user_id,name,role, (more if needed) FROM
>> user WHERE role=?"
>> sqlAllUsers = "SELECT user_id,name,role FROM user"
>> )
>>
>> func (db *DB) UsersByRole(role int) ([]*User, error) {
>> users := make([]*User, 0)
>> err := db.ScanSome(sqlUsersByRole, ScanUsersFunc(&users), role)
>> if err != nil {
>> return nil, err
>> }
>> return users, nil
>> }
>>
>> func (db *DB) AllUsers() ([]*User, error) {
>> users := make([]*User, 0)
>> err := db.ScanSome(sqlAllUsers, ScanUsersFunc(&users))
>> if err != nil {
>> return nil, err
>> }
>> return users, nil
>> }
>>
>>
>> Alternatively (to avoid scanning/returning all results) a callback could
>> be provided to ScanSome and called after each scan.
>>
>> Obviously I could also implement ScanOne for situations where I only
>> expect one row of results...
>>
>>
>> So - any obvious issues with the above 'technique'...?
>>
>>
>> Thanks,
>>
>> adam
>>
>>
>>
>>
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