Update: I've found something similar in pkgsite
https://github.com/golang/pkgsite/blob/beceacdece62d95d6dc41a9b5f09da7b2a021020/internal/database/reflect.go
so I now assume it's not as far fetched as I thought until now.
Peter Müller schrieb am Freitag, 3. März 2023 um 16:53:07 UTC+1:
> Hello, would you assess the following usage of `Var[T any]`, `v =
> new(Var[T])` and `var person = rel.NewVar[Person]("person")` as valid
> pattern, that also enables it to be used in further generic methods, or
> would you rather prefer a codegen approach?
>
> ```go
> type Var[T any] struct {
> name string
> attributeNames []string
> typ reflect.Type
> }
>
> func NewVar[T any](name string) (v *Var[T]) {
> v = new(Var[T])
> v.name = name
>
> var typ *T
> v.typ = reflect.TypeOf(typ).Elem()
> v.attributeNames = make([]string, v.typ.NumField())
> for i := 0; i < v.typ.NumField(); i++ {
> v.attributeNames[i] = v.typ.Field(i).Tag.Get("db")
> }
>
> return v
> }
> ```
>
> Example:
>
>
> ```go
> import "github.com/peter-mueller/rel"
>
> type Person struct {
> Name string `db:"name"`
> Age int `db:"age"`
> }
>
> var personRel = rel.NewVar[Person]("person")
>
> func InsertGeneric[T any](v *rel.Var[T], value T) (stmt string, params
> []any) {
> stmt += fmt.Sprintf("INSERT INTO %s (%s)\n", v.Name(),
> strings.Join(v.AttributeRef(), ", "))
> stmt += fmt.Sprintf("VALUES (%s)\n", strings.Join(v.Params("?"), ","))
> params = v.Tuple(value)
> return stmt, params
> }
>
> // compiler checks if a Person struct is inserted into the relvar
> stmt, params := InsertGeneric(personRel, Person{"Ann", 21})
> res, err := db.ExecContext(ctx, stmt, params...)
> ```
>
> I think a non-generic alternative use would be to pass a empty struct
> value, but then the compiler can't check the types on inserts :
>
> ```go
> var personRel = rel.NewVar("person", Person{})
> Insert(personRel, Person{"Ann", 21})
> Insert(personRel, 12)
> ```
>
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