Hi,
this is answered (to a degree) in the FAQ:
https://golang.org/doc/faq#covariant_types
On Mon, Feb 1, 2021 at 2:51 PM Miha Vrhovnik <miha.vrhov...@gmail.com>
wrote:
>
> I'm trying to put external library under the interface but it seems that
> this is not possible the way I thought it would be...
>
> My interfaces are as following...
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> *type Beginner interface { Begin(ctx context.Context) (Tx, error)}type
> Querier interface { Exec(ctx context.Context, sql string, arguments
> ...interface{}) (commandTag pgconn.CommandTag, err error) Query(ctx
> context.Context, sql string, args ...interface{}) (pgx.Rows, error)
> QueryRow(ctx context.Context, sql string, args ...interface{})
> pgx.Row}type Tx interface { Commit(ctx context.Context) error
> Rollback(ctx context.Context) error Querier}*
>
> Now I have a function....
>
>
> *func NewFoo (b Beginer) {}*
>
> Into that function I want to pass a struct instance with the method that
> has a following signature. (This function is not under my control).
>
> *Begin(ctx context.Context) (pgx.Tx, error)*
>
> Now the* pgx.Tx* has a following signature
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> *type Tx interface { Begin(ctx context.Context) (Tx, error)
> Commit(ctx context.Context) error Rollback(ctx context.Context) error
> CopyFrom(ctx context.Context, tableName Identifier, columnNames []string,
> rowSrc CopyFromSource) (int64, error) SendBatch(ctx context.Context, b
> *Batch) BatchResults LargeObjects() LargeObjects Prepare(ctx
> context.Context, name, sql string) (*pgconn.StatementDescription, error)
> Exec(ctx context.Context, sql string, arguments ...interface{})
> (commandTag pgconn.CommandTag, err error) Query(ctx context.Context, sql
> string, args ...interface{}) (Rows, error) QueryRow(ctx context.Context,
> sql string, args ...interface{}) Row // Conn returns the underlying
> *Conn that on which this transaction is executing. Conn() *Conn}*
>
> The go is giving me the following error.
>
> cannot use me.DBpgx() (type *pgxpool.Pool) as type db.Beginner in argument
> to service.NewFoo:
> *pgxpool.Pool does not implement db.Beginner (wrong type for Begin
> method)
> have Begin(context.Context) (pgx.Tx, error)
> want Begin(context.Context) (db.Tx, error)
>
> how come that this is forbidden as my Tx interface is clearly a subset of
> pgx.Tx
>
> BR,
> Miha
>
> --
> You received this message because you are subscribed to the Google Groups
> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-nuts+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/golang-nuts/9fc0ff89-867a-464b-a955-07a63eec4296n%40googlegroups.com
> <https://groups.google.com/d/msgid/golang-nuts/9fc0ff89-867a-464b-a955-07a63eec4296n%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAEkBMfFDoJJ%2BNW5nsZqkJeScK%2BkirP99XPHnpS%2BoK4UPH2POAQ%40mail.gmail.com.
