QueryData: keep both variants of scan method: call by value, call by reference (pointer)

storage/sql/sql.go

@@ -10,17 +10,18 @@ type Cfg struct {
 	Driver, Connstr string
 }
 
+type Storage struct {
+	*sql.DB
+}
+
 type Rows = sql.Rows
 
 type rowsProc = func(*sql.Rows) error
-type scanner interface{ Scan(*Rows) error }
+type scn[T any] interface{ Scan(*Rows) (T, error) }
-type sccon[T any] interface {
+type scp interface{ ScanP(*Rows) error }
+type scpcon[T any] interface {
 	*T
-	scanner
+	scp
-}
-
-type Storage struct {
-	*sql.DB
 }
 
 func Open(cfg *Cfg) *Storage {
@@ -32,11 +33,23 @@ func Open(cfg *Cfg) *Storage {
 	return &Storage{db}
 }
 
-func QueryData[P sccon[T], T any](db *Storage, q string, args ...interface{}) []T {
+func QueryData[T scn[T]](db *Storage, q string, args ...interface{}) []T {
+	var data []T
+	var rec T
+	proc := func(r *sql.Rows) error {
+		rec, err := rec.Scan(r)
+		data = append(data, rec)
+		return err
+	}
+	db.Query(proc, q, args...) // ?? check error
+	return data
+}
+
+func QueryDataP[P scpcon[T], T any](db *Storage, q string, args ...interface{}) []T {
 	var data []T
 	rp := P(new(T))
 	proc := func(r *sql.Rows) error {
-		err := rp.Scan(r)
+		err := rp.ScanP(r)
 		data = append(data, *rp)
 		return err
 	}

tests/storage_test.go

@@ -35,14 +35,23 @@ type greet struct {
 	label string
 }
 
-func (g *greet) Scan(rows *sql.Rows) error {
+func (g greet) Scan(rows *sql.Rows) (greet, error) {
+	err := rows.Scan(&g.id, &g.label)
+	return g, err
+}
+
+func (g *greet) ScanP(rows *sql.Rows) error {
 	return rows.Scan(&g.id, &g.label)
 }
 
 func BaseTest(t *testing.T, cfg *sql.Cfg, db *sql.Storage) {
 	db.Exec(insert)
 	//data := sql.QueryCol[string](db, query, 2)
-	data := sql.QueryData[*greet](db, query)
+	data := sql.QueryData[greet](db, query)
+	t.AssertEqual(len(data), 2)
+	t.AssertEqual(data[0].label, "Hello World")
+	t.AssertEqual(data[1].label, "Good Afternoon")
+	data = sql.QueryDataP[*greet](db, query)
 	t.AssertEqual(len(data), 2)
 	t.AssertEqual(data[0].label, "Hello World")
 	t.AssertEqual(data[1].label, "Good Afternoon")