new QueryData using generic Scanner interface (for assigning struct items)

storage/sql/sql.go

@@ -10,7 +10,10 @@ type Cfg struct {
 	Driver, Connstr string
 }
 
+type Rows = sql.Rows
+
 type rowsProc = func(*sql.Rows) error
+type Scanner interface{ Scan(*Rows) (Scanner, error) }
 
 type Storage struct {
 	*sql.DB
@@ -25,7 +28,20 @@ func Open(cfg *Cfg) *Storage {
 	return &Storage{db}
 }
 
-func QueryData[T any](db *Storage, q string, args ...interface{}) []T {
+func QueryData[T Scanner](db *Storage, q string, args ...interface{}) []T {
+	var data []T
+	proc := func(r *sql.Rows) error {
+		var rec T
+		r1, err := rec.Scan(r)
+		rec = r1.(T)
+		data = append(data, rec)
+		return err
+	}
+	db.Query(proc, q, args...) // ?? check error
+	return data
+}
+
+func QueryCol[T any](db *Storage, q string, args ...interface{}) []T {
 	var data []T
 	proc := func(r *sql.Rows) error {
 		var rec T
@@ -33,7 +49,7 @@ func QueryData[T any](db *Storage, q string, args ...interface{}) []T {
 		data = append(data, rec)
 		return err
 	}
-	db.Query(proc, q, args...)
+	db.Query(proc, q, args...) // ?? check error
 	return data
 }
 

tests/storage_test.go

@@ -30,12 +30,23 @@ func DoTests(t *testing.T, cfg *sql.Cfg, db *sql.Storage) {
 	t.Run("base", func(t *testing.T) { BaseTest(t, cfg, db) })
 }
 
+type greet struct {
+	id    int64
+	label string
+}
+
+func (g greet) Scan(rows *sql.Rows) (sql.Scanner, error) {
+	err := rows.Scan(&g.id, &g.label)
+	return g, err
+}
+
 func BaseTest(t *testing.T, cfg *sql.Cfg, db *sql.Storage) {
 	//fmt.Println(cfg.Connstr)
 	db.Exec(insert)
-	data := sql.QueryData[string](db, query, 2)
+	//data := sql.QueryCol[string](db, query, 2)
+	data := sql.QueryData[greet](db, query, 2)
 	t.AssertEqual(len(data), 1)
-	t.AssertEqual(data[0], "Good Afternoon")
+	t.AssertEqual(data[0].label, "Good Afternoon")
 }
 
 func resetSqlite(db *sql.Storage) {
@@ -56,7 +67,7 @@ var insert = `insert into test (label) values
 	('Hello World'),
 	('Good Afternoon')`
 
-var query = `select label from test 
+var query = `select id, label from test 
 	where id = $1`
 
 // database-specific SQL statements