From 8a6acecfab2879ba4e26487c99f204ede8b3d935 Mon Sep 17 00:00:00 2001 From: Inada Naoki Date: Sat, 5 Aug 2023 16:22:48 +0000 Subject: database/sql: add Null[T] Generic version of NullString, NullInt64, etc. Fixes #60370 Change-Id: I166a05a6126e8b8571db5cbb026303bb6551d56b GitHub-Last-Rev: 3c8d2d5141c36f034d2124e19ee090620363ba24 GitHub-Pull-Request: golang/go#60677 Reviewed-on: https://go-review.googlesource.com/c/go/+/501700 Reviewed-by: Jonathan Amsterdam TryBot-Result: Gopher Robot Run-TryBot: Ian Lance Taylor Reviewed-by: Russ Cox --- src/database/sql/sql.go | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'src/database/sql/sql.go') diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go index 836fe83e2e..7a57c7de36 100644 --- a/src/database/sql/sql.go +++ b/src/database/sql/sql.go @@ -391,6 +391,39 @@ func (n NullTime) Value() (driver.Value, error) { return n.Time, nil } +// Null represents a value that may be null. +// Null implements the Scanner interface so +// it can be used as a scan destination: +// +// var s Null[string] +// err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&s) +// ... +// if s.Valid { +// // use s.V +// } else { +// // NULL value +// } +type Null[T any] struct { + V T + Valid bool +} + +func (n *Null[T]) Scan(value any) error { + if value == nil { + n.V, n.Valid = *new(T), false + return nil + } + n.Valid = true + return convertAssign(&n.V, value) +} + +func (n Null[T]) Value() (driver.Value, error) { + if !n.Valid { + return nil, nil + } + return n.V, nil +} + // Scanner is an interface used by Scan. type Scanner interface { // Scan assigns a value from a database driver. -- cgit v1.3