Extending Bun with custom types

Bun uses database/sql to work with different DBMS and so you can extend it with custom types using sql.Scanner and driver.Valuer interfaces.

In this tutorial we will write a simple type to work with time that does not have a date:

  1. const timeFormat = "15:04:05.999999999"
  3. type Time struct {
  4.     time.Time
  5. }

sql.Scanner

sql.ScannerCustom types - 图1open in new window assigns a value from a database driver. The value can be one of the following types:

  • int64
  • float64
  • bool
  • []byte
  • string
  • time.Time
  • nil - for NULL values
  1. var _ sql.Scanner = (*Time)(nil)
  3. // Scan scans the time parsing it if necessary using timeFormat.
  4. func (tm *Time) Scan(src interface{}) (err error) {
  5.     switch src := src.(type) {
  6.     case time.Time:
  7.         *tm = NewTime(src)
  8.         return nil
  9.     case string:
  10.         tm.Time, err = time.ParseInLocation(timeFormat, src, time.UTC)
  11.         return err
  12.     case []byte:
  13.         tm.Time, err = time.ParseInLocation(timeFormat, string(src), time.UTC)
  14.         return err
  15.     case nil:
  16.         tm.Time = time.Time{}
  17.         return nil
  18.     default:
  19.         return fmt.Errorf("unsupported data type: %T", src)
  20.     }
  21. }

You can find the full example at GitHubCustom types - 图2open in new window.

driver.Valuer

driver.ValuerCustom types - 图3open in new window returns a value for a database driver. The value must be one of the following types:

  • int64
  • float64
  • bool
  • []byte
  • string
  • time.Time
  • nil - for NULL values
  1. var _ driver.Valuer = (*Time)(nil)
  3. // Scan scans the time parsing it if necessary using timeFormat.
  4. func (tm Time) Value() (driver.Value, error) {
  5.     return tm.UTC().Format(timeFormat), nil
  6. }

You can find the full example at GitHubCustom types - 图4open in new window.

Conclusion

You can easily extend Bun with custom types to fully utilize your DBMS capabilities, for example, bunbigCustom types - 图5open in new window adds support for big.Int to Bun.

See also: