null

null is a package for providing types to handle nullable values.

For a comparable type V, the nullable type null.T[V] implements sql.Scanner and json.Unmarshaler. It can be used with types such as:

Named integer types like time.Duration
Structs with comparable fields
Arrays consisting of comparable elements

null.T is oriented towards immutability. Therefore, unlike sql.NullInt64, null.T does not have APIs for modification.

null.T does not expose its fields.
null.T does not have methods for modification (excluding Scan and Unmarshal).

func main() {
	var d null.T[time.Duration]

	// "null" -> null
	json.Unmarshal([]byte(`null`), &d)
	fmt.Printf("valid: %v, value: %v\n", !d.IsNull(), d.ValueOrZero())
	// Output:
	// valid: false, value: 0s

	// "0" -> "0s" (zero value, not null)
	json.Unmarshal([]byte(`0`), &d)
	fmt.Printf("valid: %v, value: %v\n", !d.IsNull(), d.ValueOrZero())
	// Output:
	// valid: true, value: 0s

	// nil -> null
	d.Scan(nil)
	fmt.Printf("valid: %v, value: %v\n", !d.IsNull(), d.ValueOrZero())
	// Output:
	// valid: false, value: 0s
}

Differences from gopkg.in/guregu/null

Differences from the well-known package gopkg.in/guregu/null, which also defines nullable types include:

Generics: null supports not only bool, int64, float64, string, and time.Time, but also any comparable type.
Immutablity: null.T does not have APIs for modification.
- null.T does not expose its fields.
- null.T does not have a SetValid method.
Fewer APIs: This package does not provide several APIs defined in guregu/null.
- New*
- MarshalText, UnmarshalText
- SetValid

Minor differences

guregu/null.Int can json-unmarshal quoted numbers like "123", but null.T[int64] cannot. This aligns with the behavior when json.Unmarshal is applied to int64.
guregu/null.Float can json-unmarshal quoted numbers like "1.23", but null.T[float64] cannot. This aligns with the behavior when json.Unmarshal is applied to float64.
For floats with extremely small or large absolute values, the output of MarshalJSON for guregu/null.Float and null.T[float64] is different. null.T[float64] matches the behavior when float64 is passed to json.MarshalJSON.
The method IsZero has been renamed to IsNull.

qawatake/null

null

Differences from gopkg.in/guregu/null

Minor differences