Version: 1.0

For the complete Mojo documentation index, see llms.txt. Markdown versions of all pages are available by appending .md to any URL (e.g. /docs/manual/basics.md).

optional

Defines Optional, a type modeling a value which may or may not be present.

Optional values can be thought of as a type-safe nullable pattern. Your value can take on a value or None, and you need to check and explicitly extract the value to get it out.

Examples:

var a = Optional(1)
var b = Optional[Int](None)
if a:
    print(a.value())  # prints 1
if b:  # Bool(b) is False, so no print
    print(b.value())
var c = a.or_else(2)
var d = b.or_else(2)
print(c)  # prints 1
print(d)  # prints 2

Structs

EmptyOptionalError: An error type for when an empty Optional is accessed.
Optional: A type modeling a value which may or may not be present.
OptionalReg: A register-passable optional type.

Structs​

Structs