Module std::option

Optional values

The main type in this module Option. It can be used to represent a value that may or may not be present. An Option type can be some or none.

fn divide(a: i32, b: i32) -> Option<i32> {
    if b == 0 {
        Option::none()
    } else {
        Option::some(a / b)
    }
}

let quotient = divide(2, 1);
if quotient.is_some() {
   println!("{}", quotient.unwrap()); // unwrap panics if the value is none
}
Run this example

An Option type is useful for return values that may legitimately have no value. If an operation is expected to produce a value, but can encounter an error, it is more idiomatic to represent it with Result.

Option types can be combined in a method-chaining style using combinators such as map and and_then. They can also be unpacked with using try expressions.

Structs

Types

• type AnyOption = SameBaseAs<Option<()>>

  source

  Protocol that matches all Option types

  Example

  use std::option::AnyOption;
  
  let a = Option::some(1);
  let b: Option<i32> = Option::none();
  let c = 42;
  
  assert!(a is AnyOption);
  assert!(b is AnyOption);
  assert!(!(c is AnyOption));
  Run this example

Macros