options.md

Options

Option<T> is an enum that is generic over type T and has two variants: Some, which holds one value of type T, and a None variant that doesn’t hold any value.

enum Option<T> {
    Some(T),
    None,
}

Option<T> has a number of uses:

• Initial values
• Return values for functions that are not defined over their entire input range (partial functions)
• Return value for otherwise reporting simple errors, where None is returned on error
• Optional struct fields
• Struct fields that can be loaned or "taken"
• Optional function arguments
• Nullable pointers
• Swapping things out of difficult situations