How to parse an empty string into a None?

Question

What is the idiomatic way to handle the parsing of an empty string into a None and not a Some("")?

let handle: Option<String> = x.get(0).and_then(|v| v.parse().ok());

Answer 1

If you start with a String:

let string = String::new();
let handle = Some(string).filter(|s| !s.is_empty());

Since Rust 1.50 you can also use bool::then (thanks sebpuetz)

let handle = string.is_empty().not().then(|| string);
// or
let handle = (!string.is_empty()).then(|| string);

With your code:

let handle = x.get(0)
    .and_then(|v| v.parse().ok())
    .filter(String::is_empty);

Docs

• String::is_empty
• Option::filter
• bool::then