Option

Either Some(value) or None. Rust's way of saying a value might not exist.

Any value that could be absent. Replaces null from other languages.

fn find_user(id: u64)
-> Option<String>

The Option variant that contains a value. Signals the value exists.

Returning or matching when a result is present.

Some(42)
Some("Alice")
Some(wallet)

The Option variant that means no value. Rust's replacement for null.

Returning or matching when there is nothing to give back.

None // no value
// must be handled explicitly

Pulls the value out of Some. Panics if the Option is None.

Only when you are certain the value exists. Avoid in production code.

let val = option.unwrap();
// panics if None!

Checks whether an Option has a value or not. Returns bool.

The clean way to check before acting, without destructuring.

if option.is_some() {
// handle it
}
if option.is_none() { ... }

A one-pattern shortcut for match. Handles Some and ignores None.

When you only care about the value existing, and want to skip the None case.

if let Some(val) = result {
println!("{}", val);
}