How can I convert a Vec<Option<T>> to an Option<Vec<T>>

Question

I have some vectors like this

let example1: Vec<Option<u64>> = vec![None, None, Some(2), Some(35)];
let example2: Vec<Option<u64>> = vec![Some(5), Some(19), Some(4), Some(6)];

and I want a function that would return None for example1 but would return Some([5, 19, 4, 6]) for example2.

In other words, I want a function that returns None if any of the options are None, but if all the options are Some it unwraps them all and returns Some.

Answer 1

Convert it into an iterator and use .collect::<Option<Vec<_>>>().

let output = vec.into_iter().collect::<Option<Vec<_>>>();

or using type annotations

let output: Option<Vec<_>> = vec.into_iter().collect();

See collect() and the FromIterator trait implentation it uses for Options.