Rust Programming Cookbook

How to do it...

In a few quick steps, you'll know how to move between Option and Result:

1. Create a new project with cargo new options-results --lib and open it with VS Code.
2. Let's edit src/lib.rs and replace the existing test (inside mod tests) with the following:

    #[derive(Debug, Eq, PartialEq, Copy, Clone)]    struct MyError;    #[test]    fn transposing() {        // code will follow    }

3. We have to replace // code will follow with an example of how to use the transpose() function:

        let this: Result<Option<i32>, MyError> = Ok(Some(42));        let other: Option<Result<i32, MyError>> = Some(Ok(42));        assert_eq!(this, other.transpose());

4. This works with Err as well and, for proof, add this to the transpose() test:

 let this: Result<Option<i32>, MyError> = Err(MyError); ...