Why do I need to use & in this code example

I’m a new user of Rust and I am following the experimental book to learn it. I have read this chapter: https://rust-book.cs.brown.edu/ch04-04-slices.html, where they propose the following code:

    fn first_word(s: &String) -> usize {
        let bytes = s.as_bytes();
    
        for (i, &item) in bytes.iter().enumerate() {
            if item == b' ' {
                return i;
            }
        }
    
        s.len()
    }

My doubt is about &item, they say:

"Because we get a reference to the element from .iter().enumerate(), we use & in the pattern."

If that’s the case, then why do they use item like item == b' '. From my understanding, if item is a reference, then I would need to access the value the reference is pointing to, something like *item == b' '.

Could someone explain to me the difference? Sorry if it’s a trivial question.

>Solution :

b' ' is a u8. It’s not a reference, just an ordinary, everyday scalar. Without any dereferences, if we write

for (i, item) in bytes.iter().enumerate() {

then item is a &u8, since we’re borrowing from the underlying iterator. We can’t compare a &u8 to a u8, so we need to deref. We can deref at the call site

if *item == b' '

or in the pattern

for (i, &item) in bytes.iter().enumerate()

but not both. It’s your call how you deref, but you have to get rid of the reference somehow.