how to convert Option<&u8> to u8

July 16, 2022

i want to convert Option<&u8> to u8 so i will be able to print it

my code:

fn main() {
    let v : Vec<u8> = vec![1, 2, 3, 4, 5];

    let out_of_range = &v[100];
    let out_of_range = v.get(100);
    match out_of_range{
        Some(&u8) => println!("data out of range: {}", out_of_range),
        None => println!("bruh"),
    }
}

>Solution :

Your match statement needs the introduction of a binding, not a type (the &u8 you used was not expected here).

Here Some(val) matches with something which is an Option<&u8>, thus val is a binding to the embedded &u8 (if not None, of course).

The example explicitly dereferences val as an illustration, and highlights the fact that val is not an u8 but a reference, but it’s not required for the following operation (printing).

fn main() {
    let v: Vec<u8> = vec![1, 2, 3, 4, 5];
    for idx in [2, 20, 4] {
        let at_index = v.get(idx);
        match at_index {
            Some(val) => {
                // val has type &u8
                let copy_of_val = *val; // not required, just for the example
                println!("at {} --> {}", idx, copy_of_val);
            }
            None => println!("no value at {}", idx),
        }
    }
}