How to handle may panic if I know it is imposible to panic in rust-CodePudding

I have a error on the first parsing: may panic if the index is out of bounds. But the if before parsing shoud handle this. How to handle the error correctly?

print!("Write 2 ints separated by space: ");
let mut nums_string: String = String::new();
stdout().flush().expect(ERR_MSG_STDOUT_FLUSH);
stdin()
    .read_line(&mut nums_string)
    .expect(ERR_MSG_STDIN_READ_LINE);
let nums_str_vec: Vec<&str> = nums_string.trim().split(' ').collect();
let num1: i32;
let num2: i32;
if nums_str_vec.len() == 2 {
    num1 = match nums_str_vec[0].parse() {
        Err(_) => panic!("Wrong input"),
        Ok(_) => nums_str_vec[0].parse().unwrap(),
    };
    num2 = match nums_str_vec[1].parse() {
        Err(_) => panic!("Wrong input"),
        Ok(_) => nums_str_vec[1].parse().unwrap(),
    };
} else {
    panic!("Wrong input");
}

Is possible to handle error without if and use only the match?

CodePudding user response：

The solution for handling "may panic" if you know it won't panic is to not repeat the code that may panic.

If you have already determined that it is a number by matching the Ok case, you do not need to parse it again.

The number is contained in the Ok value, which you currently ignore. Use it!

Ok(n) => n,

CodePudding user response：

Is possible to handle error without if and use only the match?

Complemeting mkrieger1's answer, a few additional transformations before the vec will give you a much simpler match thanks to slice patterns:

let nums: Vec<Result<i32, _>> = nums_string.trim().split_whitespace().map(str::parse).collect();
match nums[..] {
    [Ok(n1), Ok(n2)] => println!("{} {}", n1, n2),
    _ => println!("Wrong input"),
}