Option enum

Ref - https://viblo.asia/p/billion-dollar-mistake-RQqKLopr57z

The Option enum was introduced in Rust to handle the concept of nullability in a safe and expressive way. Unlike many programming languages that use a null or similar keyword to represent the absence of a value, Rust doesn’t have null.

pub enum Option<T> {
    None,
    Some(T),
}

If you ever have a function that should return null, return an Option instead.

For example

fn find_first_a(s: String) -> Option<i32> {
    for (index, character) in s.chars().enumerate() {
        if character == 'a' {
            return Some(index as i32);
        }
    }
    return None;
}

fn main() {
    let my_string = String::from("raman");
    match find_first_a(my_string) {
        Some(index) => println!("The letter 'a' is found at index: {}", index),
        None => println!("The letter 'a' is not found in the string."),
    }
}