Rust code shared from the playground

playground.rs

#[derive(Default, Debug, Clone)]
struct Sth { pub log: Option<Log> }
#[derive(Default, Debug, Clone)]
struct Log { pub access: Option<String> }


fn main() {
    let sth = Sth { ..Default::default() };
    println!("By default, sth.log.access is not existed, because sth.log is {:?}", sth.log);
    
    let mut sth = Sth { log: Some(Log { access: Some(String::from("yes")) }) };
    // let ref_sth = &sth;
    println!("Now, `sth.log.access` is {:?}", sth.log.as_ref().unwrap().access.as_ref().unwrap());
    
    // And If you want to change the `sth.log.access` to "No", you should
    if let Some(ref mut log) = sth.log {
        if let Some(ref mut access) = log.access {
            *access = String::from("No");
        }
    }
    
    println!("Here, `sth.log.access` is {:?}", sth.log.as_ref().unwrap().access.as_ref().unwrap());
}