Rc в Rust: Руководство по разделённому владению и RefCell

 1#[derive(Debug)]
 2struct City {
 3    name: String,
 4    history: String,
 5}
 6
 7#[derive(Debug)]
 8struct CitySummary {
 9    headline: String,
10    description: String,
11}
12
13fn main() {
14    let history = String::from("Город основан в 1574 году");
15
16    let city = City {
17        name: String::from("Уфа"),
18        history: history,
19    };
20
21    let summary = CitySummary {
22        headline: String::from("Уфа"),
23        description: history, // ❌ перемещено из-под city
24    };
25
26    println!("{:?}, {:?}", city, summary);
27}

 1use std::rc::Rc;
 2
 3#[derive(Debug)]
 4struct City {
 5    name: Rc<String>,
 6    history: Rc<String>,
 7}
 8
 9#[derive(Debug)]
10struct CitySummary {
11    headline: Rc<String>,
12    description: Rc<String>,
13}
14
15fn main() {
16    let name = Rc::new(String::from("Уфа"));
17    let history = Rc::new(String::from("Основан в 1574 году"));
18
19    let city = City {
20        name: Rc::clone(&name),
21        history: Rc::clone(&history),
22    };
23
24    let summary = CitySummary {
25        headline: Rc::clone(&name),
26        description: Rc::clone(&history),
27    };
28
29    println!("Город: {:?} Сводка: {:?}", city, summary);
30    println!("Ссылок на описание: {}", Rc::strong_count(&history));
31}
32

 1use std::rc::Rc;
 2use std::cell::RefCell;
 3
 4fn main() {
 5    let users = Rc::new(RefCell::new(vec!["Алиса".to_string()]));
 6
 7    let session1 = Rc::clone(&users);
 8    let session2 = Rc::clone(&users);
 9
10    session1.borrow_mut().push("Макс".to_string());
11    session2.borrow_mut().push("Петр".to_string());
12
13    println!("Онлайн: {:?}", users.borrow());
14}

 1#[allow(unused_variables)]
 2use std::rc::Rc;
 3use std::cell::RefCell;
 4
 5fn main() {
 6    let shared = Rc::new(RefCell::new(vec![1, 2, 3]));
 7
 8    let _first = shared.borrow_mut();
 9    let _second = shared.borrow_mut(); // ❌ паника: уже есть активный borrow_mut
10}
11

 1#[allow(unused_variables)]
 2use std::rc::Rc;
 3use std::cell::RefCell;
 4fn main() {
 5    let shared = Rc::new(RefCell::new(vec![1, 2, 3]));
 6
 7    {
 8        let mut data = shared.borrow_mut();
 9        data.push(4);
10    }
11
12    let again = shared.borrow_mut();
13    println!("{:?}", again);
14}