Smart Pointers

Rc

Shared Read-Only Ownership

Rc<T> lets several owners point to the same immutable value in single-threaded code.

Program

Play the program to clone Rc handles and watch the shared owner count grow.

rc_shared_owner.rs 
use std::rc::Rc;

fn main() {
    let label = ;
    let shared = Rc::new(String::from(label));
    let first = Rc::clone(&shared);
    let second = Rc::clone(&shared);
    let count = Rc::strong_count(&shared);
    println!("{} {count}", first);
}

use std::rc::Rc;

fn main() {
    let label = ;
    let shared = Rc::new(String::from(label));
    let first = Rc::clone(&shared);
    let second = Rc::clone(&shared);
    let count = Rc::strong_count(&shared);
    println!("{} {count}", first);
}

use std::rc::Rc;

fn main() {
    let label = ;
    let shared = Rc::new(String::from(label));
    let first = Rc::clone(&shared);
    let second = Rc::clone(&shared);
    let count = Rc::strong_count(&shared);
    println!("{} {count}", first);
}
Rc<T> `Rc<T>` is a reference-counted smart pointer for shared ownership.
Rc::clone `Rc::clone` creates another owner of the same allocation.
strong_count `Rc::strong_count` reports how many owners currently exist.