Mastering Rust - Second Edition

Mutating shared data from threads

We'll take a look at a sample program where five threads push data to a shared Vec. The following program tries to do the same:

// thread_mut.rsuse std::thread;use std::sync::Arc;fn main() {    let mut nums = Arc::new(vec![]);    for n in 0..5 {        let mut ns = nums.clone();        thread::spawn(move || {            nums.push(n);        });    }}

We have the same nums wrapped with Arc. But we cannot mutate it, as the compiler gives the following error:

This doesn't work as cloning Arc hands out immutable reference to the inner value. To mutate data from multiple threads, we need to use a type that provides shared mutability just like RefCell ...