Shared State Patterns

Cell Attempt Counter

Update a Copy Value

Cell<T> supports interior mutation for small copyable values without taking a mutable reference.

Program

Play the program to choose how many attempts update the shared counter.

cell_attempt_counter.rs 
use std::cell::Cell;

fn main() {
    let retries = ;
    let attempts = Cell::new(0);
    for _ in 0..retries {
        attempts.set(attempts.get() + 1);
    }
    println!("attempts={}", attempts.get());
}

use std::cell::Cell;

fn main() {
    let retries = ;
    let attempts = Cell::new(0);
    for _ in 0..retries {
        attempts.set(attempts.get() + 1);
    }
    println!("attempts={}", attempts.get());
}

use std::cell::Cell;

fn main() {
    let retries = ;
    let attempts = Cell::new(0);
    for _ in 0..retries {
        attempts.set(attempts.get() + 1);
    }
    println!("attempts={}", attempts.get());
}
Cell `Cell` lets code replace a copyable value even through a shared binding.
get `get` reads the current copy of the value.
set `set` writes a replacement value back into the cell.