Cell Types

Interior mutability without runtime borrow checking

Cell

use std::cell::Cell;

fn main() {
    // Cell - for Copy types
    let cell = Cell::new(42);

    println!("=== Cell ===");
    println!("Initial: {}", cell.get());

    // Set value
    cell.set(100);
    println!("After set: {}", cell.get());

    // Replace and get old
    let old = cell.replace(200);
    println!("Replaced {} with 200", old);
    println!("Current: {}", cell.get());

    // Swap
    let other = Cell::new(999);
    cell.swap(&other);
    println!("\nAfter swap:");
    println!("cell: {}", cell.get());
    println!("other: {}", other.get());

    // Take - replaces with Default
    let taken = cell.take();
    println!("\nTaken: {}", taken);
    println!("After take: {}", cell.get());

    // In struct (common pattern)
    struct Counter {
        count: Cell<i32>,
    }

    let counter = Counter { count: Cell::new(0) };
    counter.count.set(counter.count.get() + 1);
    counter.count.set(counter.count.get() + 1);
    println!("\nCounter: {}", counter.count.get());
}