# Closures in Rust

## Capturing only select variables

fn closures() {
    let mut a = 10;
    let b = Box::new(20);
    let handle = |ab: &mut i32, b| {
        println!("{:?}", b);
        *ab += 10;
        println!("Hello from a thread - {}", ab);
    }; 
    handle(&mut a, b); // mutable borrow of a, move the box
    println!("{}", a)

}

## Capturing all variables in closure

**only variables that were used are captured**

    fn closures() { 
        let mut a = 10;
        let mut b = Box::new(20); // create a mut box
        let r = b.as_mut(); // create a mutable ref, to pass to closure, only one mutable reference
        let c = Box::new(300);
        let ref_c = c.as_ref(); // or &c remember to pass only reference to closure for using later
        let mut handle = move || { // you should create references beforehand, if you want to pass as reference and use them later
            *r += 30; // only the mutable ref is moved here, b is fine outside chilling, can be used
            a += 20; 
            println!("Hello from a closure - {}", a);
            println!("Immutable box borrowed as ref - {}", *ref_c)
        }; 
        handle();
        println!("{}", a); // a is 10, because a implements Copy, and that Copy is moved into closure
        println!("{}", b);
        println!("Immutable box {}", c);
    
    }