Function scoped::scoped

pub fn scoped<'a, R: Failure>(scope: impl FnOnce(&Guard<'a>) -> R + 'a) -> R

Executes the scope scope. A scope is a closure, in which access to a guard is granted. A guard is used to schedule callbacks to run on a scope’s success, failure, or exit.

For more information on how to use the guard, see Guard.

The scope is required to return a type implementing Failure, to indicate whether the scoped exited with success, or failure.

Examples

use scoped::{Guard, scoped};

fn main() {
    use std::cell::Cell;

    let mut n = Cell::new(0);

    scoped(|guard| -> Result<(), ()> {

        guard.on_scope_exit(|| {
            assert_eq!(n.get(), 2);
            n.set(3);
        });

        guard.on_scope_success(|| {
            assert_eq!(n.get(), 1);
            n.set(2);
        });

        n.set(1);
        Ok(())
    });
    assert_eq!(n.get(), 3);
}

A callback can also be cancelled, using Handle::cancel

use scoped::{Guard, scoped};

fn main() {

    let mut v = vec![1, 2, 3];

    scoped(|guard| -> Option<()> {
        let mut handle = guard.on_scope_exit_with(&mut v, |vec| {
            panic!()
        });

        handle.push(4);
         
        let cancelled = handle.cancel();

        cancelled.push(5);
         
        Some(())
    });

    assert_eq!(v, vec![1, 2, 3, 4, 5]);
}