test.rs

use std::rc::Rc;
use std::cell::RefCell;
use std::ops::DerefMut;

struct A<'a> {
    pub v: Vec<Rc<RefCell<FnMut() + 'a>>>,
}
impl<'a> A<'a> {
    pub fn add3<F: FnMut() + 'a>(&mut self, f: F) {
        let r = Rc::new(RefCell::new(f));
        self.v.push(r.clone());
        self.v.push(r.clone());
        self.v.push(r.clone());
    }

    pub fn run(&mut self) {
        for f in &mut self.v {
            f.borrow_mut().deref_mut()();
        }
    }
}

fn main() {
    let mut s = String::new();
    {
        let mut a = A { v: Vec::new() };
        a.add3(|| {
            s.push_str("foo");
        });
        a.run();
    }

    println!("{}", s); // "foofoofoo"
}