use std::sync::{Arc, Mutex};

struct Foo {
    listeners : Vec<Arc<Mutex<FnMut() + Send>>>
}

impl Foo {
    fn new() -> Self {
        Foo {
            listeners: Vec::new()
        }
    }
    fn call_funcs(&mut self) {
        for f in &self.listeners {
            let mut f = f.lock().unwrap();
            let f = &mut *f;
            f();
        }
    }
}

fn main() {
    let mut foo = Foo::new();
    foo.call_funcs();

    println!("{:?}", 5);
}