Code shared from the Rust Playground

playground.rs

#![feature(futures_api)]

extern crate futures; // 0.1.25
use futures::prelude::*;
use futures::future::{ok};

pub struct Boop {}

pub enum Cmd {
    A,
    B
}

impl Boop {
    pub fn a(&mut self, ) -> impl Future<Item=(), Error=()> {
        ok(())
    }
    
    pub fn b(&mut self, ) -> impl Future<Item=(), Error=()> {
        ok(())
    }
    
    pub async fn c(&mut self, ) -> Result<(), ()> {
        Ok(())
    }
    
    pub fn exec(&mut self, cmd: Cmd) -> impl Future<Item=(), Error=()> {
        match cmd {
            Cmd::A => self.a(),
            Cmd::B => self.b(),
        }
    }
}



fn main() {
    let mut b = Boop{};
    
    b.a().wait().unwrap();
    b.b().wait().unwrap();
    b.exec(Cmd::A).wait().unwrap();
    b.exec(Cmd::B).wait().unwrap();
}