Combining futures

Combining, and chaining, our futures allows us to perform multiple operations in sequential order and helps organize our code a bit more. They can be used to transform, splice, filter, and so on <Self as Future>::Items. 

How to do it...

1. Inside the bin folder, create a new file called combinators.rs.

 

2. Add the following code and run it with cargo run --bin combinators:

1   extern crate futures;
2   extern crate futures_util;
3   
4   use futures::prelude::*;
5   use futures::channel::{mpsc, oneshot};
6   use futures::executor::block_on;
7   use futures::future::{ok, err, join_all, select_all, poll_fn};
8   use futures::stream::iter_result;
9   use futures_util::stream::select_all as select_all_stream;
10  
11  use std::thread;
12  
13  const FINISHED: Result<Async<()>, Never> = Ok(Async::Ready(()));

3. Let's add our join_all example function:

15  fn join_all_example() {
16    let future1 = Ok::<_, ()>(vec![1, 2, 3]);
17    let future2 = Ok(vec![10, 20, 30]...