Rust 101 – 36: What async and await really do

Attempting to explain as slowly as possible what actually happens when the compiler finds an async function containing awaits: it writes a poll method for you to create something that implements Future. The generated poll method polls the Futures you asked to await, in order. The interesting bit is that this generated thing that implements Future and has a poll method needs to own the things it refers to, which is what leads to some of the most confusing error messages you see when writing this kind of code.

Series: Language basics, More syntax, Traits and generics, Building applications, Concurrency and parallelism, Trait objects, Async, Unsafe

This section (Async): 34: What is async?, 35: Futures, 36: async/await, 37: Runtimes, 38: Exercise E1a, 39: Exercise E1b, 40: Exercise E2a, 41: Exercise E2b

Links:

• Slides: Rust 101 – module E
• Exercises: artificialworlds.net/presentations/rust-101/exercises/E-async-web/mod.html

The course materials for this series are developed by tweede golf. You can find more information at github.com/tweedegolf/101-rs and you can sponsor the work at github.com/sponsors/tweedegolf. They are released under the Creative Commons Attribution Share Alike 4.0 International license.

This series of videos is copyright 2024 Andy Balaam and the tweede golf contributors and is released under the Creative Commons Attribution Share Alike 4.0 International license.