Future and async/await are the mechanism in Rust to simplify writing concurrent programs. But it seems to be hard to understand. In this article, I will introduce my intuitive understanding of Future and async/await in Rust.

In this tutorial, I'll go through the process of building a telegram bot in Rust, hosted in Azure Function. As an example, we build a bot to randomly pick a line from the message to help you, for example, decide what to eat for dinner.

WARNING: This may be a bad practice. The point of this article is just to share my idea.

Exception is a popular feature in many programming languages. Unlike Rust where errors are considered as a return value of the Err case of Result, in these languages errors are thrown like panic. The caller may catch the errors and process them similar to catch_unwind in Rust. Different people may have different preferences on the error handling style, but panic-unwind is always considered a bad practice and should be avoided if possible. So using exception-like error handling in Rust is impossible.

Well, it is possible with async Rust, but we need a little trick. The main idea here is to stop polling the future after an exception is thrown.

I love the traits in Rust language. Rust uses one mechanism for both compile-time polymorphism and runtime polymorphism, which is elegant. However, the runtime polymorphism in Rust is not very flexible. Some traits cannot be used as a trait object, and it's impossible to specify whether a method is resolved dynamically or statically. This shortage is reflected in my recursive function library RecurFn, and I develop a workaround, calling it customized trait object.