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Puzzle 22: Explanation

Explore how asynchronous functions in Rust work by creating futures that represent tasks ready for execution. Learn the two-step process to run async functions and understand how to use await, spawn, join!, and select! for managing concurrency effectively.

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Test it out

Press “Run” to see the output of the code.

async fn hello() {
    println!("Hello, World!")
}

#[tokio::main]
pub async fn main() -> Result<(), Box<dyn std::error::Error>> {
    hello();
    Ok(())
}
Calling async functions in Rust

Explanation

Our program’s executor performs the tasks that run until they yield control back to the task queue. Tasks only yield once they return a value or error, call another asynchronous task, finish execution, or call yield_now. Tasks also don’t start when we call them. When we call a function decorated with the async keyword, it returns a future.

Calling an async decorated function doesn’t execute the function. Instead, it packages it up for future execution.

Let’s take a look at the life cycle of an asynchronous function:

  1. Create an asynchronous function, using the async keyword.
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