async fn subtask() {
println!("> > subtask"); (4)
}
async fn task() {
println!("> Before subtask"); (3)
subtask().await;
println!("> After subtask"); (5)
}
fn main() {
futures::executor::block_on(async {
println!("before future"); (1)
let future = task();
println!("future is created"); (2)
future.await;
println!("future is awaited"); (6)
});
}Async Await
Laziness in Detail
Example: JavaScript
Rust Futures vs JavaScript Promises
Eager Execution (JavaScript and many other languages)
async function subtask() {
console.log("> > subtask"); (3)
}
async function task() {
console.log("> before subtask"); (2)
await subtask();
console.log("> after subtask"); (5)
}
(async function main() {
console.log("before promise"); (1)
let promise = task();
console.log("promise is created"); (4)
await promise;
console.log("promise is awaited"); (6)
})();
Eager Execution (JavaScript and many other languages)
Eager Execution: Takeaways
Lazy Execution: Rust Futures
async fn subtask() {
println!("> > subtask"); (4)
}
async fn task() {
println!("> Before subtask"); (3)
subtask().await;
println!("> After subtask"); (5)
}
fn main() {
futures::executor::block_on(async {
println!("before future"); (1)
let future = task();
println!("future is created"); (2)
future.await;
println!("future is awaited"); (6)
});
}