thunky

Delay the evaluation of a paramless async function and cache the result. Adapted from mafintosh/thunky

• Documetaion
• Crates.io

Example

Let's make a simple function that returns a random number 1 second after it is called for the first time

```rust extern crate thunky; extern crate rand; use thunky::*; use rand::Rng;

fn main () { let run = move |thunk: &Thunky| { let mut rng = rand::thread_rng(); thunk.cache(Ok(rng.gen::())); };

let thunk = Thunky::new(Box::new(run));

// I miss JavaScript's `setTimeout()`
let thunk_clone = Arc::clone(&thunk);
let when = Instant::now() + Duration::from_millis(1000);
let task = Delay::new(when)
    .and_then(move |_| {
       let mut rng = rand::thread_rng();
       thunk_clone.cache(Ok(rng.gen::<u32>()));
       Ok(())
    })
    .map_err(|e| panic!("delay errored; err={:?}", e));

thunk.run(Box::new(|arg: &Result<u32, &str>| -> () {
    println!("{}", arg.unwrap()); // prints random number
}));

tokio::run(task);  

thunk.run(Box::new(|arg: &Result<u32, &str>| -> () {
    println!("{}", arg.unwrap()); // prints the same random number as above
}));

} ```

Error → No caching

If the thunk cache function is called with an Err<E>, it will not cache the result

```rust

let v = Mutex::new(0);

let run = move |thunk: &Thunky| { if *v.lock().unwrap() == 0 { thunk.cache(Err("not cache")) } else if *v.lock().unwrap() == 1 { thunk.cache(Ok(100)) } *v.lock().unwrap() += 1; }

let thunk = Thunky::new(Box::new(run));

thunk.run(Box::new(|arg: &Result| -> () { asserteq!("not cache", arg.unwraperr()); }))

thunk.run(Box::new(|arg: &Result| -> () { assert_eq!(100, arg.unwrap()); })) ```

Installation

sh cargo add thunky

License

MIT OR APACHE