Rust YouTube Bits

Introduction

As I strive to improve I wanted a page for just stuff I watch on YouTube

Deref

Rust list c++ has a deference operator. You can deference with a *. But with wonderful rust you can make one. In the video from The Dev Method, they made an implementation of a box (smart pointer) and demonstrated how to do this

struct MyBox<T>(T);

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> {
        MyBox(x)
    }
}

fn main() {
    println!("Hello, world!");
    let x = 5;
    let y = MyBox::new(x);
    assert_eq!(5, x);
    assert_eq!(5, *y); // Error no deref
}

To solve this we implement the deref trait

use std::ops::Deref;

impl<T> Deref for MyBox<T> {
    type Target = T;
    fn deref(&self) -> &T {
        &self.0
    }
}

Patterns

From Let's get rust they were very keen to stress you should implement

• Debug
• Clone
• Default
• PartialEq

They also mentioned

• Send
• Sync

For the Send and Sync they suggested adding a test to make sure send, sync are implemented

fn is_normal<T: Sized + Send + Sync + Unpin>() {}
#[test]
fn is_normal_types() {
   is_normal::<User>();
}

They also mentioned implementing these where applicable and possible making in a feature to remove dependency on serde.

• Serialize
• Deserialize

Handling Option and Result and Error

This was quite a nice revisit known tricks from Code to the Moon. I never knew of these

• ok_or
• unwrap_or

General learnings are

• unwrap unwraps an Option or Result
• .ok converts between Result and Option
• .map converts to the same container but with a different type e.g.

struct MyApiError;

fn test() -> Result<i32, ParseIntError> {
    let x: i32 = "5".parse()?;
    Ok(x)
}

fn call_test() -> Result<i32, MyApiError> {
    test().map_err(|_| MyApiError)
}

Rust with Yew and Wasm

This was another video from Code to the Moon and demonstrated using rust as a front-end using yew [[1]]. Not sure it will catch on. No release last year 2024. You need to cargo install trunk and here is the code from [Code to the Moon], here to show how easy it was

use yew::prelude::*;

struct Model {
    value: i64
}

#[function_component(App)]
fn app() -> Html {
    let state = use_state(|| Model {
        value: 0
    });

    let onclick = {
        let state = state.clone();

        Callback::from(move |_| {
            state.set(Model {
                value: state.value + 1
            })
        })
    };

    html! {
        <div>
            <button {onclick}>
                { "+1" }
            </button>
            <p>{ state.value }</p>
        </div>
    }
}

fn main() {
    yew::start_app::<App>();
}