From and Into are great

July 11, 2021

Rust’s From and Into traits are great.
Once you implemented one of them, they allow you to convert between two types simply by calling either Target::from(source) or source.into().
In previous posts you might have noticed the deeply nested constructions of Items such as:

fn offer(&mut self, _pos: &PosRelative) -> Option<Item> {
        .map(|x| Item::Material(Material::Plate(x)))

This is caused due to the definition of the Item type:

pub enum Item {

pub enum Material {

pub enum Plate {

To e.g. construct an Item from a Plate one has to also mention the intermediate Material type.
This is quite annoying to type and reduces the readability of the code.
But once the From conversion is implemented:

impl From<Plate> for Item {
    fn from(x: Plate) -> Self {

The previously long construction can be simplified to a single .into() call:

fn offer(&mut self, _pos: &PosRelative) -> Option<Item> {
    self.product.take().map(|x| x.into())

Due to the many conversions within Combine And Conquer from specific types such as Plate to more generic ones such as Material or even Item, using From or Into is incredibly helpful.