Understanding Self in Rust

In Rust, Self is a special type alias that refers to the type of the current trait or implementation block. It is commonly used in trait definitions and implementations to refer to the type that is implementing the trait.

trait MyTrait {
    fn new() -> Self;
    fn describe(&self) -> String;
}

struct MyStruct {
    name: String,
}

impl MyTrait for MyStruct {
    fn new() -> Self {
        Self {
            name: String::from("MyStruct"),
        }
    }

    fn describe(&self) -> String {
        format!("This is {}", self.name)
    }
}

fn main() {
    let instance = MyStruct::new();
    println!("{}", instance.describe());
}
  • The MyTrait trait defines two methods: new and describe.
  • The new method returns an instance of the type that implements the trait, denoted by Self.
  • The describe method takes a reference to self and returns a description string.
  • The MyStruct struct implements the MyTrait trait, using Self to refer to its own type within the implementation.

This allows for more flexible and reusable code, as Self can adapt to the type that is implementing the trait.