Rust Notes — Module 4

Sat, 21 Mar 2026 00:00:00 +0000

Rust Notes — Module 4: Traits

1. What is a Trait?

A trait defines a set of behaviors (methods) that a type must implement. It is a contract — any type that implements the trait promises to provide those behaviors.

trait Greet {
 fn hello(&self) -> String;
}

Concept	Rust	C++	Go
Trait	`trait`	abstract class / concept	interface
Implementation	`impl Trait for Type`	override virtual method	implicit (duck typing)
Dispatch	static (default) or dynamic	virtual table	interface table

2. Implementing a Trait

struct Human { name: String }
struct Robot { id: u32 }

impl Greet for Human {
 fn hello(&self) -> String {
 format!("Hi, I'm {}!", self.name)
 }
}

impl Greet for Robot {
 fn hello(&self) -> String {
 format!("BEEP. I AM UNIT {}.", self.id)
 }
}

Each type provides its own implementation of the trait methods.
A type can implement any number of traits.
You can implement traits for types you didn’t define (with some restrictions — see orphan rule below).

3. Default Implementations

Traits can provide default method implementations. Types can override them or inherit them for free:

Traits on Sanketh's Blog

Rust Notes — Module 4

Rust Notes — Module 4: Traits

1. What is a Trait?

2. Implementing a Trait

3. Default Implementations