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What is the Impl keyword in Rust?

Anusheh Zohair Mustafeez

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

The impl keyword in Rust is used to implement some functionality on types. This functionality can include both functions and costs. There are two main kinds of implementations in Rust:

  1. Inherent implementations
  2. Trait implementations

In this shot, we will focus on inherent implementations. You can learn more about trait implementations here.

Inherent implementations, as the name implies, are standalone. They are tied to a single concrete self type that is specified after the impl keyword. These implementations, unlike standard functions, are always in scope.

Code

In the following program, we are adding methods to a Person struct with the impl keyword:

struct Person {
name: String,
age: u32
}
// Implementing functionality on the Person struct with the impl keyword
impl Person{
// This method is used to introduce a person
fn introduction(&self){
println!("Hello! My name is {} and I am {} years old.", self.name, self.age);
}
// This method updates the age of the person on their birthday
fn birthday(&mut self){
self.age = self.age + 1
}
}
fn main() {
// Instantiating a mutable Person object
let mut person = Person{name: "Hania".to_string(), age: 23};
// person introduces themself before their birthday
println!("Introduction before birthday:");
person.introduction();
// person ages one year on their birthday
person.birthday();
// person introduces themself after their birthday
println!("\nIntroduction after birthday:");
person.introduction();
}

RELATED TAGS

rust
implementation
inherent
trait

CONTRIBUTOR

Anusheh Zohair Mustafeez
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Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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