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【转】rust中impl关键字的用法---What is the Impl keyword in Rust?

原文：https://www.educative.io/edpresso/what-is-the-impl-keyword-in-rust

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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:

Inherent implementations
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();
}