How to Use the Extension Trait Pattern

Use the extension trait pattern by defining a trait for a type you don't own and implementing it for that type within your own module to add new methods without modifying the original definition.

trait MyExtension {
    fn my_new_method(&self) -> String;
}

impl MyExtension for String {
    fn my_new_method(&self) -> String {
        format!("Extended: {}", self)
    }
}

fn main() {
    let s = String::from("hello");
    println!("{}", s.my_new_method());
}

The Extension Trait Pattern lets you add new features to existing code without changing the original source files. It works like adding a plugin to a software program to give it new tools without rewriting the core application. You use this when you need extra functionality for a library or standard type but cannot modify its code directly.