Optional Arguments in Rust

optional_arguments.rs

fn say_hello(name: Option<&String>) {
  let greeting = match name {
    Some(name_str) => format!("Hello, {}!", name_str),
    None => "You don't have a name!"
  };
  println!(greeting);
}

// called like:
let name = String::from("Jeff");
say_hello(Some(&name));
// or
say_hello(None);