The Rust Programming Language 日本語版 メモ

戻り値とスコープ

fn main() {
  let s1 = gives_ownership();

  print!("{}", s1); // hello

  let s2 = String::from("hello");

  let s3 = takes_and_gives_back(s2);
  print!("{}", s3); // hello

  // error[E0382]: borrow of moved value: `s2`
  print!("{}", s2);
}

fn gives_ownership() -> String {
  let some_string = String::from("hello");
  some_string
}

fn takes_and_gives_back(a_string: String) -> String {
  a_string
}

fn main() {
    let s1 = String::from("hello");

    let (s2, len) = calculate_length(s1);

    // The length of 'hello' is 5.
    println!("The length of '{}' is {}.", s2, len);
}

fn calculate_length(s: String) -> (String, usize) {
    let length = s.len();

    (s, length)
}

fn main() {
  let s1 = String::from("hello");

  // error[E0308]: mismatched types
  let len = calculate_length(s1);

  println!("The length of '{}' is {}.", s1, len);
}

fn calculate_length(s: &String) -> usize {
  s.len()
}

fn main() {
    let s1 = String::from("hello");

    let len = calculate_length(&s1);

    // The length of 'hello' is 5.
    println!("The length of '{}' is {}.", s1, len);
}

fn calculate_length(s: &String) -> usize {
    s.len()
}