Slice Type

Another data type that does not have ownership is the slice. Slices let you reference a contiguous sequence of elements in a collection rather than the whole collection.

Slicing an String

let s = String::from("Hello, world");

let hello = &s[0..5];

1. If the initial range index is 0(i.e. first index), it could be omitted.

2. If the last range index is 0(i.e. last index), it could be omitted as well.

For example: &s[..] would reference the whole string("Hello, world"), instead of referencing a part of it.

In Rust, .. is called as range syntax.

A program to return first word from given string:

fn main() {
  let s = String::from("Hello, world");

  let word = get_first_word(&s);

  s.clear();  // this line would throw error as it
              // was borrowed as immutable before
}


fn get_first_word(s: &str) -> &str {
  let str_bytes = s.as_bytes();

  for (i, &item) in str_bytes.iter().enumerate() {
    if item == b' ' {
      return &s[0..i];
    }
  }

  return &s[..];
}

Note: When a parameter is declared as type slice, it would be able to accept type String as well as type Slice. But type String can't accept type Slice.