The Rust Slice Type

Slice is a kind of data structure that store heap memory, it contains two fields, one representing the memory address and the other representing the length. Our most common string literal is a kind of slice.

Slice let us reference a contiguous sequence of elements in a collection rather than the whole collection. A slice is a kind of reference, so it does not have ownership. And the slice ensures that the data it references is always valid.

String Slices

A string slice is a reference to part of a String, and it looks like this:

let s = String::from("hello world");
let world = &s[6..11];

The s is a reference to the entire String hello world, but the world is a slice, it reference to part of the String hello world. String slice referring to part of a String

We can use slices to refer to any part of a string with Rust’s ..syntax, for example:

let s = String::from("hello world");
let world = &s[6..11];    ==> "world"
let s1 = &s[3..];     ==> "lo world"
let s2 = &s[..];      ==> "hello world"
let s3 = &s[..2];      ==> "he"

The string slice type is represented by &str, it can be used as a function return type, for example:

fn first_world(s:&String) -> &str {
    &s[..]
}

Other Slices

In addition to string slicing, there are other collection slicing types, such as array slicing.

let a:[i8;4]=[2, 3, 4, 5];     ==> &[i8]
let slice = &a[1..3];