mirror of https://github.com/google/comprehensive-rust.git synced 2025-05-16 23:55:42 +02:00

* Update string-slices.md

* Adding an extra example of converting `String` back to `&str`.
* C++ who would often read this guide could get immediate intuitive understanding of Rust strings if you compare them to C++ equivalents.

* Expand on `String` vs `std::string`

Co-authored-by: Martin Geisler <martin@geisler.net>

2023-01-24 08:52:55 +00:00

1.4 KiB

Raw Blame History

`String` vs `str`

We can now understand the two string types in Rust:

fn main() {
    let s1: &str = "World";
    println!("s1: {s1}");

    let mut s2: String = String::from("Hello ");
    println!("s2: {s2}");
    s2.push_str(s1);
    println!("s2: {s2}");
    
    let s3: &str = &s2[6..];
    println!("s3: {s3}");
}

Rust terminology:

&str an immutable reference to a string slice.
String a mutable string buffer.

&str introduces a string slice, which is an immutable reference to UTF-8 encoded string data stored in a block of memory. String literals (”Hello”), are stored in the program’s binary.
Rust’s String type is a wrapper around a vector of bytes. As with a Vec<T>, it is owned.
As with many other types
String::from creates a string from a string literal; String::new creates a new empty string, to which string data can be added using the to_string method.
The push_str method appends a string slice to the string.
You can borrow &str slices from String via & and optionally range selection.
For C++ programmers: think of &str as const char* from C++, but the one that always points to a valid string in memory. Rust String is a rough equivalent of std::string from C++ (main difference: it can only contain UTF-8 encoded bytes and will never use a small-string optimization).

1.4 KiB Raw Blame History

String vs str

1.4 KiB

Raw Blame History

`String` vs `str`