字符串

现在我们就可以理解 Rust 中的两种字符串类型：

  • &str is a slice of UTF-8 encoded bytes, similar to &[u8].
  • String is an owned, heap-allocated buffer of UTF-8 bytes.
1. fn main() {
2. let s1: &str = "World";
3. println!("s1: {s1}");

5. let mut s2: String = String::from("Hello ");
6. println!("s2: {s2}");
7. s2.push_str(s1);
8. println!("s2: {s2}");

10. let s3: &str = &s2[s2.len() - s1.len()..];
11. println!("s3: {s3}");
12. }

This slide should take about 10 minutes.

  • &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 push() and push_str() methods.
  • The format!() macro is a convenient way to generate an owned string from dynamic values. It accepts the same format specification as println!().
  • You can borrow &str slices from String via & and optionally range selection. If you select a byte range that is not aligned to character boundaries, the expression will panic. The chars iterator iterates over characters and is preferred over trying to get character boundaries right.
  • For C++ programmers: think of &str as std::string_view 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).
  • Byte strings literals allow you to create a &[u8] value directly:

1. fn main() { 2. println!("{:?}", b"abc"); 3. println!("{:?}", &[97, 98, 99]); 4. } - 原始字符串可在创建 &str 时禁用转义：r"\n" == "\\n"。可以在外层引号两侧添加相同数量的 #，以在字符串中嵌入双引号：

1. fn main() { 2. println!(r#"<a href="link.html">link</a>"#); 3. println!("<a href=\"link.html\">link</a>"); 4. }