迷途參照

我們現在可以瞭解 Rust 中有兩種字串型別，&str 幾近於 &[char]，但其資料是以可變長度編碼 (UTF-8) 儲存。

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}");
}

以 Rust 術語來說會是這樣：

  • &str 是對字串切片的不可變參照。
  • String 是可變動的字串緩衝區。
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 的 String 型別是位元組向量的包裝函式。就像使用 Vec<T> 一樣，該型別有專屬的擁有者。

  • 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!().

  • 您可以透過 &str 和可選的範圍選項，從 String 借用 &str 切片。如果所選位元組範圍未與字元邊界對齊，運算式會發生恐慌。比起嘗試設定正確的字元邊界，建議優先使用會對字元進行疊代的 chars 疊代器。

  • 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:

    fn main() {
    println!("{:?}", b"abc");
    println!("{:?}", &[97, 98, 99]);
}