rust - 如何将单个字符 String 转换为 char？

Question

这个问题看似微不足道，但我找不到答案。假设 letter 是单个字符串，我如何将 letter 转换为 char？

let mut letter = String::new();

io::stdin()
    .read_line(&mut letter)
    .expect("Failed to read line");

Answer 1

一种解决方案是使用 chars method .这将返回字符串切片的 char 上的迭代器。

let letter_as_char: char = letter.chars().next().unwrap();
println!("{:?}", letter_as_char);

但它是important to remember that

char represents a Unicode Scalar Value, and might not match your ideaof what a ‘character’ is. Iteration over grapheme clusters may be whatyou actually want. For example, Consider the String H

let y = "H";

let mut chars = y.chars();

assert_eq!(Some('H'), chars.next());   
assert_eq!(None, chars.next());

Now consider "y̆"

let y = "y̆";

let mut chars = y.chars();

assert_eq!(Some('y'), chars.next()); // not 'y̆'
assert_eq!(Some('\u{0306}'), chars.next());

assert_eq!(None, chars.next());

另见:

• How to iterate over Unicode grapheme clusters in Rust?