You can iterate over the characters in a Rust String using a for loop and calling the .chars() method on the String. Here's an example:

rust iterate over string

let s = "Hello, world!".to_string();

for c in s.chars() {
    println!("{}", c);
}

This will print each character in the string on a separate line.

You can also use the .bytes() method to iterate over the bytes in a String, or the .enumerate() method to get both the index and the character at each position in the string.

for (i, c) in s.chars().enumerate() {
    println!("{}: {}", i, c);
}

This will print the index and character for each position in the string, like this:

0: H
1: e
2: l
3: l
4: o
5: ,
6:  
7: w
8: o
9: r
10: l
11: d
12: !