How to Iterate Over a String in Rust

In Rust, strings (String and &str) are UTF-8 encoded, which means characters can be multiple bytes long. This makes direct indexing impossible, but Rust provides safe and efficient ways to iterate over strings. Here’s how you can do it:

---

1. Iterate Over Characters

To iterate through each character (char) in a string:

fn main() {
    let my_string = "Hello, Rust!";
    for c in my_string.chars() {
        println!("{}", c);
    }
}

Output:

H
e
l
l
o
,

R
u
s
t
!

---

2. Iterate Over Bytes

To work with the raw bytes of a string, use the bytes method:

fn main() {
    let my_string = "Hello, Rust!";
    for b in my_string.bytes() {
        println!("{}", b);
    }
}

Output:

72
101
108
108
111
44
32
82
117
115
116
33

---

3. Iterate Over Grapheme Clusters

To handle user-perceived characters (like emojis or accented characters), use the unicode-segmentation crate:

[dependencies]
unicode-segmentation = "1.10"

use unicode_segmentation::UnicodeSegmentation;

fn main() {
    let my_string = "नमस्ते"; // Example with multi-byte characters
    for grapheme in my_string.graphemes(true) {
        println!("{}", grapheme);
    }
}

Output:

न
म
स
्
ते

---

4. Iterate with Indices

To get both the index and the character:

fn main() {
    let my_string = "Hello, Rust!";
    for (index, c) in my_string.char_indices() {
        println!("Index: {}, Character: {}", index, c);
    }
}

Output:

Index: 0, Character: H
Index: 1, Character: e
Index: 2, Character: l

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Summary

• chars: Iterate over individual characters.
• bytes: Iterate over raw bytes.
• graphemes: Work with user-perceived characters.
• char_indices: Iterate with indices.