How to Iterate Over a String by Character in Rust

Using chars Method

The chars() method returns an iterator over the chars of a string slice. See the following example:

fn main() {
  let s = "abc";

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

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

a
b
c
0 a
1 b
2 c

Using Vec

You could also create a vector of chars and work on it from there, but that's more time and space intensive:

fn main() {
  let s = "abc";

  let v: Vec<_> = s.chars().collect();
  println!("{:?}", v);
}

['a', 'b', 'c']

It’s important to remember that char represents a Unicode Scalar Value, and might not match your idea of what a ‘character’ is. Iteration over grapheme clusters may be what you actually want.

Using unicode-segmentation

Installation

This crate is fully compatible with Cargo. Just add it to your Cargo.toml:

[dependencies]
unicode-segmentation = "1"

unicode-segmentation Usage

use unicode_segmentation::UnicodeSegmentation;

fn main() {
  let s = "a̐";

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

  // UnicodeSegmentation
  for g in s.graphemes(true) {
    println!("{:?}", g);
  }
}

'a'
'\u{310}'
"a\u{310}"

Rust Compile Errors

no method named `graphemes` found for reference `&str` in the current scope :

// use unicode_segmentation::UnicodeSegmentation;
for g in s.graphemes(true) {

error[E0599]: no method named `graphemes` found for reference `&str` in the current scope
 --> src/main.rs:5:14
  |
5 |   for g in s.graphemes(true) {
  |              ^^^^^^^^^ method not found in `&str`