Strings in Rust in Rust

The Rust string is an object that represents a sequence of characters, each identified by one index.

Creation:

To create strings in Rust, you use double quotes like this:

let greeting = "Hello";

Accessing characters:

To access the characters in a string, you use the .chars().nth() method

The following example returns the first character of a string with the index zero:

let str = "Hello";
let ch = str.chars().nth(0).unwrap();
// ch is 'H'

Getting the length:

We can get the length of a string using the .len() method.

For example, to access the last character of the string, you use the .chars().last() method:

let str = "Hello";
let ch = str.chars().last().unwrap();
// ch is 'o'

Concatenating strings via + operator:

To concatenate two or more strings, you use the format! macro or the + operator:

let name = "John";
let str = format!("Hello {}", name);

println!("{}", str); // prints "Hello John"

If you want to assemble a string piece by piece, you can use the push_str() method:

let mut greet = "Welcome".to_string();
let name = "John";
greet.push_str(" to AlgoCademy, ");
greet.push_str(name);

println!("{}", greet); // prints "Welcome to AlgoCademy, John"

String slicing

We often want to get a substring of a string. For this, we use a range slice.

&str[startIndex..endIndex] returns the substring starting from startIndex and ending just before endIndex:

let str = "JavaScript";
let substr = &str[2..6];

println!("{}", substr); // prints "vaSc"

The startIndex is a zero-based index at which the slice starts extraction.

The endIndex parameter specifies where to stop (exclusive). The number of characters extracted equals endIndex - startIndex.

If you omit the end index, the slice extracts to the end of the string:

let str = "JavaScript";
let substr = &str[4..];

println!("{}", substr); // prints "Script"

Iterating through the characters:

We can iterate through the characters of a string using a for loop and the .chars() method like this:

let my_str = "Andy";
for c in my_str.chars() {
    println!("{}", c);
}

// This will print the characters 'A', 'n', 'd' and 'y' on different lines

We can also iterate through the elements of a string using indices and a for loop like this:

let my_str = "Andy";
for (i, c) in my_str.chars().enumerate() {
    println!("{}", c);
}

// This will print the characters 'A', 'n', 'd' and 'y' on different lines

Both ways take O(n) time, where n is the length of the string we iterate on.

Assignment
Follow the Coding Tutorial and let's play with some strings.

Hint
Look at the examples above if you get stuck.