Strings: Words & Sentences

Vectors hold numbers and things — but how do we hold words? 📝 In Rust, a chunk of text is called a string, and it works a lot like a backpack for letters. You can keep snapping more words onto the end.

The Big Idea A String is text that can grow. A &str (say "string slice") is a borrowed peek at some text that stays the same size.

Building a sentence

You start a growable String with String::from. Then you snap on more words using push_str. It’s like adding train cars one at a time. 🚂

Think of it like this… A &str is like reading words off a poster on the wall — you can look, but you can't change it. A String is your own notebook where you keep writing more. ✏️

Gluing words together

You can join text with format!, which builds a brand-new sentence for you. You can also check how long text is with .len(), and walk through each letter with .chars().

fn main() {
    let mut greeting = String::from("Hello");
    greeting.push_str(", friend");

    let name = "Ferris";
    let sentence = format!("{}! I am {} 🦀", greeting, name);

    println!("{}", sentence);
    println!("That has {} letters in it.", sentence.len());
}

Ferris says: Rust text is stored as UTF-8, which is a fancy way of saying it can hold letters from any language — and even emoji like 🦀 and 🎉!

Watch out! .len() counts the tiny pieces of data (bytes), not always the number of emoji or fancy letters. An emoji can take up several bytes by itself!

Try this! Change "Ferris" to your own name and press ▶ Run. The sentence and the letter count will both change!

Quick quiz

Which one adds more text onto the end of a String?

Right! push_str snaps more words onto your growing String. 🚂

You learned… A String is growable text and a &str is a borrowed peek. You build text with String::from and push_str, glue it with format!, and Rust uses UTF-8 so emoji work. Next up: matching pairs with Hash Maps! 🔑