Summary - Strings

Combine String and &str to build a greeting message.

Strings summary

&str is borrowed and immutable; String is owned and growable. Creating: String::from, to_string, String::with_capacity. Appending: push_str, push, +=, + (takes ownership of the left side). Formatting: format!. Length: len counts bytes, chars().count() characters.

Case and whitespace

Common methods return a new value; they don't change the original text:

let s = "  Merhaba Rust  ";
println!("[{}]", s.trim());          // [Merhaba Rust]
println!("{}", s.to_uppercase());     //   MERHABA RUST
println!("{}", s.contains("Rust"));   // true
println!("{}", s.replace("Rust", "Go"));

to_uppercase applies Unicode rules: "ş".to_uppercase() → "Ş".

Exercise Clean and capitalize

Write fn temizle(s: &str) -> String: remove leading/trailing whitespace with trim and capitalize with to_uppercase. Print the result of temizle(" şeker ") and its length (len).

Show example solution

fn temizle(s: &str) -> String {
    s.trim().to_uppercase()
}

fn main() {
    let t = temizle("  şeker  ");
    println!("{} {}", t, t.len());
}

Test yourself

With <code>let s = String::from("Rust"); let k = &s[0..1];</code>, what is k?
- A compile error
- "R" (&str)
- 'R' (char)
- 82
Show answer

"R" (&str) — Slicing with a byte range gives a &str; if the range falls in the middle of a character, it panics at run time.

Trim whitespace

let girdi = "  42 \n";
let temiz = girdi.____();  // "42"

Show answer

let girdi = "  42 \n";
let temiz = girdi.trim();  // "42"

Group summary

&str

Borrowed view
String

Owned text
format!

Formatted String
chars().count()

Character count

Next lesson: Project skeleton

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies