Understand ownership and borrowing
Learn Rust’s core memory-safety model.
- Explain move semantics and pass references to avoid ownership transfer.
Every value in Rust has one owner. When ownership moves, the previous binding is no longer valid. Borrowing with references (&T) lets you read data without taking ownership. Mutable borrows (&mut T) allow controlled updates with strict aliasing rules.
1fn length(text: &String) -> usize {
2 text.len()
3}
4
5fn main() {
6 let message = String::from("rustacean");
7 let size = length(&message);
8 println!("{}", size);
9}9
Ownership and borrowing eliminate many memory bugs without garbage collection. Start by asking: “Who owns this value now?” and “Do I need ownership, or just a borrow?”.
Key takeaways
Explain move semantics and pass references to avoid ownership transfer.
Rust uses types and ownership rules to prevent common bugs.
Small experiments build intuition quickly.
Lesson quiz
5 questions · pass with 4 correct · up to 50 XP
Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.
Practice: write Rust
These run for real. Write the program, press Run tests, and read what the compiler tells you - learning to read compiler messages is half of learning C.
Borrow and print length
Complete word_length to take a borrowed String and return its length, then print it.
- Fixed word
Rust lessons are authored for modern stable Rust; exercises run on Rust 1.82 via Wandbox, a free public service. Your source code and test input are sent to that service.
Questions about this lesson
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