Rust Borrowing and References
Borrowing and References
Sometimes you want to use a value without taking ownership of it.
Rust lets you do this using a reference - this is called borrowing:
What is a Reference?
A reference lets you look at a value without owning it.
You create a reference using the & symbol:
Example
let a = String::from("Hello");
let b = &a;
println!("a = {}", a);
println!("b = {}", b);
Try it Yourself »
Since b is only borrowing the value,
a still owns it.
Mutable References
If you want to change a value through a reference, you need to make the reference mut:
Example
let mut name = String::from("John");
let name_ref = &mut name;
name_ref.push_str(" Doe");
println!("{}", name_ref); // John Doe
Try it Yourself »
Note: You can only have one mutable reference to a value at a time!
Why Borrowing is Important
Borrowing helps you reuse values safely, without giving them away.
- It lets you use values without taking ownership
- It avoids cloning, which can be slow for large data
- It makes your programs safer and faster
