Mastering Rust - Second Edition

Borrowing in action

Rust's error diagnostics around the borrowing rules are really helpful when we go against the borrow checker. In the following few examples, we'll see them in various contexts.

Borrowing in functions: As you saw previously, moving ownership when making function calls does not make much sense if you are only reading the value, and is very limiting. You don't get to use the variable after you call the function. Instead of taking parameters by value, we can take them by references. We can fix the previous code example that was presented in the ownership section to pass the compiler without cloning, like so:

// borrowing_functions.rsfn take_the_n(n: &mut u8) {    *n += 2;}fn take_the_s(s: &mut String) {    s.push_str("ing");}fn ...