How to fix temporary value dropped while borrowed

Store the temporary value in a variable before borrowing it to extend its lifetime. The compiler drops temporary values at the end of the statement, so you must bind the value to a named variable first to keep it alive for the borrow.

let s = String::from("hello");
let len = calculate_length(&s);

This ensures s lives long enough for calculate_length to borrow it, whereas calculate_length(&String::from("hello")) fails because the temporary string is dropped immediately after the function call.

The "temporary value dropped while borrowed" error happens when you try to use a piece of data that disappears before you are done with it. Think of it like trying to borrow a book from a library that burns the book the moment you ask to check it out. You fix it by keeping the book on a shelf (a variable) first, then borrowing it from there.