The Rust Programming Language

The Rust Programming Language — References and Borrows — Understanding Values by Reference and Borrows

The pain of use after move errors finally ends!

In one of our previous examples we say an instance where use after move error was observed. Please have a look at the snippet which causes that error:

fn print_years(years: Vec<i32>) {
    for year in years.iter() {
        println!("{}", year);
    }
}

fn main() {
    let years = vec![2001, 2002, 2003, 2004]; // alloc()

    print_years(years); // transfer the ownership of years to print_years()
    print_years(years);
}

You must be aware that the variable years deallocation responsibility is with print_years(). So when the first time the method print_years() is called, years memory is marked as available. So when the method print_years() runs the second time, we get the use after move error.

We understood that this can be solved by making the print_years() return years and we create a new copy of the variable years2 as shown below:

fn print_years(years: Vec<i32>) {
    for year in years.iter() {
        println!("{}", year);
    }
    return years;
}

fn main() {
    let years = vec![2001, 2002, 2003, 2004]; // alloc()

    let years2 = print_years(years); // transfer the ownership of years…