How can I do a mutable borrow in a for loop?

问题

I tried:

let mut vec = [1,2,3];

for mut x in &vec { *x=3; }
for mut &x in &vec { x=3; }
for mut *x in &vec { x=3; }
for mut x in mut &vec { *x=3; }
for mut x in &(mut vec) { *x=3; }

None of these work; how should I do it?

回答1:

You may want to re-read The Rust Programming Language section on mutability:

You can also create a reference to it, using &x, but if you want to use the reference to change it, you will need a mutable reference:

let mut x = 5;
let y = &mut x;

fn main() {
    let mut array = [1, 2, 3];

    for x in &mut array {
        *x = 3;
    }
}

See also:

• What's the difference in `mut` before a variable name and after the `:`?

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Note that your variable is not a vector. It is an array.

来源：https://stackoverflow.com/questions/39622783/how-can-i-do-a-mutable-borrow-in-a-for-loop