How do I pass an array to a function in Rust and change its content?
Rust references (denoted by the & sign) are of two kinds: immutable (&T) and mutable (&mut T). In order to change the value behind the reference, this reference has to be mutable, so you need to:
- accept
&mut [i32]as the function argument, not&[i32] - pass
&mut arrto the function, not&arr:
fn change_value(arr: &mut [i32]) { arr[1] = 10;}fn main() { let mut arr: [i32; 4] = [1, 2, 3, 4]; change_value(&mut arr); println!("this is {}", arr[1]);}You don't need mut arr in change_value's argument because mut there denotes mutability of that variable, not of the data it points to. With mut arr: &[i32] you can reassign arr itself (for it to point to a different slice), but you can't change the data it references.
If you wanted to accept an array instead of a slice, you could also do that:
fn change_value(arr: &mut [i32; 4]) { arr[1] = 10;}See also: