Rust

12.3    Simplifying Structs

Sometimes, a large, poorly designed struct can lead to borrowing issues. While individual fields might be borrowable independently, borrowing the struct as a whole can block further borrows or block usage of the struct, ultimately preventing other parts of the code from accessing it.

Consider struct A defined in Listing 12.19.

struct A {    f1: u32,    f2: u32,    f3: u32,}  

Listing 12.19     Definition of Struct A Containing Three Fields

Let’s define a few functions that will use the struct instance. Listing 12.20 shows the definitions of these functions.

fn fn1(a: &mut A) -> &u32 {    &a.f2}fn fn2(a: &mut A) -> u32 {    a.f1 + a.f3}fn fn3(a: &mut A) {    let x = fn1(a);    let y = fn2(a);}  

Listing 12.20     Some Functions Defined on ...