rust - 如何为元组结构成员分配默认值

Question

如何自动为元组结构成员分配默认值

struct A(f64, i32);

fn main() {
    let mut a: A; // expect a.0 = 0.0, a.1 = 0
    // even below 2 line code doesn't compile
    // a.0 = 1.2;
    // a.1 = 3;

    println!("{}, {}", a.0, a.1);
}

但是我遇到了以下错误

error[E0381]: used binding `a` isn't initialized
 --> src/main.rs:5:24
  |
4 |     let mut a: A; // expect a.0 = 0.0, a.1 = 0
  |         ----- binding declared here but left uninitialized
5 |     println!("{}, {}", a.0, a.1);
  |                        ^^^ `a.0` used here but it isn't initialized
  |

Answer 1

添加#[derive(Default)]并使用A::default进行初始化(或默认::default()):

#[derive(Default)]
struct A(f64, i32);

fn main() {
    let mut a = A::default(); // expect a.0 = 0.0, a.1 = 0
    
    println!("{}, {}", a.0, a.1);
}