如何实现Rust的Copy特性？

Question

我想在Rust中初始化一个结构数组:

enum Direction {
    North,
    East,
    South,
    West,
}

struct RoadPoint {
    direction: Direction,
    index: i32,
}

// Initialise the array, but failed.
let data = [RoadPoint { direction: Direction::East, index: 1 }; 4]; 

当我尝试编译时,编译器抱怨该Copy特征未实现:

error[E0277]: the trait bound `main::RoadPoint: std::marker::Copy` is not satisfied
  --> src/main.rs:15:16
   |
15 |     let data = [RoadPoint { direction: Direction::East, index: 1 }; 4]; 
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `main::RoadPoint`
   |
   = note: the `Copy` trait is required because the repeated element will be copied

如何Copy实施这一特性？

Answer 1

你不必Copy自己实施; 编译器可以为您派生它:

#[derive(Copy, Clone)]
enum Direction {
    North,
    East,
    South,
    West,
}

#[derive(Copy, Clone)]
struct RoadPoint {
    direction: Direction,
    index: i32,
}

请注意,实现的每个类型也Copy必须实现Clone.Clone也可以派生出来.

Answer 2

只是#[derive(Copy, Clone)]在你的枚举之前.

如果你真的想要,你也可以

impl Copy for MyEnum {}

derive-attribute在幕后做同样的事情.