如何實現Rust的Copy特性？

Question

我想在Rust中初始化一個結構數組：

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]; 

當我嘗試編譯時，編譯器抱怨Copy特征未實現：

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

如何實現Copy特征？

Answer 1

您不必自己實現Copy ; 編譯器可以為您派生它：

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

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

請注意，實現Copy每個類型都必須實現Clone 。 Clone也可以派生出來。

Answer 2

只需在你的枚舉之前添加#[derive(Copy, Clone)] 。

如果你真的想要，你也可以

impl Copy for MyEnum {}

derive-attribute在幕后做同樣的事情。