对象安全的 Clone 特性

此 crate 提供了一个 DynClone 特性，可用于 trait 对象，以及一个 clone_box 函数，可以克隆任何大小的或动态大小的 DynClone 实现。实现了标准库的 std::clone::Clone 特性的类型可以自动用于 DynClone 特性对象。

clone_box 的签名是

fn clone_box<T>(t: &T) -> Box<T>
where
    T: ?Sized + DynClone

示例

use dyn_clone::DynClone;

trait MyTrait: DynClone {
    fn recite(&self);
}

impl MyTrait for String {
    fn recite(&self) {
        println!("{} ♫", self);
    }
}

fn main() {
    let line = "The slithy structs did gyre and gimble the namespace";

    // Build a trait object holding a String.
    // This requires String to implement MyTrait and std::clone::Clone.
    let x: Box<dyn MyTrait> = Box::new(String::from(line));

    x.recite();

    // The type of x2 is a Box<dyn MyTrait> cloned from x.
    let x2 = dyn_clone::clone_box(&*x);

    x2.recite();
}

此 crate 包含一个宏，用于生成基于 dyn_clone::clone_box 的 impl std::clone::Clone for Box<dyn MyTrait> 实现

// As before.
trait MyTrait: DynClone {
    /* ... */
}

dyn_clone::clone_trait_object!(MyTrait);

// Now data structures containing Box<dyn MyTrait> can derive Clone:
#[derive(Clone)]
struct Container {
    trait_object: Box<dyn MyTrait>,
}

许可协议