27°

rust clone 的一个小注意点

先看代码A:

#[derive(Debug, Clone)]
struct Test(i32);

fn main() { let mut x = Test(1); let a = &x; let b = a.clone(); let c: i32 = b; }

这段代码报的错是:

  |
8 |     let c: i32 = b;
  |                  ^ expected i32, found struct `Test`
  |
  = note: expected type `i32`
             found type `Test`

再看代码B:

#[derive(Debug)]
struct Test(i32);

fn main() { let mut x = Test(1); let a = &x; let b = a.clone(); let c: i32 = b; }

报错是:

  |
8 |     let c: i32 = b;
  |                  ^ expected i32, found &Test
  |
  = note: expected type `i32`
             found type `&Test`

两段代码的唯一区别就是结构体Test,A实现Clone,B没有实现Clone。

结论就是:如果一个引用,它引用的对象如果不能clone,就clone引用,如果能clone,就直接clone对象并返回。

本文由【wmzsonic】发布于开源中国,原文链接:https://my.oschina.net/u/855913/blog/3072629

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