Copy
2022/2/17 21:31:00
https://blog.ojisan.io/many-copies-original-sin/
目次
Copy
特質を持たない変数をコピーすると、所有権の移動が発生し、コピー元の変数は使用が不可能になる。
let s1 = String::from("hello");
let s2 = s1;
println!("{}", s1); //error
/*
error[E0382]: borrow of moved value: `s1`
--> src\main.rs:5:16
|
3 | let s1 = String::from("hello");
| -- move occurs because `s1` has type `String`, which does not implement the `Copy` trait
4 | let s2 = s1;
| -- value moved here
5 | println!("{}", s1); //hello
| ^^ value borrowed here after move
*/
Copy
特質を持たない変数を関数に渡すと、所有権の移動が発生し、関数に渡した変数は使用不可能になる。
fn main() {
let s = String::from("hello");
test(s);
println!("{}", s); //error
/*
error[E0382]: borrow of moved value: `s`
--> src\main.rs:4:20
|
2 | let s = String::from("hello");
| - move occurs because `s` has type `String`, which does not implement the `Copy` trait
3 | test(s);
| - value moved here
4 | println!("{}", s); //error
| ^ value borrowed here after move
*/
}
fn test(s:String) {
println!("{}", s); //hello
}