生命周期 - 结构体
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小牛编辑
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2023-12-01
在结构体中标注生命周期也和函数的类似:
// 一个 `Borrowed` 类型,含有一个指向 `i32` 类型的引用。
// 指向 `i32` 的引用必须比 `Borrowed` 寿命更长。
// (原望:A type `Borrowed` which houses a reference to an
// `i32`. The reference to `i32` must outlive `Borrowed`.)
#[derive(Debug)]
struct Borrowed<'a>(&'a i32);
// 和前面类似,这里的两个引用都必须比这个结构体长寿。
#[derive(Debug)]
struct NamedBorrowed<'a> {
x: &'a i32,
y: &'a i32,
}
// 一个枚举类型,不是 `i32` 类型就是一个指向某个量的引用。
//(原文: An enum which is either an `i32` or a reference to one.)
#[derive(Debug)]
enum Either<'a> {
Num(i32),
Ref(&'a i32),
}
fn main() {
let x = 18;
let y = 15;
let single = Borrowed(&x);
let double = NamedBorrowed { x: &x, y: &y };
let reference = Either::Ref(&x);
let number = Either::Num(y);
println!("x is borrowed in {:?}", single);
println!("x and y are borrowed in {:?}", double);
println!("x is borrowed in {:?}", reference);
println!("y is *not* borrowed in {:?}", number);
}
参见:
structs